Bryant Thermostat Q674 Users Manual 60 2485 T874 Multistage Thermostats And Subbases

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2015-02-02

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Application
Features
Specifications
- Super Tradeline®/Tradeline® Models
Installation
Settings
Checkout
Calibration
- Thermostat
- Thermometer
Understanding Circuits
- Tracing Method:
Operation
Cross Reference
Wiring Diagrams

PRODUCT DATA

60- 248

® U.S. Re

istered Trademark

Cop

well • All Ri

hts Reserved

T874 Multistage Thermostats

and Q674 Subbases

APPLICATION

These thermostats and subbases provide low volta

e control

of multista

e heatin

and coolin

stems, includin

heat

pump s

stems.

FEATURES

• T874 Thermostat has silent, dust-free mercury

switches operated by coiled bimetal elements.

• Heat anticipator(s) are adjustable or fixed cooling

anticipator(s) are fixed.

• Individual heat and cool levers and scales (most

models) for temperature setting located on top of

thermostat case.

• Cover thermometer on most T874 Multistage

Thermostat models.

• Locking cover and locking lever screws available for

T874 Multistage Thermostats.

• Versaguard™ Thermostat Guard or custom key lock

thermostat guards available for T874 Multistage

Thermostats.

• T874 Thermostat requires a Q674 Subbase.

• Q674 Subbase provides system and fan switching,

wiring terminals and mounting base for T874

Multistage Thermostat.

• Adapter plate available for mounting Q674 on wall or

horizontal outlet box.

• Light-emitting diodes (LEDs) located on subbase for

easy reference.

• Up to three stages each of heating and cooling control

possible.

• Models with setpoint restrictions and locking cover

with no thermometer available for Department of

Defense (DoD) and other special applications.

• Outdoor reset used on some models to improve

thermal performance. Contents

Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Checkout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Understanding Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Cross Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Wiring Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—82

ORDERING INFORMATION

When purchasin

replacement and modernization products from

our TRADELINE® wholesaler or distributor, refer to the

TRADELINE® Catalo

or price sheets for complete orderin

number.

ou have additional

uestions, need further information, or would like to comment on our products or services, please write or

phone:

1. Your local Home and Buildin

Control Sales Office

(

check white pa

es of

our phone director

2. Home and Buildin

Control Customer Relations

Hone

well, 1885 Dou

las Drive North

Minneapolis, Minnesota 55422-4386

(

800

)

328-5111

In Canada—Hone

well Limited/Hone

well Limitée, 35 D

namic Drive, Scarborou

h, Ontario M1V 4Z9.

International Sales and Service Offices in all principal cities of the world. Manufacturin

in Australia, Canada, Finland, France,

German

, Japan, Mexico, Netherlands, Spain, Taiwan, United Kin

dom, U.S.A.

SPECIFICATIONS

IMPORTANT

The specifications given in this publication do not

include normal manufacturing tolerances. Therefore,

this unit may not exactly match the listed specifica-

tions. This product is tested and calibrated under

closely controlled conditions, and some minor differ-

ences in performance can be expected if those con-

ditions are changed.

Super Tradeline®/Tradeline® Models

SUPER TRADELINE controls offer features not available on

TRADELINE or standard models, and are desi

ned to replace

a wide ran

e of Hone

well and competitive controls.

TRADELINE models are selected and packa

ed to provide

ease of stockin

, ease of handlin

, and maximum

replacement value. Specifications of SUPER TRADELINE

and TRADELINE controls are the same as those of standard

models except as noted below.

Super Tradeline Models

T874 THERMOSTAT

T874D Thermostat. Provides two sta

es of heatin

and two

sta

es of coolin

. Use with Q674A-F Subbases.

Y594D

(

T874D/Q674E/TG504A

)

Thermostat/Subbase/ke

lock cover packa

e. Provides two sta

es of heatin

and

two sta

es of coolin

. Includes a ke

lock cover for set-

point protection.

Y594G

(

T874G/Q674F

)

Thermostat/Subbase packa

e for

heat pump. Provides two sta

es of heatin

and one sta

of coolin

. Automatic chan

eover in heat or cool mode.

Available in bei

e or Premier White® color.

Y594R

(

T874R/Q674L

)

Thermostat/Subbase packa

e for

heat pump. Provides two sta

es of heatin

and one sta

of coolin

. Manual chan

eover in heat or cool mode. Avail-

able in bei

e or Premier White® color.

SUPER TRADELINE FEATURES:

•SUPER TRADELINE packa

e with cross reference label

and special instruction sheet.

•SUPER TRADELINE model supplied with lockin

lever and

lockin

cover accessories.

•Includes ad

ustable temperature lockin

stops.

•T874D replaces T874A-F TRADELINE or standard models.

Tradeline Models

T874 THERMOSTAT

•T874 TRADELINE models provide sta

ed heat and/or cool

operation. See Table 1.

Table 1. Heating and Cooling Stages.

•T874A-F are standard models.

TRADELINE FEATURES:

•TRADELINE packa

e with cross reference label and

special instruction sheet.

•T874A,C model available with factor

stops for DoD

applications.

•T874A,C model available with ad

ustable temperature

lockin

stops.

Q674 SUBBASE

Q674 switchin

subbases provide s

stem and fan switchin

See Table 2.

Table 2. System and Fan Switching.

TRADELINE FEATURE:

•TRADELINE packa

e with cross reference label and

special instruction sheet.

•Q674A-E,G are standard

(

non-heat pump

)

models.

Q674F,J,L are heat pump models.

Models ABCDEF

Heatin

Sta

es 1122—2

Coolin

Sta

es 12122—

Q674 System Fan

A Heat-Auto-Cool Auto-On

B Heat-Off-Cool Auto-On

C Off-Auto Auto-On

D None None

E Off-Heat-Auto-Cool Auto-On

F Em. Ht.-Off-Heat-Auto-Cool Auto-On

G Off-Auto None

J Em. Ht.-Auto-Off Auto-On

L Em. Ht.-Heat-Off-Cool Auto-On

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

3 60-2485—8

Standard Models

T874 THERMOSTATS

Models: See Table 3.

Electrical Rating: 24 to 30 Vac.

Switching: Coiled bimetal elements operate mercur

switches.

Temperature Adjustment: Heatin

and coolin

settin

levers, with separate scales located on top of thermostat

base. Common lever for heatin

and coolin

on T874R;

one coolin

lever on T874E,V; and one heatin

lever on

T874F,Q.

Dimensions: See Fi

. 1.

Temperature: Scale Ran

e: 42° to 88°F

(

6° to 31°C

)

stan-

dard; optional ran

es available.

Thermometer Range: 42° to 88°F

(

6 to 31°C

)

Changeover Differential: 4°F

(

2°C

)

minimum between heat-

and coolin

(

5°F [3°C] on T874W

)

. Levers can be set

apart for

reater separation.

Interstage Differential:

Standard Models: Mechanical differential is 1°F

(

0.6°C

)

between heatin

or coolin

sta

es; operatin

differential is

approximatel

1.9°F

(

1°C

)

between sta

es in heatin

coolin

Special Models: See Table 3.

Finish: Bei

e or Premier White® finish.

Mounting Means: T874 Multista

e Thermostat mounts on

Q674 Subbase. Subbase mounts horizontall

on wall or

outlet box. Mounts on vertical outlet box with optional

193121A Adapter Plate Assembl

Fig. 1. T874 Thermostat and Q674 Subbase dimensions in in. (mm).

Optional Specifications (T874 Only):

Temperature scale ran

es are 40° to 75°F

(

4° to 24°C

)

heat-

and 75° to 90°F

(

24° to 32°C

)

coolin

with stop; 44° to

68°F

(

7° to 20°C

)

heatin

, 80° to 86°F

(

27° to 30°C

)

cool-

; 6° to 29°C

(

43° to 85°F

)

Celsius scale; 3°to 22°C

(

38°

to 72°F

)

and 26° to 32°C

(

78° to 90°F

)

coolin

with stop.

Nonad

ustable factor

-added stop limits heatin

setpoint to

72°F

(

22°C

)

maximum and coolin

setpoint to 78°F

(

26°C

)

minimum.

OEM customer personalization.

Lockin

cover and lockin

lever

(

see Thermostat Accesso-

ries

)

Thermostat cover without thermometer.

ustable lockin

temperature stops.

Volta

e heat anticipation for first or second sta

e heat or both.

See Table 3.

Fast c

clin

on heatin

sta

(

)

for electric heat applications.

C815A Outdoor Thermistor for improved performance on

specified models.

Thermostat Accessories:

Lockin

Cover and Lockin

Lever Assembl

: Part no.

194559R with thermometer; 194559S without thermome-

ter. See Fi

. 2. Includes cover, screws, and Allen wrench

for lockin

cover. The screws must be used to assure

proper operation.

ustable Lever Stop: Part no. 4074ECK; includes lever stop

and screws.

Universal Versa

uard™ Thermostat Guard: Includes wall-

plate, rin

base,

uard cover, tumbler lock, two ke

s and

optional Hone

well lo

o insert. Double-wall construction

provides extra measure of tamper-resistance. Tamper-

resistant lock; ke

cannot be removed without bein

locked position. Vents in

uard base allow airflow for opti-

mum thermostat performance. See form 68-0104 for more

information.

—TG511A1000: Clear cover.

—TG511B1008: Opa

ue cover.

—TG511D1004: Painted steel

(

off-white

)

cover. See

. 2.

M5849

FAN

AUTO ON OFF EM. HT. HEAT AUTO COOL

(38)

(87)

SUBBASE

THERMOSTAT MOUNTED

ON SUBBASE

SIDE

50 60 70 80

50 60 70 80 50 60 70 80

HEAT COOL

FAN

AUTO ON OFF EM. HT. HEAT AUTO COOL

(89)

FRONT

2-3/16 (56)

1-7/8 (48)

3-1/2

5-1/8 (130)

1-1/2

3-9/32 (83)

3-7/16

3/8 (10)

5-5/8 (143)

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—84

Lock Cover: Part no. TG504A replaces existin

T874

cover. Mounts on T874 base and covers thermostat set-

tlin

levers and subbase switches. Includes LED window

and two ke

s. Should not be used with 193121A Adapter

Plate.

—TG504A1025: Blank face, internal thermometer.

—TG504A1033: External thermometer. See Fi

. 2.

Fig. 2. T874 Thermostat accessories.

Table 3. T874 Thermostat Specifications.

Models and Options Replaces Applications

System Stages

Anticipation

Heating (Adj) Cooling (Fixed)

Heat Cool Other Stage 1 Stage 2 Stage 1 Stage 2

T874A—Standard and TRADELINE®.

—72°F/78°F

(

22°C/26°C

)

setpoint

stops with lockin

cover.

—Ad

ustable anticipator set 0.4A.

—Ad

ustable lockin

temperature

stops

(

TRADELINE®

)

—72°F/78°F

(

22°C/26°C

)

setpoint

stops with lockin

cover, no

thermometer

(

for DoDa

)

T872A Standard 1 1 —0.1-1.2A —0-1.5A —

T874B—Standard and TRADELINE. T872B Standard 1 2 —0.1-1.2A —0-1.2A 0-1.0A

T874C—Standard and TRADELINE.

—72°F/78°F

(

22°C/26°C

)

set stops

with lockin

cover, no thermometer

(

for DoDa

)

—12°F

(

7°C

)

differential between

H1 and H2 sta

(

T874C1125

)

T872C Standard 2 1 —0.1-1.2A 0.1-1.2A 0-1.5A —

—Fast c

clin

.0.12-

0.6A 0.12-

0.6A

T874D—Standard and SUPER

TRADELINE®.

—Ad

ustable lockin

temperature

stops

(

SUPER TRADELINE

)

T872D Standard 2 2 —0.1-1.2A 0.1-1.2A 0-1.2A 0-1.0A

T874E—Standard and TRADELINE. T872E 2-Sta

e Cool —2—— —0-1.2A 0-1.0A

T874F—Standard and TRADELINE.

—Lockin

cover. T872F 2-Sta

e Heat 2 ——0.1-1.2A 0.1-1.2A ——

aDepartment of Defense.

bChan

eover sta

e operates with heatin

cFixed volta

e t

pe anticipation.

dChan

eover sta

e operates with heatin

; a secondar

chan

eover is provided in coolin

switch.

eProvides ni

ht setback used with standard T874 and timer-operated remote switchin

fManual chan

eover sta

e—use Q674B,L subbase.

gChan

eover sta

e operates with coolin

.Q674 Subbases

194559R Locking Cover

with Thermometer

Allen Wrench

TG511D1004 Includes

Painted Steel Cover,

Opaque Base and Wallplate

TG504A1033 Key Lock

Cover with External

Thermometer

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

5 60-2485—8

Models:

See Table 4.

Electrical Ratings:

Switch Contacts: 2.5A at 30 Vac

(

7.5A inrush

)

LED Li

hts

(

Optional

)

: 30 Vac.

Switches: Two slide switches

(

one switch on Q674G and K;

no switches on Q674D

)

operated b

levers. Switch position

is shown on scaleplate.

Mounting: Desi

ned to mount horizontall

on an outlet box

or the wall. Adapter plate assembl

available for mountin

on a vertical outlet box

(

see Subbase Accessor

Finish: Dark brown or

Dimensions in in. (mm): 3-1/2

(

)

hei

ht; 5-5/8

(

143

)

width;

5/16

(

)

depth. See Fi

. 1.

Table 4. Q674 Subbase Specifications.

—Fast c

clin

. Electric Heat 0.12-

0.6A 0.12-

0.6A

T874G—Heat pump, cool

chan

eover, with fast c

clin

.T872G Heat Pump or

Standard 21

1b0-1.0Ac0.1-1.2A 0-1.0A —

—Fixed anticipator for H2. 0.1-1.5A

—Fast c

clin

.0.12-

0.6A

T874H—Use with Q674C. T872H Heat Pump or

Standard 11

1b0-1.0Ac—0-1.0A —

T874J—Heat pump. None Heat Pump 2 1 2d0-1.0Ae0-1.5Ac0-1.0Ac—

T874K—Heat pump. None Heat Pump 2 1 1b0.1-1.2A 0-1.5Ac0-1.5A —

T874L—Heat pump. None Heat Pump 2 1 —0.1-1.2A 0.1-1.2A 0-1.5A —

T874N—Heat pump, heat

chan

eover. T872N Heat Pump 2 1 1b0.1-1.2A 0.1-1.2A 0-1.0A —

T874P—Heat pump. None Heat Pump 2 1 —0.1-1.2A 0.1-1.2A 0-1.5A —

T874Q—Ni

ht setback heatin

. T872Q Standard 1e——0.1-1.2A ———

T874R—Heat pump. T872R Heat Pumpf21—0-1.5Ac0.1-1.2A 0-1.5A —

T874S—Two-speed compressor heat

pump. None Heat Pump 2 2 1

0-1.2Ac0-1.2Ac0-1.2A 0-1.0A

T874V—Standard. None Standard —1—— —0-1.5A —

T874W—Heat pump and standard.

—Ni

ht setback heatin

.T872W Heat Pump or

Standard 32—0-1.2Ab0-1.2Ac,d 0-1.2A 0-1.0A

aDepartment of Defense.

bChan

eover sta

e operates with heatin

cFixed volta

e t

pe anticipation.

dChan

eover sta

e operates with heatin

; a secondar

chan

eover is provided in coolin

switch.

eProvides ni

ht setback used with standard T874 and timer-operated remote switchin

fManual chan

eover sta

e—use Q674B,L subbase.

gChan

eover sta

e operates with coolin

.Q674 Subbases

Models and Options Replaces Application

Switch Positions

Use WithSystem Fan

Q674A—Standard and TRADELINE®.

—Indicator LEDs. Q672A Standard HEAT-AUTO-COOL AUTO-ON T874A-D

Q674B—Standard and TRADELINE. Q672B Standard HEAT-OFF-COOL AUTO-ON T874A-D

—Provision for fan rela

operation from Heat Pump T874G,H,L,R

external fan switch

(

isolate G terminal

)

. OVERRIDE-HEAT- AUTO-ON T874P

—Indicator LEDs. OFF-COOL

Q674C—Standard and TRADELINE. Q672C Standard OFF-AUTO AUTO-ON T874A-H,W

—Indicator LEDs. Heat Pump OVERRIDE-AUTO- AUTO-ON T874K,L,N

OFF T874P

Q674D—Standard and TRADELINE.

—For use when subbase switchin

is not

uired.

Q672D Standard None None T874A-F

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—86

Optional Specifications (Q674 Only):

Models available with up to four LEDs; for example, LEDs can

show EM. HT, AUX. HT, SERVICE, CHECK, FILTER, and

LOCKOUT. See Fi

. 3.

stem switchin

marked HEAT-OFF/RESET-COOL for s

tems re

uirin

impedance rela

reset. Available on Q674B

onl

G terminal isolated on heatin

to provide fan rela

operation

from external low volta

e fan switch

(

Q674B onl

Auto fan operation on both heat and cool.

L terminal is used for s

stem monitorin

devices.

Common R terminal for heatin

/coolin

Chan

eover in cool or heat mode for heat pumps.

Auto fan in EM.HT. for heat pumps.

Subbase Accessory: 193121A Adapter Plate Assembl

for

mountin

on vertical outlet box. Assembl

includes adapter

rin

and cover plate. Use to cover wall marks from

replaced thermostat.

Fig. 3. Heating, cooling levers and system LED indicators.

Q674E—Standard and TRADELINE. Q672E Standard OFF-HEAT-AUTO-

COOL AUTO-ON T874A-D

Q674F—Two LED models.

—EM.HT. li

ht. Q672F Heat Pump OFF-EM.HT.-HEAT-

AUTO-COOL AUTO-ON T874C,D,G,N,S

—Provision for AUTO fan operation in

EM.HT. OFF-COOL-AUTO-

HEAT-EM.HT. AUTO-ON

Q674G—O and B terminals. Q672G Standard OFF-AUTO None T874A-F

Q674J—Provision for AUTO fan operation Q672J Heat Pump EM.HT.-AUTO-OFF AUTO-ON T874A,D,G,J

in EM.HT. EM.HT.-ON-OFF AUTO-ON

—Provision for outdoor thermistor. SUPL.HT.-ON-OFF AUTO-ON

Q674K—Standard. Q672K Standard OFF-HEAT-AUTO-

COOL None T874F

OFF-WOOD-WOOD/

OIL-OIL None

Q674L—Provision for AUTO fan operation in

EM.HT. Q672L Heat Pump EM.HT.-HEAT-OFF-

COOL AUTO-ON T874R,W

—Indicator LEDs. SUPL.HT.-HEAT-

OFF-COOL AUTO-ON

Q674N—Standard. Q672N Evaporative

Cooler EVAP-COOL-OFF-

HEAT AUTO-ON T874C

Q674P—Standard. Q672P Heat Pump SUPL.HT.-HEAT-

COOL AUTO-ON T874G

Q674Q—Standard. None Fan Coil HEAT-OFF-COOL LO-MED-HI-

ON T874A

Q674R—Standard.

—International s

mbols. None Fan Coil OFF-COOL LO-HI-

CONT. T874V

Q674S—Indicator LED. None Standard HEAT-COOL None T874C

T874 Thermostat with

One Setpoint Lever Q674 Subbase

with Four LEDs

T874 Thermostat with

Separate

Heatin

and Coolin

Levers

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

7 60-2485—8

MERCURY NOTICE

This control contains mercur

in a sealed tube. Do

not

place control in the trash at the end of its useful life.

If this control is replacin

a control that contains

mercur

in a sealed tube, do

not

place

our old control

in the trash.

Contact

our local waste mana

ement authorit

for

instructions re

ardin

rec

clin

and the proper

disposal of this control, or of an old control containin

mercur

in a sealed tube. If

ou have

uestions, call

the Hone

well Customer Response Center at

1-800-468-1502.

INSTALLATION

When Installing this Product…

1. Read these instructions carefull

. Failure to follow them

could dama

e the product or cause a hazardous condi-

tion.

2. Check the ratin

iven on the product to make sure the

product is suitable for

our application.

3. Installer must be a trained, experienced service techni-

cian.

4. After installation is complete, check out product opera-

tion as provided in these instructions.

CAUTION

Hazardous Voltage.

Can damage heating/cooling system.

1. Disconnect power suppl

before be

innin

instal-

lation to prevent electrical shock or e

uipment

dama

2. Do

not

short across coil terminals on rela

. This

can burn out thermostat heat anticipator.

3. To prevent interference with the thermostat link-

e, keep wire len

th to a minimum and run wires

as close as possible to the subbase.

4. Do

not

overti

hten thermostat captive mountin

screws because dama

e to subbase threads can

result.

IMPORTANT

An incorrectly leveled thermostat will cause the tem-

perature control to deviate from setpoint. It is not a

calibration problem.

Location

Install the thermostat about 5 ft

(

1.5m

)

above the floor in an

area with

ood air circulation at avera

e temperature.

Do not mount the thermostat where it can be affected b

—drafts or dead spots behind doors, in corners or under

cabinets.

—hot or cold air from ducts.

—radiant heat from the sun, fireplace, or appliances.

—concealed pipes and chimne

—unheated

(

uncooled

)

areas such as an outside wall behind

the thermostat.

Mount Subbase

The subbase can be mounted on a vertical outlet box,

horizontal outlet box or directl

on the wall.

1. If the subbase is mounted on a vertical outlet box, order

Hone

well part no. 193121A Adapter Assembl

. See

. 4. The assembl

includes an adapter rin

, two

screws and a cover plate to cover marks on the wall.

Install the rin

and cover plate on the vertical outlet box.

NOTE: For a wall installation, hold subbase in position and

mark holes for anchors. See Fi

. 5. Wall anchors

must be obtained from local hardware store. Be

careful that the wires do not fall back into the wall

openin

. Set aside subbase. Drill four

3/16 in.

(

4.8 mm

)

holes and

entl

tap anchors into

the holes until flush with the wall.

2. Pull wires throu

h the cover plate

(

if used

)

and subbase

cable openin

. See Fi

. 6.

3. Secure the cover plate

(

if used

)

and subbase with the

screws provided. Do not full

hten the subbase

screws.

Level the subbase usin

a spirit level, see Fi

. 7, and firml

hten subbase mountin

screws. The subbase mountin

holes provide for minor out-of-level ad

ustments.

Fig. 4. Installing Q674 Subbase on outlet box.

M6009

VERTICAL

OUTLET

BOX

ADAPTER

RING

COVER

PLATE

MOUNTING

SCREWS (2)

SUBBASE

MOUNTING SCREWS (2)

HORIZONTAL

OUTLET

BOX

1 NOT INCLUDED WITH UNIT.

2 ACCESSORY PART AVAILABLE (193121A).

THERMOSTAT

CAPTIVE

MOUNTING SCREWS (2)

50 60 70 80

HEATCOOL

THERMOSTAT

COVER

50 60 70 80

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—88

Fig. 5. Installing Q674 Subbase on wall.

Fig. 6. Subbase components and leveling procedure.

Wire Subbase

Disconnect power suppl

before be

innin

installation to

prevent electrical shock or e

uipment dama

All wirin

must compl

with local electrical codes and

ordinances.

IMPORTANT

Use 18 gauge, solid-conductor wire whenever possi-

ble. If using 18 gauge stranded wire, no more than

10 wires can be used. Do not use larger than

18 gauge wire.

Follow e

uipment manufacturer wirin

instructions when

available. To wire subbase, proceed as follows:

1. Connect the s

stem wires to the subbase as shown in

the applicable dia

ram. A letter code is located near

each terminal for identification. T

pical terminal desi

nation and wirin

connections are listed in Table 5. The

terminal barrier permits strai

ht or wraparound wirin

connection. See Fi

. 7. The subbase can re

uire one or

umpers that ma

or ma

not be factor

-supplied.

See Fi

. 8 and the wirin

dia

rams for specific terminals

to be

umpered.

Fig. 7. Barrier configuration.

CAUTION

Equipment Damage Hazard.

Never install more than one wire per terminal unless

usin

factor

-supplied

umper with spade terminal.

2. Firml

hten each terminal screw.

3. Fit wires as close as possible to the subbase. Push

excess wire back into the hole.

4. Plu

hole with nonflammable insulation to prevent drafts

from affectin

the thermostat.

WIRES THROUGH

WALL OPENING

WALL

ANCHORS

(2)

SUBBASE

MOUNTING

SCREWS (2)

M926

MOUNTING

HOLES

SPIRIT LEVEL

M927

WIRING

TERMINAL THERMOSTAT

CABLE OPENING

TO SPRING FINGER

CONTACTS ON

THE THERMOSTAT

(

UP TO 12

)

MOUNTING

HOLES (4)

POST FOR

MOUNTING

THERMOSTAT (2)

FOR STRAIGHT

INSERTION–

STRIP 5/16 IN. (8 MM)

FOR WRAPAROUND–

STRIP 7/16 IN. (11 MM)

SUBBASE TERMINAL SCREW M928

BARRIER

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

9 60-2485—8

Fig. 8. Jumper adjacent terminals for special system hookup using stripped wire 3/4 in. (19 mm).

For nonadjacent terminals and using jumper wire supplied with subbase.

Table 5. Terminal Designationsa

Standard Terminal

Designation Alternate Designations or

Customer Specials Typical Connection

BHeatin

damper motor; chan

eover valve

EKEmer

enc

heat rela

G F Fan rela

coil

stem monitor

ORCoolin

damper motor; chan

eover valve

R V Power connection to transformer

(

internall

connected for heatin

and coolin

RC Power connection to coolin

transformer

RH Power connection to heatin

transformer

W1 H1, R3 Sta

e 1 heatin

control

W2 H2, Y, R4 Sta

e 2 heatin

control

W3 Sta

e 3 heatin

controlb

Y1 C1, M Sta

e 1 coolin

control

Y2 C2 Sta

e 2 coolin

control

Y3 Sta

e 3 coolin

control

XX1,X2,CClo

ed filter switch or common connection

T A Outdoor thermistor

L, C, H HSII control panel

PDefrost

O Momentar

circuit, chan

eover

A, A1, A2, Z, C, L LEDs

aOther terminal desi

nations can be used that are not listed on this table. Refer to the hookup drawin

and internal schematic

for exact connections.

bW3 controls the auxiliar

heat like W2, and allows addin

additional sta

es of auxiliar

heat with outdoor thermostats while

maintainin

the proper second sta

e anticipation.

M5899

1 TWO ADJACENT TERMINALS SHOWN JUMPERED ARE FOR EXAMPLE ONLY. COMPARE WIRING

DIAGRAM AND SUBBASE TO IDENTIFY TERMINALS TO BE JUMPERED.

JUMPER WIRE

(SUPPLIED WITH SOME MODELS)

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—810

Outdoor Disconnect

The National Electrical Code re

uires the installation of a

disconnect switch w

ithin

ht of the outdoor unit of an air

conditioner or heat pump. The switch is for the safet

of an

technician workin

on the unit. The technician can assure that

the unit

remains

unpowered.

Install and Adjust Stop Brackets

The stop brackets should be installed onl

if there is a need to

restrict the ad

ustable ran

e of the heatin

and coolin

temperature setpoint levers. If ad

ustable lever stops are

desired, order 4074ECK Envelope Assembl

, which contains

two ad

ustable lever stop brackets, one brass insert, one

mountin

screw and two lockin

screws with insulated heads.

When installed, the stop brackets limit the movement of the

T874 HEAT and COOL levers.

TO INSTALL:

1. Remove the thermostat cover b

pullin

the bottom

e of the cover upward until it snaps free of the

mountin

slots.

2. Turn to the back of the T874 Thermostat. Locate the

hole for the brass insert in the plastic base below the

LED window.

3. Push the brass insert into the hole with fin

er.

4. Turn to the front of the T874 Thermostat.

5. Place the two stop brackets in position with the tabs in

the slot between the HEAT and COOL levers. See

. 9.

Fig. 9. Range limiting and lever locking methods.

6. Insert the mountin

screw into the two slots in the stop

brackets and attach to the brass insert. Ti

hten the

screw to pull the brass insert into the back of the ther-

mostat.

7. Loosen the mountin

screw enou

h to free the stop

brackets for ad

ustment.

T External temperature readout, T rela

R1, R2 LO and HI speed fan rela

RS Coolin

contactor

Y M Compressor contactor

Table 5. Terminal Designationsa

Standard Terminal

Designation Alternate Designations or

Customer Specials Typical Connection

aOther terminal desi

nations can be used that are not listed on this table. Refer to the hookup drawin

and internal schematic

for exact connections.

bW3 controls the auxiliar

heat like W2, and allows addin

additional sta

es of auxiliar

heat with outdoor thermostats while

maintainin

the proper second sta

e anticipation.

HEAT

LEVER

HOLES FOR INSULATED

LOCKING LEVER SCREWS

COOL

LEVER HOLE WITH

BRASS INSERT

BRACKET

TABS

ADJUSTABLE

LEVER STOP

BRACKETS BRACKET

SLOTS

MOUNTING

SCREW

ADJUSTABLE STOPS

ADJUSTABLE LOCKING LEVERS

NONADJUSTABLE STOPS

WITH LOCKING LEVER SCREWS

75°F (24°C) MAX. HEAT

75°F (24°C) MIN. COOL

NONADJUSTABLE D.O.D. STOPS

72°F (22°C) MAX. HEAT

78°F

(

26°C

)

MIN. COOL M7626

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

11 60-2485—8

8. Move the HEAT and COOL levers to the maximum tem-

perature desired.

9. Slide the stop brackets until one rests a

ainst the HEAT

lever and the other a

ainst the COOL lever.

10. Firml

hten the mountin

screw.

11. If the HEAT and COOL levers are to be locked in place

at a specific temperature, use the two insulated head

screws supplied instead of the two ad

ustable lever stop

brackets.

CAUTION

Equipment Damage Hazard.

not

use standard screws that provide metal-to-

metal contact with the stop brackets. Short circuit and

potential e

uipment dama

e can result.

Mount Thermostat

1. Remove the thermostat cover b

pullin

the bottom

e of the cover awa

from the base until it snaps free

of the cover clip.

NOTE: The cover is hin

ed at the top and must be removed

pullin

up at the bottom.

2. Carefull

remove and discard the pol

rene packin

insert that protects the mercur

switches durin

ship-

ment.

3. If LED indication

(

EM.HT., CHECK, etc.

)

is to be used

with the Q674 Subbase, install the preprinted insert

under the thermostat setpoint scale. To install, push

both thermostat setpoint levers to the far ends of the

thermostat. Use index fin

er to

entl

pull out the plastic

setpoint scale about 1/4 in.

(

6 mm

)

. Position the desired

preprinted insert in the space above the LED li

hts.

Reposition setpoint levers.

4. Turn over the thermostat base and note the sprin

fin-

ers that en

e the subbase contacts. Make sure the

sprin

fin

ers are

not

bent flat, preventin

proper elec-

trical contact with the subbase.

5. Set the heat anticipator indicator

(

)

to the respective

current settin

of each sta

e. See Set The Heat Antici-

pator section.

6. If the thermostat provides optional lockin

cover assem-

, start the Allen lockin

screws in the cover with the

wrench provided. See Fi

. 10.

7. Note the two tabs alon

the top inside ed

e of the ther-

mostat base. The tabs fit into correspondin

slots on top

of the subbase. Mount the thermostat on the subbase.

8. Ali

n the two captive mountin

screws in the thermostat

base with the posts on the subbase. Ti

hten both

screws.

Do not overtighten screws

or dama

e to sub-

base posts can result.

Fig. 10. Installation of locking cover assembly.

SETTINGS

CAUTION

Equipment Damage Hazard.

On s

stems usin

as valve, never appl

umper

across the valve coil terminals, even temporaril

. This

can burn out thermostat heat anticipator

(

)

Set the Heat Anticipator

Move the indicator to match the primar

control current draw.

When usin

a T874 Thermostat with two sta

es of heatin

set each heat anticipator to match its respective primar

control current draw. If

ou cannot find the current ratin

the primar

control, or if further ad

ustment is necessar

, see

NOTE and use the followin

procedure to determine the

current draw of each sta

The current draw of each heatin

sta

e must be measured

with the thermostat removed and power on to the heatin

stem.

1. Connect an ac ammeter of appropriate ran

e between

the heatin

terminals of the subbase:

a. Sta

e 1—between W1 and RH or R;

b. Sta

e 2—between W2 and RH or R

c. Sta

e 3—between W3 and RH or R.

2. Move the s

stem switch to HEAT or AUTO.

3. After one minute, read the ammeter and record the

readin

a. Sta

e 1—__________A;

b. Sta

e 2—__________A;

c. Sta

e 3—__________A.

NOTE: If e

uipment c

cles too fast, set the indicator to a

her current ratin

, but not more than one-half divi-

sion at a time, and recheck the c

cle rate. Most con-

ventional two-sta

e heatin

uipment is desi

ned

to operate at three c

cles per hour per sta

e, and

one-sta

e heatin

uipment at six c

cles per hour,

at 50 percent load conditions. When usin

the T874

Thermostat in heat pump s

stems, set the heat

ALLEN

RETAINING

SCREWS (2)

M956

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—812

anticipator at 140 percent of the actual primar

con-

trol current draw to reduce the c

clin

rate. See Fi

11.

Most heat pump s

stems should c

cle 2-1/2 to 3 times per hour.

4. Han

the upper ed

e of the thermostat cover on top of

the thermostat base and swin

the cover downward

until it en

es with the cover clip.

Fig. 11. Adjustable heat anticipator scales.

Temperature Setting

Move the heatin

and coolin

levers to the desired comfort

positions. See Fi

. 12. On some models with two sta

es of

heatin

or coolin

, the same lever controls both sta

es. The

minimum differential between heatin

and coolin

setpoints is

4°F

(

2°C

)

(

5°F [3°C]

)

on T874W.

If model has optional screws to lock temperature control

levers, loosen these screws before makin

temperature

ustment; ti

hten the screws when levers are set at desired

position.

Fig. 12. Internal view of T874W (three stages of

heating, two stages of cooling).

Subbase Setting

The subbase switchin

positions control the s

stem operation

as described below.

SYSTEM SWITCH

(

see subbase for positions

)

OFF—both the heatin

and coolin

stems are off. If the

fan switch is at the AUTO position, the coolin

fan is

also off.

HEAT—heatin

stem is automaticall

controlled b

the

thermostat. Coolin

stem is off.

AUTO—thermostat automaticall

chan

es between heat-

and coolin

stem operation, dependin

on the

indoor temperature.

COOL—coolin

stem is automaticall

controlled b

the

thermostat. Heatin

stem is off.

EM.HT.—emer

enc

heat rela

is automaticall

controlled

the thermostat. Coolin

stem is off. Compressor is

de-ener

ized.

SUPL.HT.—supplemental heat rela

is ener

ized. Coolin

stem is off. Compressor is de-ener

ized.

WOOD—heatin

stem is operatin

with onl

the wood-

burnin

sta

OIL—heatin

stem is operatin

with onl

the oil-burnin

sta

WOOD/OIL—wood and oil sta

es operate se

uentiall

;

first the WOOD sta

e operates, then the OIL sta

operates if the WOOD sta

e cannot handle the load.

EVAP—controls coolin

stem b

water evaporation; see

uipment instructions for further information.

OVERRIDE—ni

ht setback is disabled.

ON—heatin

stem is controlled b

the thermostat. EM.

HT. or SUPL. HT. rela

is not ener

ized.

FAN SWITCH positions control fan operation as follows:

ON or CONT.—fan operates continuousl

AUTO—fan operates as controlled b

the thermostat in

heat pump s

stems or conventional coolin

mode; fan

operates as controlled b

the plenum switch in conven-

tional heatin

mode.

LO—fan operates constantl

at low speed.

MED—fan operates constantl

at medium speed.

HI—fan operates constantl

at hi

h speed.

To move the subbase switches to the desired control

positions, use thumb and index fin

er to slide the lever. The

lever must stop over desired function indicator position for

proper circuit operation.

Sprin

return momentar

position switchin

feature is

available on selected subbase models. On these models, the

fan switch is positioned to the ri

ht of the s

stem switch. B

movin

the fan switch to the far ri

ht and releasin

it, the ON

position circuit makes. The lever sprin

s back on release. This

position is not marked on the subbase.

Setting the Adjustable Differential

The ad

ustable intersta

e differential feature, on a selected

T874D model onl

, can be identified b

the scale and tension

screw near the heatin

and coolin

mercur

switches. See

. 13. On this model, the number of de

rees between the

makin

of the first and second sta

e mercur

bulbs is

ustable. This feature is especiall

useful if the first sta

controls the comfort temperature, and the second sta

controls the ener

savin

s temperature. Timers, such as the

S6005, for insertion between the first and second sta

control points must be ordered separatel

1.2

.2 .15

.12

.10

1.2

.2 .15

.12

MOVE INDICATOR TO

MATCH CURRENT RATING

OF PRIMARY CONTROL

STAGE ONE

ANTICIPATOR

HEATING

CONTROL

STAGE TWO

ANTICIPATOR

HEATING CONTROL

M5069

STAGE 1

HEATING

STAGE 3

HEATING

STAGE 2

HEATING

LEVER COOLING

LEVER STAGE 1

COOLING

STAGE 2

COOLING

CAPTIVE

MOUNTING

SCREWS (2) M7625

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

13 60-2485—8

Each mark on the scale represents 1°F

(

0.6°C

)

The

differential is factor

set at 2°F

(

1°C

)

the differential can be set

as hi

h as 12°F

(

7°C

)

To set the ad

ustable intersta

differential, loosen the tension screw. See Fi

. 13. Slide the

ustable scale to ali

n with the number of de

rees desired

between sta

es. Use the lower ed

e of the tension screw

bracket as a

uide for ali

nment. In heatin

, slide the lever

wider

apart for a

larger

differential, or

closer

ether for a

smaller

differential. In coolin

, slide the lever

closer

ether

for a

larger

differential, or

wider

apart for a

smaller

differential.

While supportin

the scale with hand, ti

hten the tension screw.

IMPORTANT

Support the scale with hand while tightening tension

screw. See Fig. 13. Failure to do so can result in

twisting and damaging bimetal coil.

Fig. 13. Set adjustable interstage differential.

CAUTION

Equipment Damage Hazard.

When the thermostat is used to control a two-sta

heatin

or coolin

stem, the second sta

e mercur

bulb must never make before the first sta

e bulb, or

severe e

uipment dama

e could result. To prevent

this problem, provide at least 2°F

(

1°C

)

differential

between sta

e-one and sta

e-two make points.

Example: in heatin

, if sta

e-one makes at 70°F

(

21°C

)

sta

e-two should make at 68°F

(

20°C

)

or lower.

Verify the Adjustment

Heating

Start with the heatin

setpoint lever all the wa

to the left.

Slowl

move the lever to the ri

ht,

ust until the first sta

e bulb

makes

(

mercur

rolls to the ri

ht side of the bulb

)

. Note the

settin

on the temperature scale. Slowl

move the lever to the

ht until the second sta

e bulb makes. Note the settin

the temperature scale. The difference between the two

temperatures is the

interstage differential,

which should match

the number set on the scale with the tension screw.

Cooling

Start with the coolin

setpoint lever all the wa

to the ri

ht.

Slowl

move the lever to the left,

ust until the first sta

e bulb

makes

(

mercur

rolls to the left side of the bulb

)

. Note the

settin

on the temperature scale. Slowl

move the lever to the

left until the second sta

e bulb makes. Note the settin

on the

temperature scale. The difference between the two

temperatures is the

interstage differential,

which should match

the number set on the scale with the tension screw.

CHECKOUT

Heating

Move the s

stem switch on the Q674 Subbase to HEAT or

AUTO. Move the heat lever on the T874 about 10°F

(

6°C

)

above room temperature. See Fi

. 12. Heatin

stem should

start and the fan should run after a short dela

. Move the heat

lever about 10°F

(

6°C

)

below room temperature. The heatin

uipment should shut off, and the fan should run for a short

time, then shut off.

In heat pump applications, sometimes time dela

s are

involved before the compressor and auxiliar

heat are

activated. This is due to a minimum-off timer, which prevents

the compressor from restartin

for five minutes from when the

thermostat last turned off the compressor, or from when the

stem first received power.

Cooling

CAUTION

Equipment Damage Hazard.

Do not operate coolin

if outdoor temperature is below

50°F

(

10°C

)

. Refer to manufacturer recommendations.

TENSION

SCREW

ALIGN LOWER

EDGE WITH

SCALE

NOTCH

10°F

SCALE

SLIDE LEVER

WIDER APART

FOR LARGER

DIFFERENTIAL

HEATING

TENSION

SCREW

ALIGN LOWER

EDGE WITH

SCALE

NOTCH

4°F

SCALE

SLIDE LEVER

CLOSER TOGETHER

FOR LARGER

DIFFERENTIAL

COOLING

1 EACH MARK ON THE SCALE REPRESENTS 1°F (0.6°C). M937

1.2

1.5

50 60 70 80

HEAT

TENSION

SCREW

HEATING SET-

POINT LEVER

FIRST

STAGE

SWITCH

SECOND STAGE

(ADJUSTABLE)

SWITCH

SCALE

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—814

Move the s

stem switch on the Q674 Subbase to COOL or

AUTO. Move the cool settin

lever on the T874 Multista

Thermostat about 10°F

(

6°C

)

below room temperature. See

. 12. The coolin

uipment and fan should start. If the

stem has two sta

es of coolin

, both sta

es should start.

Move the cool lever about 10°F

(

6°C

)

above room

temperature. The coolin

uipment and fan should stop.

Fan

Move the s

stem switch to COOL, OFF, or AUTO. If

necessar

, position both temperature settin

levers so that the

heatin

and coolin

uipment are off. Move the fan switch to

ON or CONT. The fan should run continuousl

. When the fan

switch is in AUTO, LO, MED, or HI position, fan operation is

controlled b

the heatin

or coolin

stem.

Outdoor Reset Thermistor (Where

Applicable)

If the s

stem is supplied with a thermistor, it must be used; if

not used, thermostat performance deviates radicall

from

proper operation.

The proper thermistor operation must be verified to ensure the

correct operation of the thermostat. Check thermistor

operations as follows:

1. Disconnect the T wire on the subbase.

2. Use an ohmmeter to measure resistance between the

T wire and the A subbase terminal.

3. Take outdoor temperature at thermistor location and find

the correct thermistor resistance on the Fi

. 14 chart.

4. If the resistance measured in step 2 and the calculated

resistance in step 3 var

more than 15 percent, the

thermistor re

uires replacement. Contact Hone

well or

installin

dealer for replacement packa

ed outdoor ther-

mistor, part no. C815A1005.

Fig. 14. Thermistor resistance chart.

CALIBRATION

Thermostat

T874 Thermostats are accuratel

calibrated at the factor

They do not have provision for field calibration.

Thermometer

The thermometer in

our thermostat has been accuratel

calibrated at the factor

. The thermometer should onl

need

ustment if it has been dropped or shifted due to mishandlin

If the setpoint lever and the thermometer readin

do not

ree, use the followin

procedure:

1. Remove the thermostat cover b

pullin

up from the

bottom ed

e of the cover awa

from the base until it

snaps free of the cover clip.

2. Set the thermostat cover on a table near an accurate

thermometer.

3. Allow ten minutes for cover thermometer to sense area

temperature; compare the readin

s. Be careful not to

touch thermometer or breathe on it.

4. If the readin

s are the same, replace cover and put the

stem into operation.

5. If the readin

s are different, insert a small screwdriver in

the thermometer slot and turn it until the thermometers

have the same readin

. See Fi

. 15.

6. Replace thermostat cover and put the s

stem into oper-

ation.

Fig. 15. Thermometer calibration.

UNDERSTANDING CIRCUITS

To understand wirin

dia

rams, it is important to know what all

the s

mbols mean and how to trace the path of the circuits

from the transformer. See Fi

. 16 throu

h 25.

Circuit descriptions and terminolo

are defined as follows:

For standard heatin

-coolin

circuits:

Auto chan

eover—refers to the presence of an AUTO

position in the s

stem switchin

(

EX: Q674E with OFF-

HEAT-AUTO-COOL switchin

. The thermostat auto-

maticall

chan

es between heat and cool modes as

indoor temperature chan

es.

Manual chan

eover—re

uires a s

stem switch movement

to chan

e mode

(

EX: Q674B with HEAT-OFF-COOL

switchin

. T874D Multista

e Thermostats with 2 heat

or 2 cool switches are shown on most standard circuits.

Most standard or TRADELINE® subbases

(

Q674A-E,G

)

can be used with T874A-F standard or TRADELINE

THERMISTOR RESISTANCE (ohms)

C815A THERMISTOR RESISTANCE

R = 400 ohms ± 10% AT 77°F (25°C)

4600

4400

4200

4000

3800

3600

3400

3200

3000

2800

2600

2400

2200

2000

1800

1600

1400

1200

1000

800

600

400

200

0-20 0 20 40 60 80 100 120 140

TEMPERATURE OF THERMISTOR

(

°F

)

M1590A

M5070

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

15 60-2485—8

thermostats. The schematics can be field-modified as

uired

(

EX: if T874C is bein

used, eliminate second

sta

e of heat

)

For heat pump circuits:

Cool chan

eover valve—operates on coolin

. The revers-

valve or rela

is activated either b

movin

the s

tem switch to COOL

(

manual chan

eover

)

or b

mercur

switch that makes on a temperature rise

(

auto

chan

eover

)

Heat chan

eover valve—operates on heatin

. The revers-

valve or rela

is activated either b

movin

the s

tem switch to HEAT

(

manual chan

eover

)

or b

mercur

switch that makes on a temperature fall

(

auto

chan

eover

)

stem monitor rela

—optional e

uipment on some heat

pumps includes an R4222P1065 or e

uivalent. This

stem monitor rela

detects a malfunction in the com-

pressor and indicates the malfunction b

activatin

the

EMERGENCY HEAT LED on the Q674 Switchin

Sub-

base. The s

stem monitor rela

is usuall

wired into the

L terminal on the Q674.

Each mercur

switch is identified b

function:

H1—Sta

e 1 Heatin

H2—Sta

e 2 Heatin

H3—Sta

e 3 Heatin

C1—Sta

e 1 Coolin

C2—Sta

e 2 Coolin

C3—Sta

e 3 Coolin

C/O—Chan

eover

(

heat pumps

)

Each anticipator is identified and each switch affected is

named

(

EX: H1 anticipator, C1 anticipator

)

All T874 Multista

e Thermostats use mercur

switches. Each

schematic indicates switch operation b

bein

drawn in the

open position with an arrow indicatin

operation with a

temperature RISE or FALL.

One circuit has been selected that is t

pical of various models

used with heat pumps. This circuit has been traced to

illustrate the functions performed b

these control s

stems.

Tracing Method:

1. Alwa

s be

in at the s

stem transformer or R terminal.

You ma

want to draw the switch contacts in each

switch position to aid in tracin

. Colored pencils are

helpful when onl

one cop

of the circuit is available.

See Fi

. 16 for a description of the hookup s

mbols and

. 17 throu

h 25 for t

pical hookups.

2. Completel

trace onl

one circuit at a time

(

for example:

heat or cool

)

3. Connections are indicated b

small dots at the point of

intersection. If there is no dot, there is no connection.

4. The left portion of the circuit

(

the thermostat

)

contains

the mercur

switches. The heat switches make on a

temperature fall, and the cool switches make on a tem-

perature rise. Fixed anticipation is represented b

a zi

line and ad

ustable anticipation is a zi

with an

arrow. The resistance of the fixed anticipator is so lar

it limits current so that a s

stem rela

cannot be pulled

in from a circuit path

oin

throu

h the fixed anticipator.

The rela

can be pulled in throu

h an ad

ustable antici-

pator because its resistance is

enerall

0 to 5 ohms.

5. The center portion

(

the subbase

)

contains the switches.

The fan switch is above the s

stem switch. The small

circles on the switch represent the maximum possible

contacts available on the Q674 Subbase. The lar

er cir-

cles represent the switch positions available on this par-

ticular Q674, with the solid circle representin

where it

is actuall

switched on the dia

ram.

NOTE: Solid circles are not interconnected electricall

At the ri

ht, the rela

s and contactors are shown, attached to

the proper terminals. The terminals are represented b

lar

circles with terminal desi

nations in capital letters. See Table

3 for the meanin

of each lettered terminal.

Sometimes power for a fixed anticipator is brou

ht throu

h an

off s

stem rela

like the chan

eover rela

shown in Fi

. 20.

This current is kept low b

the hi

h resistance of the fixed

anticipator so that rela

does not pull in.

Fig. 16. Key to hookup symbols.

M5848

KEY TO HOOKUP SYMBOLS

TRANSFORMER

(24 VAC SECONDARY)

RELAY/CONTACTOR CONTACTS

LED

RELAY OR CONTACTOR COIL

MERCURY SWITCH

FIXED ANTICIPATOR

HIGH RESISTANCE

(TYPICALLY 5 KILOHMS)

ADJUSTABLE ANTICIPATOR

LOW RESISTANCE

(TYPICALLY 0 TO 5 OHMS)

TERMINAL

ODT

OUTDOOR THERMOSTAT

EHR

EMERGENCY HEAT RELAY

RTD

TIME DELAY RELAY

DEFROST RELAY

CHP

PRESSURE SWITCH

LACO

LOW AMBIENT CUTOFF

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—816

Fig. 17. Internal schematic and typical hookup of a T874R Thermostat and Q674L Subbase in a heat pump application.

The thermostat provides two-stage heating and one-stage cooling manual changeover operates on cooling.

M5072A

(HOT) L1 L2

LACO CHP

RODT 1

RTD 1 EHR 1 RTD 2

ODT 2

EHR 2 RTD 3

SYSTEM

MONITOR

FAN RELAY

COMPRESSOR

CONTACTOR

COOL CHANGEOVER

VALVE

EM. HT.

RELAY

RTD 1

AUX. HT.

LED

(GREEN)

EM. HT.

LED (RED)

FAN SWITCH

AUTO

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

FALL

H1/C1

ANTICIPATOR

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

AUXILIARY HEAT LED AVAILABLE ON SOME MODELS.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

17 60-2485—8

Fig. 18. Tracing the changeover relay circuit.

Fig. 19. Tracing the heat 1 and anticipation circuit.

M5840

(HOT)

LACO CHP

ODT 1

RTD 1 EHR 1 RTD 2

ODT 2

EHR 2 RTD 3

SYSTEM

MONITOR

FAN RELAY

COMPRESSOR

CONTACTOR

CHANGEOVER

VALVE

EM. HT.

RELAY

RTD 1

AUX. HT.

LED

(GREEN)

EM. HT.

LED (RED)

FAN SWITCH

AUTO

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

FALL

H1/C1

ANTICIPATOR

1POWER SUPPLY. PROVIDE

DISCONNECT MEANS AND

OVERLOAD PROTECTION

AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

M5841

(HOT)

LACO CHP

RODT 1

RTD 1 EHR 1 RTD 2

ODT 2

EHR 2 RTD 3

SYSTEM

MONITOR

FAN RELAY

COMPRESSOR

CONTACTOR

CHANGEOVER

VALVE

EM. HT.

RELAY

RTD 1

AUX. HT.

LED

(GREEN)

EM. HT.

LED (RED)

FAN SWITCH

AUTO

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

FALL

H1/ C1

ANTICIPATOR

1POWER SUPPLY. PROVIDE

DISCONNECT MEANS AND

OVERLOAD PROTECTION

AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—818

Fig. 20. Tracing the heat 1 anticipation circuit.

Fig. 21. Tracing the heat 2, anticipation and AUX. HT. LED circuit.

M5842

(HOT)

LACO CHP

RODT 1

RTD 1 EHR 1 RTD 2

ODT 2

EHR 2 RTD 3

SYSTEM

MONITOR

FAN RELAY

COMPRESSOR

CONTACTOR

CHANGEOVER

VALVE

EM. HT.

RELAY

RTD 1

AUX. HT.

LED

(GREEN)

EM. HT.

LED (RED)

FAN SWITCH

AUTO

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

FALL

H1/ C1

ANTICIPATOR

1POWER SUPPLY. PROVIDE

DISCONNECT MEANS AND

OVERLOAD PROTECTION

AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

M5843

(HOT)

L2 1

LACO CHP

RODT 1

RTD 1 EHR 1 RTD 2

ODT 2

EHR 2 RTD 3

SYSTEM

MONITOR

FAN RELAY

COMPRESSOR

CONTACTOR

CHANGEOVER

VALVE

EM. HT.

RELAY

RTD 1

AUX. HT.

LED

(GREEN)

EM. HT.

LED (RED)

FAN SWITCH

AUTO

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

FALL

H1/C1

ANTICIPATOR

1POWER SUPPLY. PROVIDE

DISCONNECT MEANS AND

OVERLOAD PROTECTION

AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

19 60-2485—8

Fig. 22. Tracing the emergency heat and EM. HT. LED circuit.

Fig. 23. Tracing the cooling circuit.

M5844

(HOT)

LACO CHP

RODT 1

RTD 1 EHR 1 RTD 2

ODT 2

EHR 2 RTD 3

SYSTEM

MONITOR

FAN RELAY

COMPRESSOR

CONTACTOR

CHANGEOVER

VALVE

EM. HT.

RELAY

RTD 1

AUX. HT.

LED

(GREEN)

EM. HT.

LED (RED)

FAN SWITCH

AUTO

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

FALL

H1/C1

ANTICIPATOR

1POWER SUPPLY. PROVIDE

DISCONNECT MEANS AND

OVERLOAD PROTECTION

AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

M5845

(HOT)

LACO CHP

ODT 1

RTD 1 EHR 1 RTD 2

ODT 2

EHR 2 RTD 3

SYSTEM

MONITOR

FAN RELAY

COMPRESSOR

CONTACTOR

CHANGEOVER

VALVE

EM. HT.

RELAY

AUX. HT.

LED

(GREEN)

EM. HT.

LED (RED)

FAN SWITCH

AUTO

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

FALL

H1/C1

ANTICIPATOR

1POWER SUPPLY. PROVIDE

DISCONNECT MEANS AND

OVERLOAD PROTECTION

AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

RTD 1

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—820

Fig. 24. Tracing the auto fan circuit.

Fig. 25. Tracing the fan on circuit.

M5846

(HOT)

LACO CHP

RODT 1

RTD 1 EHR 1 RTD 2

ODT 2

EHR 2 RTD 3

SYSTEM

MONITOR

FAN RELAY

COMPRESSOR

CONTACTOR

CHANGEOVER

VALVE

EM. HT.

RELAY

RTD 1

AUX. HT.

LED

(GREEN)

EM. HT.

LED (RED)

FAN SWITCH

AUTO

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

FALL

H1/C1

ANTICIPATOR

1POWER SUPPLY. PROVIDE

DISCONNECT MEANS AND

OVERLOAD PROTECTION

AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

M5847

(HOT)

LACO CHP

RODT 1

RTD 1 EHR 1 RTD 2

ODT 2

EHR 2 RTD 3

SYSTEM

MONITOR

FAN RELAY

COMPRESSOR

CONTACTOR

CHANGEOVER

VALVE

EM. HT.

RELAY

RTD 1

AUX. HT.

LED

(GREEN)

EM. HT.

LED (RED)

FAN SWITCH

AUTO

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

FALL

H1/C1

ANTICIPATOR

1POWER SUPPLY. PROVIDE

DISCONNECT MEANS AND

OVERLOAD PROTECTION

AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

21 60-2485—8

OPERATION

Heat Anticipation/Cool Anticipation

When controllin

a heatin

unit with a thermostat, the

temperature does not remain exactl

at the thermostat

setpoint, but varies within a certain temperature ran

e. Heat

anticipation is added to the thermostat to reduce this ran

The anticipator is a small resistive heater in the thermostat

that heats when the s

stem is on

(

heat mode

)

or off

(

cool

mode

)

. The heat produced b

the anticipator raises the

internal bimetal temperature sli

htl

faster than the

surroundin

room temperature. The thermostat

anticipates

the need to shut off the heatin

stem sooner than it would if

affected b

room temperature onl

There are two t

pes of heat anticipation, ad

ustable and fixed.

ustable anticipation is also called

current anticipation

. See

. 26. The heater is in series with the mercur

switch and

heatin

primar

. The pointer is ad

usted to match the current

draw of the primar

control, and the correct amount of heat is

added for proper c

cle rates.

Fig. 26. Adjustable anticipation heater in series with load.

Fixed anticipation is also called

voltage anticipation

. See

. 27. The heater is in parallel with the primar

control and is

not affected b

the current draw of the primar

. It establishes

the proper c

cle rate for an

application.

Fig. 27. Fixed anticipation heater in parallel with load.

Heat anticipators add heat durin

the call for heat. Coolin

anticipators are activated while the air conditioner is off. See

. 28. This heater makes the thermostat think it is warmer than

it reall

is, and brin

s it on sooner than the bimetal alone would.

Fig. 28. Internal cooling anticipation schematic.

Interstage Differential

The mercur

switch of each sta

e of heat makes at a sli

htl

different temperature; that is, the mercur

makes the contacts

of the first sta

e bulb at one temperature, and the second

sta

e bulb at another temperature. The difference between

these two temperatures is the

interstage differential

Intersta

e differential is the difference between the two make

points when the bulbs are controlled b

the heatin

of the

bimetal and the action of the heat anticipator. The intersta

differential is 1.9°F

(

1°C

)

between the sta

es of heatin

or the

sta

es of coolin

for most models.

Mechanical differential is the difference between the make

and break points of each switch. The mechanical differential

for the T874 is 1°F

(

0.6°C

)

between the sta

es of heatin

between the sta

es of coolin

for most models.

Droop

The addition of anticipator heat to the bimetal causes a control

factor called

droop

As the weather

rows colder, the heatin

appliance must

operate lon

er and more fre

uentl

. More heat must be added

to the bimetal. The bimetal now thinks it is warmer than it

reall

is, and actual room temperature is controlled at a lower

temperature than the setpoint indicates. At 100 percent heat

load, this droop can be si

nificant.

The C815A Outdoor Reset Thermistor is used in heat pump

stems to minimize droop. Without some method of

counterin

this situation, the occupant could notice the

temperature offset.

Outdoor Reset

Some T874/Q674 models are intended for use with the

C815A Outdoor Thermistor. The outdoor thermistor provides

nificantl

improved thermostat performance when

compared to conventional multista

e thermostats. The C815A

is usuall

located in the heat pump condensin

unit outdoors.

FALL

(HOT) L2

M5823

STAGE 1 HEAT RELAY

H1 ANTICIPATOR

FALL

(HOT) L2

M5824

STAGE 1

HEAT RELAY

H1 ANTICIPATOR

RISE

(HOT) L2

M5825

STAGE 1

COOL RELAY

C1 ANTICIPATOR

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—822

CAUTION

Equipment Damage Hazard.

Due to calibration techni

ues used for T874

Thermostats with outdoor reset, the C815A Thermistor

must be wired into the s

stem at all times. Failure to

do so will result in serious de

radation of performance.

Service and Replacement of C815A Outdoor

Thermistor

To check and verif

thermistor operation, perform the

followin

steps:

1. Disconnect wire from T terminal on subbase.

2. Measure resistance with ohmmeter across the T sub-

base wire and X subbase terminal.

3. Take outdoor temperature measurement at thermistor

location and find correct thermistor resistance on the

chart in Fi

. 29.

4. Compare resistance on the chart with measured resis-

tance. Replace C815A if resistance varies more than 15

percent. Contact installin

dealer for packa

ed replace-

ment outdoor thermistor.

Fig. 29. Thermistor resistance chart.

Features

Two of the features of the T874/Q674 include LED indicators

and restricted setpoint.

LED Indicators

The li

ht-emittin

diodes

(

LED

)

indicators on the subbase

ht on command when somethin

specific happens in the

stem. See Fi

. 30.

Up to four different LEDs are available. The thermostat has a

clear lens window for viewin

each LED. On TRADELINE

models, a small insert is used so the LED function desired can

be selected.

This must be done during installation.

A blank insert is factor

-installed in some T874 models. To

remove it, push both temperature settin

levers to the far ends

of the thermostat. Use index fin

ernail to

entl

pull out the

scaleplate a fraction of an inch. Turn thermostat upside-down,

and the blank insert falls out.

A strip of four inserts is included with TRADELINE T874. Drop

a strip into the recessed area behind the scaleplate so

selected LEDs show. Make sure insert is completel

seated in

recessed area. Let scaleplate pop back; then set levers to

desired position.

•FILTER LED li

hts when the filter is clo

ed and needs

replacement.

•CHECK LED li

hts when somethin

needs to be checked

or done to maintain efficient operation of s

stem. See

heatin

stem instructions for CHECK LED meanin

•EM. HT. LED li

hts when the emer

enc

heat is operatin

•SUPL. HT. LED li

hts when the supplemental heat is

operatin

•LOCKOUT LED li

hts when the s

stem is shut down and

needs maintenance.

•AUXILIARY HEAT LED li

hts when the auxiliar

heat is

operatin

•SERVICE or MALFUNCTION LED can have several

meanin

s. Consult heatin

stem instructions.

LEDs cannot be replaced or added in the field.

Fig. 30. T874/Q674 LED location.

Restricted Setpoint (DoD)

The Department of Defense

(

DoD

)

models are e

uipped with

a restricted setpoint feature for fuel efficienc

Fixed stops are factor

-set so setpoint levers cannot be set

above 72°F

(

22°C

)

on heatin

, or below 78°F

(

26°C

)

on coolin

Applications

The T874/Q674 can be applied to standard residential

stems for automatic or manual chan

eover, to commercial

rooftop applications, or to heat pump applications.

Changeover on Standard Residential

Systems

In a standard residential heatin

-coolin

circuit, chan

eover

between heatin

and coolin

can be done either automaticall

or manuall

Automatic chan

eover is done b

an AUTO position on the

subbase s

stem switch. See Fi

. 31. When the switch is in the

AUTO position, the thermostat automaticall

chan

es between

heat and cool modes, dependin

on the indoor temperature.

THERMISTOR RESISTANCE (ohms)

C815A THERMISTOR RESISTANCE

R = 400 ohms ± 10% AT 77°F (25°C)

4600

4400

4200

4000

3800

3600

3400

3200

3000

2800

2600

2400

2200

2000

1800

1600

1400

1200

1000

800

600

400

200

0-20 0 20 40 60 80 100 120 140

TEMPERATURE OF THERMISTOR (°F) M1590A

80 50 60 70 80 COOL

EM.

HEAT FILTER SERV. AUX

HEAT

M5830

LEDS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

23 60-2485—8

Fig. 31. System switching for automatic changeover.

Automatic chan

eover is fre

uentl

used in areas where there

are lar

e temperature differences in 24 hours. Some uses for

the automatic chan

eover feature are in the southern states

(

cool in the mornin

and hot in the afternoon

)

and in

commercial applications.

Manual chan

eover re

uires a s

stem switch movement to

chan

e the mode. See Fi

. 32. Most manual chan

eover

switches consist of HEAT-OFF-COOL choices. For heatin

switch to HEAT. For coolin

, switch to COOL. It is not automatic.

Manual chan

eover is often used in areas where the

temperature is relativel

stable between da

and ni

ht.

Fig. 32. System switching for manual changeover.

Commercial Rooftop Application

The T874 can be used as part of a commercial rooftop

application to run mechanical coolin

An economizer is often used as part of a rooftop application to

save on air conditionin

. See Fi

. 33.

Fig. 33. Typical commercial rooftop economizer

application.

Enthalpy

is the temperature and humidit

of the air. A more

accurate anal

sis of the suitabilit

for free coolin

can be

made b

monitorin

the enthalp

When enthalp

is low enou

h, the thermostat and a sensor

tell the economizer damper to open to let in cool air from the

outside. When enthalp

is hi

h, the thermostat and sensor tell

the damper to close. No more outside air comes in, so the air

conditioner is used instead.

Heat Pump Application

A heat pump s

stem operates much like an air conditioner.

However, the heat pump is capable of movin

heat in two

directions; from inside the home to outdoors for coolin

, or

from outdoors to inside for heatin

The heat pump can be controlled b

separate rela

/contactor

components, which are ener

ized or de-ener

ized b

the T874.

Chan

eover between heatin

and coolin

for heat pump

circuits can be accomplished either manuall

or automaticall

Manual chan

eover control re

uires a s

stem switch

movement to chan

e the mode. The reversin

valve is

activated b

movin

the s

stem switch to COOL for coolin

to HEAT for heatin

operation.

Automatic chan

eover is accomplished b

one of the mercur

bulb switches in the thermostat. On a s

stem with automatic

chan

eover on coolin

, the chan

eover valve is ener

ized b

a mercur

switch that makes on a temperature rise. On

heatin

, the chan

eover valve is ener

ized b

a mercur

switch that makes on a temperature fall.

A description of the methods used to control heat pumps

follows.

Space Temperature Sensing Low Voltage

Controls

Control s

stems for heat pumps usuall

utilize low volta

control circuits. The variet

of control functions re

uired and

the relative complexit

uire a versatile and economical

method of control. There are several interlocks and indication

functions that would be more difficult and expensive to wire in

line volta

e circuits. Low volta

e controls have the precision

and flexibilit

needed.

The thermostat used is a low volta

e device that has

ood

temperature sensitivit

and several manual and automatic

switchin

capabilities.

Two-Stage Thermostat

In most installations, the heat pump itself re

uires auxiliar

heat, usuall

in the form of electric strip heaters, to carr

the

buildin

heatin

load at desi

n conditions. Since the heat

pump is usuall

more efficient, the control strate

is to run

the heat pump

whenever possible

and the auxiliar

heat

only

when necessary—

durin

ver

cold weather or if the heat

pump fails. Usuall

the auxiliar

heat is used onl

below the

balance point

(

temperature at which the heat pump cannot

handle heatin

load b

itself

)

A two-sta

e thermostat makes this possible. The two sta

make

sequentially

as the temperature drops. There is a

ree or two between sta

es so that the second sta

(

the

OFF EM. HT. HEAT AUTO COOL

M5828

OFF EM. HT. HEAT COOL

M5829

M5827A

H205 OR H705

ENTHALPY

CONTROL

RETURN

AIR

DISCHARGE AIR SENSOR

DOWNSTREAM FROM THE

EVAPORATOR COIL

OUTDOOR

AIR

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—824

one controllin

the auxiliar

heat

)

makes onl

when the heat

pump alone cannot handle the load. That is how the strate

of usin

the most economical heat first is implemented.

Cycling Rate

Normall

, thermostat anticipation is set to c

cle a fossil fuel

furnace about five or six times an hour

(

at 50 percent load

)

This provides a reasonable balance between comfort, stabilit

and econom

A heat pump, bein

a mechanical refri

eration s

stem, should

be c

cled at a rate of 2-1/2 to 3 times an hour. With a T874,

this is accomplished b

settin

the anticipator at the total

current draw of the controlled device

(

the contactor and

possibl

the chan

eover rela

or valve

)

. Most likel

, the

compressor operates from the first sta

e of the thermostat.

The second sta

e normall

controls the auxiliar

heaters. This

heat anticipator can be set for the current draw of the electric

heat primar

, and produces

ood control.

Voltage Anticipation

Althou

h not a specific re

uirement for heat pumps, several

models of the T874 have volta

e heat anticipation instead of

current anticipation.

With volta

e anticipation, the amount of heat added to the

thermostat is constant no matter which load is connected to it.

The anticipator realizes a constant volta

e and produces a

constant amount of heat durin

the ON c

cle. This allows the

clin

rate to be

designed into

the thermostat. The heat

pump manufacturer is assured of correct performance

independent of later thermostat ad

ustments.

Outdoor Reset

Outdoor reset, which a C815A Outdoor Thermistor makes

possible, is sometimes applied in heat pump s

stems to help

minimize the effect of the differential between sta

es. It takes

2°F

(

1.1°C

)

chan

e in temperature to brin

on the second

sta

e and full heatin

. Added to a certain amount of droop

under hi

h loads, there can be a lar

e offset between the

setpoint and room temperature.

Without some method to counteract this situation, the

temperature offset from the setpoint could be as much as 6°F

(

3.3°C

)

under hi

h load conditions. It is not likel

that the

occupants accept this variation without makin

fre

uent

thermostat settin

chan

es.

Outdoor reset has the effect of raisin

the setpoint at cold

outdoor temperatures. Then, even with a few de

rees droop,

the space temperature sta

s near the desired settin

This is done b

calibratin

the thermostat hi

h b

5°F

(

3°C

)

—

the amount of expected offset. This offset compensates for

differential and droop at hi

h load factors so the thermostat

switches at the setpoint. At warm temperatures, heat is added

to the thermostat to compensate for this offset; at cold

temperatures, the extra heat is automaticall

removed. The

effect is the same as raisin

the setpoint as the outdoor

temperature

oes down.

This is particularl

important on the 3-sta

e T874. The

additional sta

e means that more droop is introduced when

the s

stem is in operation. That is the reason the TRADELINE

T874W is sold in a packa

e with the outdoor sensor and the

correct subbase.

Outdoor Reset—How it Works

The heater in the thermostat is connected in series with a

thermistor sensor that measures outdoor temperature. See

. 34. In warm weather, the thermistor has ver

low

resistance, permittin

a lar

e current flow in the heater, which

enerates a relativel

lar

e amount of heat in the thermostat.

In cold weather, the outdoor sensor has hi

h resistance,

which results in low current flow and little or no heat bein

added to the thermostat. This raises the control point,

overcomin

the effects of droop and intersta

e differential.

Fig. 34. Location of thermistor.

Changeover

Chan

eover between heatin

and cooin

can be

accomplished either

automatically

manually

, dependin

the application. Chan

eover can occur in heatin

or coolin

The chan

eover valve is ener

ized as lon

as the subbase

function switch is in the appropriate position when

manual

chan

eover is used. If a s

stem manuall

chan

es over on

coolin

, the valve ener

izes whenever the subbase switch is

in the coolin

mode.

One of the mercur

bulb switches is used for control when the

thermostat has

automatic

chan

eover. When the

automatic

chan

eover is in coolin

, the chan

eover valve is ener

ized

when the first sta

e coolin

switch makes. The second sta

switch turns on the compressor.

It is more common with new e

uipment to find that

chan

eover occurs with coolin

; that is, the chan

eover valve

is ener

ized to produce coolin

Whether

automatic

manual

chan

eover is used and

whether the reversin

valve is ener

ized with coolin

or with

heatin

, a heat pump s

stem can be controlled b

the

appropriate T874 Multista

e Thermostat.

(HOT)

RESET

HEATER

C815A

OUTDOOR

THERMISTOR

SENSOR

M5826

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

25 60-2485—8

Low Temperature Lockouts

Some manufacturers of heat pumps have previousl

controlled

their units so the compressor was locked out below a specified

outdoor temperature. This was done because of the stress

placed on the compressor b

the ver

cold temperatures, and

the fact that efficienc

drops off at low temperatures.

Other manufacturers sa

that althou

h efficienc

is low at cold

temperatures, the problem of startin

the cold compressor is

the most critical point. It is more important to keep the

compressor runnin

than to shut it off and tr

to restart it when

the temperature warms up to +10°F

(

-12°C

)

. Also the

crankcase heater, which can run onl

when the compressor is

off, compensates for the lower compressor efficienc

. So, it is

uitable to let the heat pump run even with a coefficient of

performance

(

COP

)

sli

htl

less than one, rather than to turn it

off and have to run the crankcase heater.

NOTE: To determine the COP of a heat pump, use the fol-

lowin

formula:

COP = Btu Out/Btu we pa

for or Btuh Capacit

Unit Watta

e x 3.413 Btu/Watt

Another factor favorin

this control strate

is that newer heat

pump desi

ns maintain a level of efficienc

even at outdoor

temperatures well below zero. Some brands do not reach

1.0 COP until -25°F

(

-32°C

)

Virtuall

all manufacturers now let the heat pump run

continuousl

rather than lock it out at cold temperatures.

Heat Pumps with Dual Compressors

Sta

residential sized heat pumps is a re

uirement that

developed from the need to make heat pumps as efficient as

possible. One of the methods used to improve overall

seasonal efficienc

is to reduce the amount of time the

machine is operatin

in a transitional mode. Transitional mode

is startin

and stoppin

in addition to recoverin

from defrost.

Under li

ht loads, when the heat pump is c

clin

on and off,

this can be a si

nificant amount of time and can result in a

nificant efficienc

reduction. Capacit

control is one wa

reduce the c

clin

rate and improve the efficienc

Additional capacit

control methods used on other

refri

eration s

stems

(

unloadin

, multiple compressors

)

are

not as likel

to be seen on residential heat pumps.

With a sin

le-sta

e heat pump, the compressor is normall

controlled b

the first sta

e and the auxiliar

heat b

the

second sta

e. The T874G, N and R Thermostats are used for

this purpose.

With a two-sta

e compressor, the two thermostat switches

control the individual compressor sta

es. Auxiliar

heat is

controlled alon

with the compressor sta

e-two, b

the

thermostat second sta

e. It comes on with the compressor

h speed if an outdoor thermostat—wired in series with it—

is made. See Fi

. 35.

Fig. 35. Two-stage heat pump with two-stage thermostat.

The outdoor thermostat is set at the balance point with both

heat pump sta

es runnin

. So if the heat pump can control the

heatin

load down to +20°F

(

-7°C

)

, the auxiliar

heat comes

on with the second sta

e of the compressor.

In effect, this control strate

chan

es the heat input of the

second sta

e, dependin

on the amount of heat needed.

Additional sta

es of auxiliar

heat can be added with or

without the control of more outdoor thermostats, See Auxiliar

Heat section.

Another wa

to control a two sta

e heat pump is with a three-

sta

e thermostat. The T874W is desi

ned for this application

as well as others. See Fi

. 36.

The advantage of this system is that no auxiliary heat is used

until there is an actual demand from the controlled space.

Fig. 36. Two-stage heat pump with three-stage

thermostat.

Two speed Heat Pump

One wa

to control capacit

is to use a two-speed

compressor. The compressor runs at low speed for sta

e-one

heatin

and coolin

. The compressor runs at the low speed

instead of c

clin

the heat pump on and off under some li

load conditions.

The hi

h speed is sta

e-two coolin

. The compressor runs on

h speed when loads increase so the low speed can no

lon

er handle the coolin

load. This reduces c

clin

rate and

improves capacit

M5838

THERMOSTAT

HEAT 2 HEAT 1

OUTDOOR

THERMOSTAT

COMP.

STAGE 2

AUXILIARY

HEAT

COMP.

STAGE 1

M5837

COMP.

STAGE 2

THERMOSTAT

HEAT 2 HEAT 1

AUXILIARY

HEAT

HEAT 3

COMP.

STAGE 1

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—826

Defrost Control

In some re

ions, durin

half or more of the heatin

season,

the outdoor coil operates below 32°F

(

0°C

)

Frost or ice builds

up on the outdoor coil of a heat pump similarl

to the frost

buildup in a household refri

erator. Eventuall

, this

accumulation of ice interferes with efficient heat transfer from

the outdoor air to the coil and refri

erant. Defrostin

occasionall

uired to remove this ice, and restore the heat

pump abilit

to absorb heat from the air.

Defrosting

A heat pump defrosts its outdoor coil b

temporaril

switchin

to the coolin

mode, which causes hot

as from the

compressor to be directed to the outdoor coil instead of to the

indoor coil so the heat pump is takin

heat from the home to

warm up the outdoor coil. Defrostin

is the

reatest detriment

to heat pump efficienc

Defrost Control Functions

Besides chan

over to the coolin

mode, defrostin

uires several more control initiated actions that follow.

OUTDOOR FAN

When defrostin

has be

un, it is standard practice to turn off

the outdoor fan to speed up the meltin

process. A separate

defrost rela

is re

uired to control that fan. See Fi

. 37. Other

contacts can be needed on the defrost rela

to power the

chan

eover valve or power part of the auxiliar

heat.

Fig. 37. Outdoor fan with defrost control.

AUXILIARY HEAT DURING DEFROST

Most pump manufacturers brin

on some auxiliar

heat durin

defrost, althou

h this is not a universal practice. Some rel

the second sta

e of the thermostat to call for auxiliar

heat as

needed. Since the heat pump is operatin

in the coolin

mode

to defrost, it is deliverin

cold air to the livin

space. Auxiliar

heat is used to offset this coolin

. It re

uires another normall

open contact on the defrost rela

. See Fi

. 38.

Fig. 38. Auxiliary heat with defrost control.

WHEN TO DEFROST

Timel

defrostin

is an essential component of effective heat

pump operation. Failure to defrost often enou

h permits too

much ice to accumulate on the coil. At the ver

least, this

hurts efficienc

; at worst, it results in compressor dama

Insufficient defrostin

is a condition the heat pump

manufacturer wants ver

much to avoid.

A 50 percent reduction in outdoor airflow is the maximum that

would be tolerated. So the desi

ner of a heat pump would

select a control point that puts the s

stem into defrost when

airflow throu

h the outdoor coil approaches half its normal

level. Restricted airflow causes a

reater load on the

compressor; the outdoor coil runs colder, suction pressure is

lower and the motor runs hotter.

At the other end of the scale, defrostin

too often hurts the

overall ener

efficienc

of the s

stem. Consider that in terms

of heatin

the buildin

, defrostin

is a bi

loss. Not onl

does

the s

stem stop heatin

, but it actuall

moves heat out of the

buildin

. If electric strip heat is used, it is a further waste

because its COP is 1.0 and not the 2.0 or more COP realized

if the heat is provided b

the heat pump.

So, concern for e

quipment safety

ests fairl

fre

uent

defrostin

while

economy of operation

ues for fewer

defrost c

cles. Since the e

uipment manufacturer chooses, the

balance is usuall

tipped in favor of more fre

uent defrostin

avoid the possibilit

of dama

the compressor.

Auxiliary Heat

Except in warm climates, all air-to-air heat pump installations

uire auxiliar

heat capabilit

. Electric resistance heaters

can provide this auxiliar

heat.

The electric heaters

(

sometimes called strip heaters

)

usuall

are supplied in 5 kW units or strips

(

about 17,000 Btu

)

. The

indoor unit of the heat pump is desi

ned to accommodate

various electric heat units so it can be used in variousl

sized

buildin

s in different parts of the countr

Two-Stage Thermostat

The most common heat pump control strate

is for the

thermostat first sta

e to switch the compressor and the

second sta

e to switch the auxiliar

heat. See Fi

. 39.

M5839

COMPRESSOR

MOTOR

CONTACTOR

CONTROLLED BY

DEFROST RELAY OUTDOOR

FAN MOTOR

M5835

THERMOSTAT

HEAT 2 HEAT 1

DEFROST

RELAY

CONTACT

AUXILIARY

HEAT RELAY

(HOT)

TRANSFORMER

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

27 60-2485—8

Fig. 39. Auxiliary heat in two-stage thermostat.

This method keeps the auxiliar

heat off until the heatin

load

is lar

e enou

h to demand 100 percent heat pump operation.

That demand is measured b

the thermostat and is the actual

heat re

uirement of the space. The two-sta

e thermostat

uires about a 2°F

(

1.1°C

)

room temperature drop to brin

on the second sta

Stage or Time Modulated Control

There are two different wa

s to control auxiliar

heat, sta

or time modulated control.

Outdoor thermostats

are used to switch additional increments

of electric heat into the thermostat circuit as the outdoor

temperature

ets lower. All increments of auxiliar

heat are

still controlled b

sta

e-two of the thermostat but onl

if the

outdoor temperature re

uires the additional capacit

. See

. 40.

Fig. 40. Outdoor thermostats for auxiliary heat.

The rationale for this s

stem is that it ver

closel

matches the

stem capacit

to the heatin

load of the buildin

. B

calculatin

the heat loss of a buildin

, the installin

contractor

can pick the theoretical outdoor temperature at which to

permit each additional unit of electric heat to be operated b

the second sta

e of the room thermostat.

The disadvanta

e of this s

stem is that it can re

uire several

outdoor thermostats. Also, since the unit is operatin

most

often at nearl

full capacit

, the thermostat is on lon

er which

results in more droop, with a little more offset from the

thermostat setpoint.

In addition, the capacit

is tied to theoretical load, based on heat

loss calculations. Normall

this is ver

close to the actual load,

but there are times where the second sta

e is switched on too

soon

(

no harm done

)

or too late

(

the buildin

ets cold

)

The T874 Thermostat produces

time modulated

control, which

is the on time of the thermostat chan

durin

each c

cle as

the load chan

es. The on time of the heatin

stem is

directl

proportional to the heatin

load of the buildin

. As an

example of the

ualit

of time modulated control, consider the

pical

as furnace. It can have a capacit

of 100,000 Btu

(

293 kW

)

, which is controlled On-Off. The output is 100,000 Btu

(

293 kW

)

or nothin

. A

ualit

thermostat controls so closel

that

the occupants rarel

detect chan

es in room temperature.

The same is true with 50,000 or 60,000 Btu

(

146.5 or

178.8 kW

)

of heat pump auxiliar

electric heat. The T874 can

provide the same hi

ualit

control.

This scheme also eliminates the need for outdoor thermostats

and thus offers the manufacturer an opportunit

to reduce unit

cost. One disadvanta

e is that a

thermostat jiggler

can be

demandin

more kW of strip heat when chill

The method an

particular manufacturer selects depends on

which ar

uments it finds persuasive and the opinions of its

distributors and dealers.

Three-Stage Thermostat

A definite improvement in

ualit

of control and econom

can

be achieved with a three-sta

e thermostat

(

T874W

)

, which is

especiall

true with heat pumps usin

dual compressors.

Three-sta

e control permits both the heat pump and the

auxiliar

heat to be tied directl

to the demand of the

controlled space. With a two-sta

e compressor, maximum

(

100 percent

)

heat pump operation is re

uired before auxiliar

heat is brou

ht on.

Emergency Heat

Some provision is

enerall

uired to back up the compressor

in the event of a failure durin

the heatin

season. In fact, it is

uite common to find that local buildin

codes or electric utilities

uire that a specified percent of the buildin

heatin

uirements be available from emer

enc

heat—a source

other than the heat pump compressor. Almost universall

, the

source is electric resistance heaters. T

picall

, the re

uirement

is for 70 or 80 percent of the buildin

heatin

needs.

Switching to Emergency Heat

Conventional heat pump control

(

thermostat lo

)

usuall

includes a manual subbase switch to brin

on the emer

enc

heat.

In one control strate

, the

emergency heat

rela

is turned on

the EM.HT. selector switch on the thermostat subbase. The

compressor is prevented from runnin

. The electric heaters

are c

cled as the

normall

would be b

the

second stage

M5836

COMPRESSOR

CONTRACTOR

THERMOSTAT

HEAT 2 HEAT 1

AUXILIARY

HEAT RELAY

CONTROLS

AT 65°F (18°C)

CONTROLS

AT 63°F (17°C)

M5834

COMPRESSOR

CONTACTOR

THERMOSTAT

HEAT 2 HEAT 1

AUXILIARY

HEAT RELAY 1

AUXILIARY

HEAT RELAY 2

AUXILIARY

HEAT RELAY 3

OUTDOOR

THERMOSTATS

20°F

(-7°C)

5°F

(-15°C)

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—828

the thermostat. A set of contacts on the emer

enc

heat rela

is used to b

pass each outdoor thermostat so that all electric

heat is under immediate thermostat sta

e-two control. So the

emer

enc

heat rela

simpl

passes the outdoor

thermostats. See Fi

. 41.

In the

second

method, the emer

enc

heat relay is cycled

directl

the thermostat mercur

bulb. In this hookup, the

rela

is controlled b

the thermostat

first stage

. The

emer

enc

heat rela

ener

izes all of the auxiliar

heat rela

on a call for heat. See Fi

. 42.

So the emer

enc

heat is controlled b

the first sta

e of the

thermostat. The emer

enc

heat rela

ener

izes all of the

electric strip heaters so the heat and the indoor fan come on

ether as soon as the first sta

e calls for heat.

With the first method, the fan remains on

(

bein

controlled b

the first sta

e of the thermostat

)

and the electric heaters c

cle

on and off with the second sta

In either case, a subbase indicator li

ht is turned on whenever

the function switch is in the emer

enc

heat

(

EM.HT.

)

position.

Fig. 41. Emergency heat relay that bypasses

the outdoor thermostats.

Fig. 42. Emergency heat relay that energizes all of the

auxiliary heat relays on a call for heat.

Crankcase Heat

In an

mechanical refri

eration s

stem, refri

erant tends to

rate to the coldest part of the e

uipment and condense

there. In a heat pump, this coldest spot could be the compressor

because it is usuall

outdoors. In addition, the oil in the com-

pressor crankcase is capable of absorbin

a hi

h concentration

of refri

erant. On compressor startup, there are two risks:

(

)

the

uid refri

erant, which is noncompressible, can be drawn into

the c

linder, and

(

)

considerable oil can be entrained in the

refri

erant and swept out of the crankcase throu

h the

chan

eover valve and dispersed in the pipin

and coils.

So the mi

ration of refri

erant to the crankcase is undesirable

because it can interfere with s

stem lubrication and because the

uid refri

erant must be kept from

oin

throu

h the compressor.

Addin

a crankcase heater creates enou

h temperature

differential to prevent this mi

ration because the compressor

is no lon

er the coldest part of the s

stem so refri

erant does

not mi

rate to it.

Compressor Fault Relay

Another ver

simple method of detectin

a compressor failure

has been developed. It uses the volta

e developed across the

capacitor in a permanent split capacitor compressor motor.

The principle involved is that virtuall

all serious problems

reduce the volta

e across the motor capacitor. B

carefull

selectin

the correct coil volta

e, the normall

closed rela

does not pull in unless the proper volta

e builds up across the

capacitor, which brin

s on the SERVICE LED. See Fi

. 43.

Here is how it works:

•On a call for coolin

, the thermostat makes R to Y, the

contactor coil is powered, and the compressor motor turns on.

•At the same time, the indicator li

ht is ener

ized.

•As the motor

ets up to speed—about one second, the

fault rela

sees enou

h volta

e to pull in. Its normall

closed contact opens and the indicator li

oes out.

•An

thin

that prevents the motor from runnin

prevents the

fault rela

from pullin

in.

Fig. 43. Compressor fault relay schematic.

M5833

COMPRESSOR

THERMOSTAT

FUNCTION

SWITCH HEAT 2 HEAT 1

EMERGENCY HEAT

RELAY CONTACT EMERGENCY

HEAT RELAY

AUXILIARY

HEAT RELAY 1

AUXILIARY

HEAT RELAY 2

OUTDOOR

THERMOSTAT

M5832

COMPRESSOR

THERMOSTAT

FUNCTION

SWITCH HEAT 2 HEAT 1

EMERGENCY

HEAT RELAY

CONTACT

24 V

EMERGENCY

HEAT RELAY

AUXILIARY

HEAT RELAY

RISE

(HOT)

M5831

COMPRESSOR MOTOR FAULT RELAY

YRLX

LED

CAP.

RUN

START S

CONTACTOR THERMOSTAT-

SUBBASE

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

29 60-2485—8

CROSS REFERENCE

The followin

section lists the current T874 Trade replace-

ments for T872 and T874 Multista

e Thermostats. It also lists

the Q674 Trade replacements for Q672 and Q674 Subbases.

All thermostats listed carr

the Hone

well lo

o unless

otherwise noted.

When usin

the Cross Reference Charts, refer to the followin

instructions:

1. Locate and identif

the existin

thermostat and subbase

model.

2. Refer to the Model Number column to find the model

that matches the existin

thermostat and subbase.

3. The Description column identifies certain characteristics

of the existin

device.

4. The Trade Replacement column identifies the correct

replacement device.

5. The Remarks column lists an

characteristics or ad

ust-

ments to be made on the Trade replacement model.

6. The Fig. No. column lists the wirin

hookup used for the

specific model number. The wirin

dia

rams follow the

Cross Reference section.

7. Refer to the circuit illustration that corresponds with the

appropriate number. This fi

ure illustrates the internal

electric circuit for the desired model number.

Table 6. T872-T874 Thermostat Cross Reference.

Model Number Description T874 Trade

ReplacementaRemarks

T872A 1-sta

e heat, 1-sta

e cool

A1006 Standard OEM T874A1036

A1014 72-78°F

(

22-26°C

)

stop; lockin

cover; no

thermometer T874A1010 Use T874A1176 for Dept. of

Defense

(

DoD

)

application.

A1022 Heat anticipator set at 0.45A T874A1036

A1030 0.4A heat anticipator settin

T874A1036

A1048 TRADELINE T874A1036

A1055 AAF lo

o; lockin

cover T874A1036

A1063 Climatrol lo

o T874A1036

A1071 Lennox lo

o; 0.5A heat anticipator settin

T874A1036

A1089 Melco lo

o T874A1036

A1097 Westin

house lo

o T874A1036

A1105 Amana lo

o; 1.2A heat anticipator settin

T874A1036

A1113 Trane lo

o T874A1036

A1121 Airtemp

(

Chr

sler

)

o T874A1036

A1139 Sin

er lo

o; no. 02005384 T874A1036

A1147 American Standard lo

o T874A1036

A1154 Carrier lo

o and color; no. HH07AT074 T874A1036

A1162 General Electric lo

o; no. AY28X097 T874A1036

A1170 Sears lo

o; no. 4291441 T874A1036

A1188 Command-Aire lo

o T874A1036

A1196 Sin

er lo

o; Celsius scale; no. 02005521 T874A1036

A1204 Carteret lo

o T874A1036

A1212 General Electric; no. AY28X114; 72-78°F

(

22-26°C

)

stop T874A1010 Use T874A1176 for Dept. of

Defense

(

DoD

)

application.

A1220 Sin

er lo

o; no. 050240-01 T874A1036

A1238 Celsius scale T874A1036

A1246 TRADELINE; lockin

cover and ad

ustable lockin

lever stops T874A1150

A1253 Trane Comfort Corp T874A1036

A1261 TRADELINE; 72-78°F

(

22-26°C

)

stop; lockin

cover; no thermometer; meets DoD specs T874A1176

aWhen replacin

a T872 Thermostat and Q672 Subbase, alwa

s replace both the thermostat and the subbase.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—830

A1279 General Electric lo

o; no. AY28X114A; 75°F stop;

lockin

cover; no thermometer. T874A1010 Use T874A1176 for Dept. of

Defense

(

DoD

)

application.

A1287 General Electric; no. AY28X097A; fan current

shunt for auto fan in heatin

; heat anticipator set at

0.4A.

T874A1036/

Q674B1018 Set thermostat sta

e 1 heat

anticipator for total of fan and sta

1 primar

control current draw.

A1295 Lennox; Celsius scale T874A1036

A1303 Lennox lo

o; no. 64A0601; meets DoD specs T874A1176

A1311 Envirotron special; Celsius scale T874A1010

A1329 Carrier lo

o; Celsius scale; no. HH07AT074C T874A1036

A1337 S

uare D; no. HCD-3; heat anticipator set at 0.2A T874A1036

A1345 TRADELINE; Celsius scale T874A1010

A1352 Heat anticipator set 1.2A T874A1036

A1360 Friedrich lo

o; heat anticipator set at 0.2A T874A1036

A1378 Wesco lo

o; heat anticipator set at 0.8A T874A1036

T872B 1-sta

e heat, 2-sta

e cool

B1005 Standard OEM T874B1019

B1013 0.4A heat anticipator settin

T874B1019

B1021 TRADELINE T874B1019

B1039 Westin

house lo

o T874B1019

B1047 American Standard lo

o T874B1019

B1054 Climatrol lo

o T874B1019

B1062 Carrier lo

o T874B1019

B1070 Trane lo

o T874B1019

B1088 Fedders lo

o T874B1019

B1096 Climatrol lo

o T874B1019

B1104 Carteret lo

o T874B1019

B1112 Sin

er lo

o; no. 050240-03 T874B1019

B1120 Celsius scale T874B1019

B1138 Sin

er lo

o; no. 02005711; lockin

cover and

lever. T874B1019

B1146 Lennox lo

o; no. P-8-8895 T874B1019

B1153 Lennox lo

o; Celsius scale T874B1019

T872C 2-sta

e heat, 1-sta

e cool

C1004 Standard OEM T874C1018

C1012 Heat anticipator set at 0.4A T874C1018

C1020 72-78°F

(

22-26°C

)

stop; lockin

cover; no

thermometer; 42-88°F

(

6-31°C

)

setpoint ran

e. T874C1141 Use T874C1141 for Dept. of

Defense

(

DoD

)

application.

C1038 TRADELINE T874C1018

C1046 American Standard lo

o T874C1018

C1053 Friedrich lo

o T874C1018

C1061 Lennox lo

o; no. P-8-8896 T874C1018

C1079 Westin

house lo

o; sta

e 1 heat anticipator set at

0.75A; sta

e 2 anticipator set at 1.2A T874C1018

C1087 Fast c

cle performance on both heat sta

es;

anticipator ran

e 0.12-0.6A T874C1018 Ad

ust anticipator

faster

for correct

performance.

C1095 Pa

ne lo

o; no. 0.1-0.175 T874C1018

Table 6. T872-T874 Thermostat Cross Reference.

Model Number Description T874 Trade

ReplacementaRemarks

aWhen replacin

a T872 Thermostat and Q672 Subbase, alwa

s replace both the thermostat and the subbase.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

31 60-2485—8

C1103 Amana lo

o; anticipator set at 1.2A T874C1018

C1111 Airtemp

(

Chr

sler

)

o T874C1018

C1129 Da

and Ni

ht lo

o; no. 0.1-0.174 T874C1018

C1137 Fast c

cle performance on both heat sta

es T874C1018 Ad

ust anticipator

faster

for correct

performance.

C1145 Rheem lo

o T874C1018

C1152 Ruud lo

o T874C1018

C1160 Climatrol lo

o T874C1018

C1178 Wesco lo

o T874C1018

C1186 Sears lo

o T874C1018

C1194 First Co. lo

o T874C1018

C1202 Carrier lo

o T874C1018

C1210 Carrier lo

o; Celsius scale T874C1018

C1228 0.4A heat anticipator settin

T874C1018

C1236 Carrier lo

o; no. HH07AT070 T874C1018

C1244 Fraser-Johnson lo

o T874C1018

C1251 Trane lo

o T874C1018

C1269 Fedders lo

o T874C1018

C1277 Climatrol special T874C1018

C1285 Auto

as lo

o T874C1018

C1293 Fedders lo

o T874C1018

C1301 Climatrol lo

o T874C1018

C1319 Command-Aire lo

o T874C1018

C1327 Melco lo

o; lock cover and levers T874C1018

C1335 Sin

er lo

(

Carteret

)

T874C1018

C1343 Sin

er lo

o; no. 050240-04 T874C1018

C1350 Celsius scale T874C1018

C1368 12°F

(

67°C

)

differential between heat 1 and

heat 2 T874C1125

C1376 AAF lo

o; lockin

cover; 72-78°F

(

22-26°C

)

stop T874C1018

C1384 Servel lo

o T874C1018

C1392 TRADELINE; fast c

cle performance on both heat

sta

es. T874C1018 Ad

ust anticipator

faster

for correct

performance.

C1400 72-78°F

(

22-26°C

)

stop; lockin

cover; no

thermometer; meets DoD specs T874C1141

C1418 Solaron lo

o T874C1018

C1426 Lennox lo

o; no. 42C04; four LEDs None

C1434 Carrier lo

o; no. HH07AT070C; Celsius scale T874C1018

C1442 Goettl lo

o T874C1018

C1459 Goettl lo

o; used with Q672N1001, N1019 None

C1467 Lennox lo

o; Celsius scale T874C1018

C1475 Tappan lo

o; no. 080-13708-37 T874C1018

C1483 Fasco lo

o; no. 1230-8161 T874C1018

C1491 Lennox lo

o; no. 64A0501; lockin

cover; no

thermometer; meets DoD specs T874C1141

Table 6. T872-T874 Thermostat Cross Reference.

Model Number Description T874 Trade

ReplacementaRemarks

aWhen replacin

a T872 Thermostat and Q672 Subbase, alwa

s replace both the thermostat and the subbase.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—832

C1509 Fedders lo

o; used with Q672L1102 Y594R1425 Wirin

differences

(

old=new

)

: C=X,

K=E; remove Y-W1

umper.

C1517 Climatrol lo

o; used with Q672L1102 Y594R1425 Wirin

differences

(

old=new

)

: C=X,

K=E; remove Y-W1

umper.

C1525 S

uare D lo

o; no. HCD-2 T874C1018

C1533 Airtemp lo

o T874C1018

C1541 Airtemp lo

o; used with Q672L1102 Y594R1425 Wirin

differences

(

old=new

)

: C=X,

K=E; remove Y-W1

umper.

C1566 TRADELINE; Celsius scale T874C1018 Replacement has °F scaleplate.

C1574 Whalen special; used with Q672B1269 None

C1582 Lennox; meets DoD None

C1590 Sin

er; 8°F

(

4.4°C

)

differential between sta

1 and sta

e 2 T874C1125 Replacement has 2°F

(

1° C

)

differential between H1 and H2.

C1608 Sin

er lo

o; no. 02005784 8°F

(

4.4°C

)

differential

between sta

e 1 and sta

e 2 T874C1125 Replacement has 2°F

(

1°C

)

differential between H1 and H2.

C1616 Celsius scale; stop set at 23°C None Add 4074ECK ad

ustable stop.

C1624 Heat Wave lo

o; no. 0360-116 T874C1018

C1632 York lo

o; heat anticipator set at 0.2A T874C1018

C1640 Heat anticipator set at 0.4A T874C1018

C1665 Wesco lo

o; heat anticipator set at 0.8A T874C1018

C1673 Wards lo

o; used with Q672B1285, B1293 Gas s

stems:

T874C1018/

Q674B1034

Electric s

stems:

T874C1018/

Q674B1075

ust anticipator faster for correct

performance.

C1681 Lechauffa

e Urbain lo

o; Celsius scale T874C1018

C1699 Duotherm lo

o; used with Q672E1068 or

Q672F1000 T874C1018 See subbase description for

replacement information.

C1707 Si

ler lo

o; used with Q672N1027 None

C1715 Westin

house lo

o T874C1018

T872D 2-sta

e heat, 2-sta

e cool

D1003 Standard OEM T874D1165

D1011 TRADELINE T874D1165

D1029 Westin

house lo

o T874D1165

D1037 Climatrol lo

o T874D1165

D1045 Lennox lo

o; no. P-8-8897; used with Q672E1191. T874D1165

D1052 York lo

o T874D1165

D1060 Sin

er lo

o; no. 02005385 T874D1165

D1078 Rheem lo

o T874D1165

D1086 Rudd lo

o T874D1165

D1094 York lo

o; lockin

cover T874D1165

D1102 American Standard lo

o T874D1165

D1110 ITT lo

o T874D1165

D1128 Carrier lo

o T874D1165

D1136 No anticipator on sta

e 1 cool; used with

Q672C1029 T874D1165

Table 6. T872-T874 Thermostat Cross Reference.

Model Number Description T874 Trade

ReplacementaRemarks

aWhen replacin

a T872 Thermostat and Q672 Subbase, alwa

s replace both the thermostat and the subbase.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

33 60-2485—8

D1144 Carrier lo

o; no. HH07AT072 T874D1165

D1151 General Electric lo

o; no. AY28X098; 0.4 heat

anticipator settin

T874D1165

D1169 Airtemp

(

Chr

sler

)

o; used with Q672E1118 T874D1165/

Q674E1049 Wirin

differences

(

old=new

)

A=W1; set H1 anticipator to 1.2A.

D1177 Trane lo

o T874D1165

D1185 Dunham-Bush lo

o T874D1165

D1193 Fedders lo

o T874D1165

D1201 Climatrol lo

o T874D1165

D1219 Command-Aire lo

o T874D1165

D1227 Sin

er lo

o; no. 02005522; Celsius scale T874D1165

D1235 Sin

er lo

(

Carteret

)

T874D1165

D1243 Friedrich lo

o T874D1165

D1250 Sin

er lo

o; no. 050240-02 T874D1165

D1268 Airtemp lo

o T874D1165

D1276 Celsius scale T874D1165

D1284 Solaron T874D1165

D1292 Tok

o Carrier lo

o; no. HH07AT072C; Celsius

scale T874D1165

D1300 SUPER TRADELINE T874D1165

D1318 General Electric lo

o; no. AY28X098A; fan current

shunt for auto fan in heatin

.T874D1165/

Q674B1075

D1326 General Electric lo

o; lockin

cover 72-78°F

(

22-26°C

)

stop; fan current shunt for auto fan in

heatin

T874D1165

D1334 Lennox lo

o; Celsius scale T874D1165

D1342 Tappan lo

o; no. 080-13708-32 T874D1165

D1359 Sin

er lo

o; no. 02005740; Celsius scale; 6.6°C

differential between H1 and H2. T874D1165 Onl

2°F

(

1°C

)

differential between

H1 and H2.

D1367 Friedrich lo

o; no. 600-580-23 T874D1165

D1375 Sin

er lo

o; no. 02005713; Celsius scale; controls

2 separate heat/cool circuits; used with

Q674G1017

None

D1383 TRADELINE; Celsius scale T874D1165

D1391 Sin

er lo

o; no. 02005712; controls two separate

heat/cool circuits; used with Q674G1017 None

D1409 12°F

(

7°C

)

differential between H1 and H2 T874D1165

D1417 Fedders lo

o T874D1165

D1425 Climatrol lo

o T874D1165

D1433 Sin

er lo

o; no. 02005785; 8°F

(

4.4°C

)

differential

between H1 and H2 T874D1165

D1441 American Air Filter T874D1165

D1474 Carrier; no. HH07AT072-03; Celsius scale T874D1165

T872E 2-sta

e cool

E1002 Standard OEM T874E1016

E1010 TRADELINE T874E1016

E1028 Westin

house lo

o T874E1016

Table 6. T872-T874 Thermostat Cross Reference.

Model Number Description T874 Trade

ReplacementaRemarks

aWhen replacin

a T872 Thermostat and Q672 Subbase, alwa

s replace both the thermostat and the subbase.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—834

E1036 American Standard lo

o T874E1016

E1044 York lo

o; lockin

cover T874E1016

E1051 ITT lo

o T874E1016

E1069 Climatrol lo

o T874E1016

E1077 Airtemp

(

Chr

sler

)

o T874E1016

E1085 Lennox lo

o T874E1016

E1093 Trane lo

o T874E1016

E1101 Dunham-Bush lo

o T874E1016

E1119 Fedders lo

o T874E1016

E1127 Climatrol lo

o T874E1016

E1135 General Electric lo

o; no. AY28X108 T874E1016

E1143 Lennox lo

o; Celsius scale T874E1016

E1150 Celsius scale T874E1016

E1168 Airtemp lo

o T874E1016

T872F 2-sta

e heat

F1001 Standard OEM T874F1015

F1019 TRADELINE T874F1015

F1027 Lennox lo

o; fast c

cle heat anticipator T874C1018

F1035 Luxaire lo

o; fast c

cle performance on both heat

sta

es. T874C1018 M839 draws 0.72A; set ad

ustable

heat anticipator to settin

of 0.9A

for proper c

cle rate.

F1043 York lo

o; lockin

cover; used with M839. T874C1018

F1050 Raehco lo

o T874F1015

F1068 Fast c

cle performance on both heat sta

es. T874C1018

F1076 Wesco lo

o T874F1015

F1084 Lennox lo

o T874F1015

F1092 Auto Gas lo

o T874F1015

F1100 Celsius scale T874F1015

F1118 Lennox lo

o; Celsius scale T874F1015

F1126 Sta

es 1 and 2 heat electricall

isolated; used with

Q672D1002 None

F1134 S

uare D lo

o; HCD-4 T874F1015

F1159 Wesco lo

o; heat anticipator set at 0.8A T874F1015

F1167 York lo

o T874F1015

F1175 Oneida Heater lo

o; no. 30A0287-01; used with

Q672K1012. T874F1015/

Q674K1026

T872G Heat pump models; 2-sta

e heat,

1-sta

e cool, 1-sta

e chan

eover.

G1000 Fast c

cle performance sta

e 2 heat; fixed

anticipator sta

e 1 heat and cool; chan

eover with

coolin

; used with Q672F1018.

Y594G1252 Wirin

differences

(

old=new

)

W=W2, X1=X.

G1018 Ad

ustable anticipator sta

e 2 heat; fixed

anticipator sta

e 1 heat and cool; chan

eover with

coolin

; used with Q672E1027.

Y594G1393 Wirin

differences

(

old=new

)

Y1=O, Y2=Y.

Table 6. T872-T874 Thermostat Cross Reference.

Model Number Description T874 Trade

ReplacementaRemarks

aWhen replacin

a T872 Thermostat and Q672 Subbase, alwa

s replace both the thermostat and the subbase.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

35 60-2485—8

G1026 Lennox lo

o; fast c

cle performance; sta

e 2 heat;

fixed anticipator sta

e 1 heat and cool;

chan

eover with coolin

; used with Q672E1019,

F1067.

None See subbase description for

replacement information.

G1034 Westin

house lo

o; ad

ustable anticipator sta

e 2

heat; fixed anticipator sta

e 1 heat and cool;

chan

eover with coolin

; used with Q672F1091,

F1141, F1257 or Q672J1013, J1062.

Y594G1252 Wirin

differences

(

old=new

)

W=W2.

G1042 York lo

o; fixed anticipator on all sta

es heat and

cool; chan

eover with coolin

; used with

Q672J1021.

Y594G1567

G1059 TRADELINE; no anticipator sta

e 2 heat; fixed

anticipator sta

e 1 heat and cool; chan

eover with

coolin

; used with Q672J1039 outdoor reset.

Y594G1161 Desi

ned for use on General

Electric heat pumps.

G1067 Lennox lo

o; no. P-8-11222; fast c

cle

performance; sta

e 2 heat; fixed anticipator sta

1 heat and cool; chan

eover with coolin

; used

with Q672E1142, F1083.

See subbase description for

replacement information.

G1075 Carrier lo

o; ad

ustable anticipator sta

e 2 heat;

fixed anticipator sta

e 1 heat and cool;

chan

eover with coolin

; used with Q672J1054,

L1052.

See subbase description for

replacement information.

G1083 Ad

ustable anticipator sta

e 2 heat; fixed

anticipator sta

e 1 heat and cool; chan

eover with

coolin

; includes shunt to b

pass sta

e 2

anticipator with auxiliar

heat rela

s; used with

Q672F1158.

Y594G1252

G1091 Lennox lo

o; same as T872G1026 except meets

DoD specs. See subbase description for

replacement information.

G1109 Tappan lo

o; no. 080-13708-52; ad

ustable

anticipator sta

e 1 heat and cool; chan

eover with

coolin

; used with Q672F1117.

Y594G1252 Wirin

differences

(

old=new

)

: C=X.

G1117 Chan

eover; used with Q672F1125. Y594G1252 Wirin

differences

(

old=new

)

: C=X.

G1125 Lennox lo

o; no. 63A0401; Celsius scale; isolated

auxiliar

heat power circuit; fast c

cle anticipator

sta

e 2 heat.

None

G1133 Rheem lo

o; no. RXMT-B71; ad

ustable

anticipator sta

e 2 heat; fixed anticipator sta

e 1

heat and cool; chan

eover with coolin

; includes

shunt to b

pass sta

e 2 anticipator with auxiliar

heat rela

s; used with Q672F1158, F1232.

Y594G1252

G1141 Ruud lo

o; ad

ustable anticipator sta

e 2 heat;

fixed anticipator sta

e 1 heat and cool;

chan

eover with coolin

; includes shunt to b

pass

sta

e 2 anticipator with auxiliar

heat rela

s; used

with Q672F1158.

Y594G1252

G1158 Carrier lo

o; same as T872G1075. Except DoD

lin

. See subbase description for

replacement information.

G1166 BDP used with Q672F1125. Y594G1252 Wirin

differences

(

old=new

)

: C=X.

G1174 BDP used with Q672F1125. Y594G1252 Wirin

differences

(

old=new

)

: C=X.

G1182 Carrier; no. HH07AT071C; Celsius scale; used

with Q672L1052, J1054. See subbase description for

replacement information.

G1190 Tappan; no. B13708-57; used with Q672L1078 for

8 and 10 ton heat pumps with 2 compressors. None

Table 6. T872-T874 Thermostat Cross Reference.

Model Number Description T874 Trade

ReplacementaRemarks

aWhen replacin

a T872 Thermostat and Q672 Subbase, alwa

s replace both the thermostat and the subbase.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—836

G1208 Marvair lo

o; special for Crispaire; used with

Q672F1166, F1323. Y594G1393

G1216 Janitrol lo

o; no. 26G05; sta

e 2 heat anticipator

set at 1.2A; used with Q672F1117. Y594G1252 Wirin

differences

(

old=new

)

: C=X.

G1224 TRADELINE; ad

ustable anticipator sta

e 2 heat;

fixed anticipator sta

e 1 heat and cool;

chan

eover in cool; used with Q672F1208.

Y594G1419

G1232 Heat Wave

(

Southwest Mf

)

o; sta

e 2 heat

anticipator set at 1.2A; used with Q672F1224.

G1240 Lennox; fast c

cle anticipator sta

e 2 heat; used

with Q672F1240. None

G1257 Carrier lo

o; no. HH07AT073; used with

Q672L1169

(

HH93AZ071

)

.None

G1265 Addison lo

o; used with Q672F1265. Y594G1252 Wirin

differences

(

old=new

)

: C=X.

G1273 Carrier lo

(

DoD model

)

; 68°F

(

20°C

)

maximum

heatin

; 78°F

(

26°C

)

minimum coolin

; used with

Q672L1052, J1054

See subbase description for

replacement information.

G1281 Wesco lo

o; used with Q672F1265. Y594G1252 Wirin

differences

(

old=new

)

: C=X.

G1299 York lo

o; meets DoD specs; used with

Q672L1177. Y594G1567

G1307 Carrier; no. 38EQ1900; Celsius; used with

Q672J1054, L1052. See subbase description for

replacement information.

G1315 Luxaire special; sta

e 2 heat anticipator set to

1.2A; used with Q672F1281. Y594G1252

G1323 Lennox special; used with Q672L1201 and

C815A1013. None

G1331 York; used with Q672J1021. Y594G1567 Wirin

differences

(

old=new

)

X=X1, L=X2, W=E; Y1-W1 and Y2-

umpers re

uired.

G1356 Westin

house; used with Q672L1219. T874D1165/

Q674F1022 Wirin

differences

(

old=new

)

X=X1, L=X2, W=E; Y1-W1 and Y2-

umpers re

uired.

G1364 York; used with Q672D1077. None

G1372 Tappan/Janitrol lo

o; no. B-13708-521;

used with Q672F1117. Y594G1252 Wirin

differences

(

old=new

)

: C=X.

G1398 York lo

o; no. 025-21454C; used with Q672J1021. Y594G1567

T872H Heat pump model; 1 sta

e heat,

1 sta

e cool, 1 sta

e chan

eover.

H1009 Command-Aire lo

o; fixed anticipator sta

e 1 heat

and cool; chan

eover with coolin

; used with

Q672C1086.

Y594H1012

H1017 Friedrich lo

o. Y594H1012

H1025 Friedrich lo

o; Celsius. Y594H1012

T872M 1 sta

e heat, 1 sta

e cool with sta

e 2 heat factor

set at 60°F

(

16°C

)

M1003 Standard OEM; used with Q672D and external

switchin

means. T874C1125 T874C1125 has 12°F

(

6.7°C

)

differential between sta

e 1 and

sta

e 2 heat.

T872N Heat pump model; 2-sta

e heat, 1-sta

e cool plus

chan

eover, chan

eover in heat mode.

N1002 None

Table 6. T872-T874 Thermostat Cross Reference.

Model Number Description T874 Trade

ReplacementaRemarks

aWhen replacin

a T872 Thermostat and Q672 Subbase, alwa

s replace both the thermostat and the subbase.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

37 60-2485—8

N1010 Williamson lo

o; ad

ustable anticipator sta

e 1

and 2 heat; fixed anticipator sta

e 1 cool; used

with Q672F1133 or F1315.

T874N1016/

Q674F1220

N1028 TRADELINE heat mode chan

eover; used with

Q672F1216. T874N1016

N1036 Bard; used with Q672F1299. T874N1016/

Q674F1220

N1044 Thermotron lo

o; 1st sta

e chan

eover heat

mode; used with Q672F1299. T874N1016/

Q674F1220

T872Q 1-sta

e heat; used with another T872 for heatin

setback.

Q1009 Standard OEM T874C1125

Q1017 York lo

o T874C1125 Replacement onl

ood for

1-sta

e heat and 1-sta

e cool

applications.

Q1025 ITT lo

oNone

Q1033 Lennox lo

o; no. P-8-8899. None

Q1041 Lennox lo

o; no. 63A6401. None

T872R Heat pump model; 2-sta

e heat, 1-sta

e cool,

manual chan

eover.

R1008 Fixed anticipator sta

e 1 heat and cool; no

anticipator sta

e 2 heat; chan

eover with coolin

;

used with Q672B1046.

Y594R1425 Wirin

differences

(

old=new

)

W=W2; W1-Y1

umper re

uired.

R1016 Addison same as T872R1008; used with

Q672B1103. Y594R1425 Wirin

differences

(

old=new

)

W=W2; W1-Y1

umper re

uired.

R1024 Lennox lo

o; fast c

cle sta

e 2 heat; fixed

anticipator sta

e 1 heat and cool; chan

eover with

coolin

; used with Q672B1160 and Q672L1003.

See subbase description for

replacement information.

R1032 York lo

o; fixed anticipator sta

e 1 and 2 heat and

sta

e 1 cool; chan

eover with coolin

; used with

Q672L1011.

Y594R1664

R1040 Lennox lo

o; fast c

cle sta

e 2 heat; fixed

anticipator sta

e 1 heat and cool; isolated sta

e 2

heat switch; chan

eover with coolin

; used with

Q672B1202 no. P-8-11221, Q672L1029

See subbase description for

replacement information.

R1057 TRADELINE; fixed anticipator sta

e 1 heat and

cool; no anticipator sta

e 2 heat; chan

eover on

coolin

; used with Q672L1037; outdoor reset.

Y594R1763 Desi

ned for use on General

Electric heat pumps. Wirin

differences

(

old=new

)

: A=T.

R1065 Ad

ustable anticipator sta

e 2 heat; fixed

anticipator sta

e 1 heat and cool; chan

eover on

coolin

; used with Q672L1045.

Y594R1243

R1073 Lennox lo

o; no. 63A0301; Celsius scale;

separate auxiliar

heat power circuit; fast c

cle

sta

e 2 heat antic.

None

R1081 Ruud lo

o; same circuit as T872R1065; used with

Q672L1045, L1136. Y594R1243

R1099 Dunham Bush special; used with Q672L1060,

L1383. Y594R1243

R1107 Rheem; no. RXMT-B70; used with Q672L1045,

L1136. Y594R1243

R1115 Friedrich lo

o; fixed anticipator; used with

Q672B1244, L1086. See subbase description for

replacement information.

Table 6. T872-T874 Thermostat Cross Reference.

Model Number Description T874 Trade

ReplacementaRemarks

aWhen replacin

a T872 Thermostat and Q672 Subbase, alwa

s replace both the thermostat and the subbase.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—838

R1123 York lo

o; no. 025-21453C; Celsius scale. Y594R1664

R1131 Lennox lo

o; separate auxiliar

heat power circuit;

fast c

cle sta

e 2 heat anticipator; outdoor reset;

used with Q672L1144, C815A1013.

None

R1149 Westin

house lo

o; ad

ustable sta

e 2 heat

anticipator; coolin

chan

eover; fixed anticipator

sta

e 1 heat and cool; used with Q672L1110,

L1128, L1151.

Y594R1243 Wirin

differences

(

old=new

)

W=W2.

R1156 Marvair lo

o; used with Q672L1094, L1250. Y594R1243 Replacement has auto fan in

Emer

enc

Heat mode.

R1164 Bard; used with Q672L1185. Y594R1243

R1172 Heil Quaker; used with Q672L1193. Y594R1243 Wirin

differences

(

old=new

)

: B=X,

W=W2.

R1180 York; Celsius; used with Q672L1011. Y594R1664

R1198 TRADELINE; used with Q672L1227 Y594R1243

R1206 For use with W89; used with Q672L1235. None

R1214 Intertherm lo

o; used with Q672L1276. Y594R1300 Wirin

differences

(

old=new

)

W1=B, Z=L, K=E.

R1222 York lo

o; used with C815A1039; ad

ustable

anticipator sta

e-2 heat; used with Q672L1284 Y594R1672

R1230 Amana lo

o; no. C62397-1; used with

Q672L1300, W89. None

R1255 Sin

er lo

o; used with Q672L1326 and W89. None

R1271 Westin

house lo

o; used with Q672L1375 and

W89. Y594R1664

R1297 York; Celsius scale; used with Q672L1011. None

R1305 Used with Q672L1235 and W89. None

R1321 Duotherm lo

o; used with Q672L1409, and W89. None

R1339 Williamson; used with Q672L1391. Y594R1243

T872S Heat pump model; 2-sta

e heat plus chan

eover,

1-sta

e cool.

S1005 Westin

house lo

o; ad

ustable anticipator sta

e 1

and 2 heat; fixed anticipator sta

e 1 heat;

chan

eover with heatin

: used with Q672C1045

T874C1018/

Q674C1058 Wirin

differences

(

old=new

)

V=RC-RH, F=G, C=Y1, Z=B,

H2=W2; W1-Y1

umper re

uired.

T872T 1-heat sta

e, 1-vent and 2-cool sta

es.

T1004 Trane lo

o; used with Q672B1129. None

T872W 3-heat sta

es, 2-cool sta

es, manual chan

eover

W1019 Lennox lo

o; no. 52C7501; used with Q672L1342

and C815A1013. None

W1027 Westin

house lo

o; used with Q672L1268 and

C815A1021. None

W1035 TRADELINE; used with C815A1043 and

Q672B1251. Y594W1014

Table 6. T872-T874 Thermostat Cross Reference.

Model Number Description T874 Trade

ReplacementaRemarks

aWhen replacin

a T872 Thermostat and Q672 Subbase, alwa

s replace both the thermostat and the subbase.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

39 60-2485—8

Table 7. Q672-Q674 Subbase Cross Reference.

Model Number Description Q674 Trade

ReplacementaRemarks

Q672A S

stem: HEAT-AUTO-COOL, Fan: AUTO-ON

A1005 Standard OEM Q674A1019

A1013 TRADELINE Q674A1019

A1021 RC-RH

umper Q674A1019 RC-RH

umper re

uired.

A1039 RC-RH

umper; Chek Lite Q674A1019 RC-RH

umper re

uired.

Q672B S

stem: HEAT-OFF-COOL, Fan: AUTO-ON

B1004 Standard OEM Q674B1034

B1012 Isolated G terminal. Q674B1018

B1020 S

stem: HEAT-OFF-RESET-COOL Q674B1034 Used s

stem off as reset position.

B1038 TRADELINE Q674B1034

B1046 Heat pump circuit; used with T872R1008. Y594R1425 Wirin

differences

(

old=new

)

W1=Y1, W=W2.

B1053 RC-RH

umper Q674B1034 RC-RH

umper re

uired.

B1061 Chek Lite Q674B1034

B1079 Auto fan operation in heat and cool. Q674B1075

B1087 Carrier no. HH93AZ078; RC-RH

umper. Q674B1075

B1095 Carrier no. HH93AZ084; RC-RH

umper. Q674B1034

B1103 Addison; heat pump circuit; used with

T872R1016. Y594R1425 Wirin

differences

(

old=new

)

W=W2; W1-Y1

umper re

uired.

B1111 Carrier no. HH93AZ080; isolated G terminal. Q674B1018

B1129 Trane special circuit; used with T872T1004. None

B1137 RC-RH

umper; isolated G terminal. Q674B1018 RC-RH

umper re

uired.

B1145 Fedders special Q674B1034 RC-RH

umper re

uired.

B1152 Fedders special; auto fan operation in heat

and cool. Q674B1075

B1160 Lennox; heat pump circuit; used with

T872R1024; includes compressor lockout in

EM. HT.

Y594R1243 Wirin

differences

(

old=new

)

V-VR=R, M=Y, Y=W2, F=G, R=O.

B1178 General Electric no. AY28X107; auto fan

operation in heat and cool. Q674B1075

B1186 Trane; isolated G terminal; Filter LED. Q674B1018

B1194 General Electric no. AY28X124; auto fan

operation in heat and cool. Q674B1075 Set T874 sta

e-1 anticipator for

combined load of heat rela

and fan

rela

B1202 Lennox no. P-8-11223; heat pump circuit; used

with T872R1040. Y594R1243 Wirin

differences

(

old=new

)

V-VR=R, M=Y, Y=W2, F=G, R=O.

B1210 None

B1228 General Electric no. BAY28X137; isolated

G terminal. Q674B1018

B1236 Carrier no. HH-93AZ079; RC-RH

umper;

LOCKOUT LED indicates compressor lockout

switch activated.

Q674B1034 RC-RH

umper; LED cannot be

provided in TRADELINE model.

B1244 Friedrich; heat mode chan

eover; used with

T872R1115. T874C1018/

Q674B1034 Wirin

differences

(

old=new

)

: C=no

connection; RC-RH and W1-Y1

umpers re

uired.

B1251 Used with T872W1035 and C815A1043. Y594W1014

aWhen replacin

a T872 Thermostat and Q672 Subbase, alwa

s replace both the thermostat and subbase.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—840

B1269 Whalen; Hi-Lo fan switch; constant fan in heat

and cool s

stem switch positions; used with

T872C1574.

None

B1277 S

uare D no. HCB-5. Q674B1034

B1285 Wards; RC-RH and F-W3

umpers; used with

T872C1673. Gas Furnace:

T874C1018/

Q674B1034

Electric Furnace:

T874C1018/

Q674B1075

ust anticipator

faster

for correct

performance.

B1293 Lennox no. 41C96; used with T872C1673. Same as

Q672B1285

Q672C S

stem: OFF-AUTO, Fan: AUTO-ON

C1003 Standard OEM Q674C1058

C1011 Westin

house; RC-RH

umper. Q674C1058 RC-RH

umper re

uired.

C1029 W1-Y2

umper; for heat pump; used with

T872D1136. Q674E1049 Replacement has heat/cool s

stem

switchin

C1037 Chr

sler Airtemp; S

stem: COOL-OFF-AUTO. Q674C1058

C1045 Westin

house; heat pump; used with

T872S1005. T874C1018/

Q674C1058 Wirin

differences

(

old=new

)

V=RC-RH, F=G, C=Y1, Z=B,

H2=W2; W1-Y1

umper re

uired.

C1052 Isolated sta

e 2 heat circuit for dc electric heat

rela

.Recontrol Use T874G1246/Q674F1212 which

adds HEAT-COOL-EM.HT. s

stem

switch.

C1060 Fedders special. Q674C1058

C1078 General Electric no. AY28X109. Q674C1058

C1086 Command-Aire; heat pump; used with

T872H1009. Y594H1012

C1102 TRADELINE Q674C1058

Q672D S

stem: None. Fan: None.

D1002 Standard OEM; used with T872F1126. Q674D1040

D1010 Lennox special. None

D1028 Carrier; RC-RH

umper. None

D1036 Carrier no. HH93AZ070; RC-RH

umper. Q674D1040 RC-RH

umper re

uired.

D1044 General Electric no. AY-28X100. None

D1069 S

uare D no. HCB-4. None

D1077 York; used with T872G1364. None

D1085 TRADELINE Q674D1040

Q672E S

stem: OFF-HEAT-AUTO-COOL

Fan: AUTO-ON

E1001 Standard OEM Q674E1049

E1019 Lennox no. P-8-8892; heat pump; cool mode

chan

eover; used with T872G1026. T874D1165/

Q674B1075

E1027 Heat pump circuit; W1-Y2

umper; cool mode

chan

eover; used with T872G1018. Y594G1393 Wirin

differences

(

old=new

)

: Y1=O,

Y2=Y.

E1035 Heat pump circuit; W1-Y2

umper; cool mode

chan

eover. Y594G1393 Wirin

differences

(

old=new

)

: Y1=O,

Y2=Y.

E1043 Heat pump circuit; heat mode chan

eover. Q674E1049 Wirin

differences

(

old=new

)

W1=B, W2=W1; W1-Y1

umper.

Table 7. Q672-Q674 Subbase Cross Reference.

Model Number Description Q674 Trade

ReplacementaRemarks

aWhen replacin

a T872 Thermostat and Q672 Subbase, alwa

s replace both the thermostat and subbase.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

41 60-2485—8

E1050 TRADELINE Q674E1049

E1068 RC-RH

umper; used with T872C1699. Q674E1049 RC-RH

umper re

uired.

E1076 RC-RH internal

umper; EM. HT. LED. Q674E1049 RC-RH

umper re

uired.

E1084 Carrier no. HH93AZ076; RC-RH

umper. Q674E1049 RC-RH

umper re

uired.

E1092 Carrier no. HH93AZ082; RC-RH

umper; B

terminal; isolated G terminal. Q674E1049

E1100 General Electric no. AY28X099. Q674E1049

E1118 Airtemp; heat pump; used with T872D1169. T874D1165/

Q674E1049 Wirin

differences

(

old=new

)

A=W1; set H1 anticipator to 1.2A.

E1126 Common R terminal. Q674E1049 RC-RH

umper re

uired.

E1134 ITT Nesbitt; RC-RH

umper; O and B terminals;

isolated G terminal. Q674E1049

E1142 Lennox no. P-8-11224; heat pump;

V-VR

umper; cool mode chan

eover; used with

T872G1067.

Y594G1252 Wirin

differences

(

old=new

)

V-VR=R, Y=W2, R=O, M=Y, F=G.

E1159 Carrier no. HH93AZ077; RC-RH

umper;

LOCKOUT LED indicates activation of

compressor lockout switch.

Q674E1049 RC-RH

umper re

uired; no LED in

TRADELINE model.

E1167 S

uare D no. HCB-2; Chek Lite. Q674E1049

E1183 S

uare D no. HCB-3. Q674E1049

E1191 Lennox; HIGH and LOW LEDs; used with

T872D1045. Q674E1049 No LEDs on replacement.

Q672F S

stem: EM. HT.-HEAT-AUTO-COOL-OFF

Fan: AUTO-ON.

F1000 With EM. HT. LED; used with T872C1699. Q674F1022 Remove W3-X2

umper to E-X2.

F1018 Heat pump; heat mode chan

eover; Chek Lite;

used with T872G1000. Y594G1252 Wirin

differences

(

old=new

)

W=W2, X1=X.

F1026 Chek Lite; W2-X2

umper. Q674F1022

F1034 Airtemp; EM. HT. LED; RC-RH and X2-E

umpers. Q674F1022 If RC-RH

umper removed on

Q672F1034, Q674F1022 does not

replace.

F1042 W2-X2

umper; Chek Lite. Q674F1022

F1059 Carrier no. HH93AZ074; EM. HT. LED. Q674F1022 Remove W2-X2

umper to E-X2; X

terminal same as C.

F1067 Lennox; heat pump; cool mode chan

eover;

EM. HT. LED; used with T872G1026. None

F1075 Heat pump circuit; EM. HT. LED; 2 terminal; RC-

umper. None

F1083 Lennox no. P-8-11225; heat pump;

V-VR

umper; cool mode chan

eover; EM. HT.

LED; used with T872G1067.

None

F1091 Westin

house; heat pump; EM. HT. LED; cool

mode chan

eover; compressor lockout in

EM. HT.; used with T872G1034.

Y594G1252 Wirin

differences

(

old=new

)

W=W2.

F1109 Airtemp no. 3778567ACC; R-X2

umper;

EM. HT. LED. Q674F1022 R-X2

umper re

uired.

F1117 Tappan no. 080-13708-53; heat pump; EM. HT.

LED; cool mode chan

eover; compressor

lockout and auto fan in EM. HT.; used with

T872G1109, G1216, G1372.

Y594G1252 Wirin

differences

(

old=new

)

: C=X.

Table 7. Q672-Q674 Subbase Cross Reference.

Model Number Description Q674 Trade

ReplacementaRemarks

aWhen replacin

a T872 Thermostat and Q672 Subbase, alwa

s replace both the thermostat and subbase.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—842

F1125 BDP no. 3442DP90; used with T872G1117,

G1166, G1174. Y594G1252 Wirin

differences

(

old=new

)

: C=X.

F1133 Williamson; heat pump; EM. HT. LED; heat

mode chan

eover; compressor lockout in

EM. HT.; used with T872N1010.

T874N1016/

Q674F1220

F1141 Westin

house; EM. HT. LED; auto fan in

EM. HT.; used with T872G1034. Y594G1252 Wirin

differences

(

old=new

)

W=W2.

F1158 Rheem Ruud; heat pump; EM. HT. LED; cool

mode chan

eover; compressor lockout in

EM. HT.; used with T872G1083, G1133, G1141;

auto fan in EM. HT.

Y594G1252

F1166 Crispaire; EM. HT. LED; used with T872G1208. Y594G1252

F1174 Carrier no. HH93AZ081; EM. HT. LED. Q674F1022

F1182 S

uare D no. HCB-1; Chek Lite; R-X2

umper;

stem: Aux. Heat replaces EM. HT. Q674F1022 R-X2

umper; add monitor switch

between X1 and low side of power.

F1190 EM. HT. LED; X2-E and RC-RH

umpers. None

F1208 TRADELINE; cool mode chan

eover; EM. HT.

LED; used with T872G1224. Y594G1419

F1216 TRADELINE; heat mode chan

eover; EM. HT.

LED; used with T872N1028. T874N1016/

Q674F1220

F1224 Heatwave

(

Southwest Mf

)

; compressor

lockout in EM. HT.; EM. HT. LED; used with

T872G1232.

Y594G1252

F1232 Rheem; cool mode chan

eover; EM. HT. and

AUX. HEAT LEDs; compressor lockout in

EM. HT.; used with T872G1133.

Y594G1252

F1240 Lennox; cool mode chan

eover; EM. HT. and

SERVICE LEDs; used with T872G1240. None

F1257 Westin

house; cool mode chan

eover;

EM. HT. and AUX. HEAT LEDs; auto fan in

EM. HT; used with T872G1034.

Y594G1252 Wirin

differences

(

old=new

)

W=W2.

F1265 Wesco Addison; Chek and EM. HT. LEDs; used

with T872G1281, G1265. Y594G1252 Wirin

differences

(

old=new

)

: C=X.

F1273 Southwest special; no. 0361-136; W2-X2

umper. None

F1281 Luxaire special; used with T872G1315. Y594G1252

F1299 Bard special; used with T872N1036, N1044. T874N1016/

Q674F1220

F1315 Williamson special; used with T872N1010. T874N1016/

Q674F1220

F1323 Crispaire special; used with T872G1208. Y594G1252

Q672G S

stem: OFF-AUTO. Fan: None.

G1009 Standard OEM Q674G1070

G1017 Sin

er; O-B

umper; used with T872D1375. Q674G1070

G1025 Includes O and B terminals. Q674G1070

G1033 General Electric no. AY28X102. Q674G1070

G1041 Sin

er no. 02005649; French wordin

; O-B

umper. Q674G1070 Less French wordin

G1066 SLI-Mammoth; heat pump; heat mode

chan

eover. Q674G1070 Connect fan

(

)

wire to Y1 terminal;

B-O and RC-RH

umpers.

Table 7. Q672-Q674 Subbase Cross Reference.

Model Number Description Q674 Trade

ReplacementaRemarks

aWhen replacin

a T872 Thermostat and Q672 Subbase, alwa

s replace both the thermostat and subbase.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

43 60-2485—8

G1074 Sin

er no. 02005754; X1 and X2 terminals for

field-added indicator li

hts; used with

T872D1375.

None

G1082 Sin

er no. 02005792; X1 and X2 terminals for

field-added indicator li

hts; used with

T872D1375.

None

G1090 TRADELINE; B and O terminals. Q674G1070

Q672H S

stem: OFF-ON

Fan: NIGHT INT.-DAY CONT.

H1008 Used with T872. None

Q672J S

stem: EM. HT.-AUTO-OFF

Fan: AUTO-ON.

J1005 With EM. HT. LED; used with T872C or D. None

J1013 Westin

house; heat pump; EM. HT. LED; cool

mode chan

eover; compressor lockout in

EM. HT.; used with T872G1034.

Y594G1252

J1021 York; heat pump; EM. HT. LED; cool mode

chan

eover; compressor lockout and auto fan in

EM. HT.; E-W

umper; used with T872G1042,

G1331, G1398.

Y594G1567

J1039 Heat pump; EM. HT. and AUX. HEAT LEDs;

cool mode chan

eover; compressor lockout and

auto fan in EM. HT.; used with T872G1059.

Y594G1161 Desi

ned for use on General

Electric heat pumps.

J1047 Sin

er no. 02005699; heat pump; EM. HT. LED;

heat mode chan

eover. Q674F1022

J1054 Carrier no. HH93AZ073A; heat pump; EM. HT.

LED; cool mode chan

eover; compressor

lockout in EM. HT.; used with T872G1075,

G1182, G1307.

Y594G1252 Wirin

differences

(

old=new

)

: C=X.

J1062 Westin

house; EM. HT. and AUX. HEAT LEDs;

used with T872G1034. Y594G1252 Wirin

differences

(

old=new

)

W=W2.

Q672K S

stem: OFF-HEAT-AUTO-COOL. Fan: None.

K1004 Carrier no. HH93AZ072. Q674E1049 Fan switch does not function.

K1012 Oneida Heater no. 30A0288-01; S

stem: OFF-

WOOD-WOOD/OIL-OIL; used with T872F1175. T874F1155/

Q674K1026

Q672L S

stem: EM. HT.-HEAT-OFF-COOL.

Fan: ON-AUTO.

L1003 Lennox; heat pump; EM. HT. LED; cool mode

chan

eover; used with T872R1024. Y594R1425

L1011 York; heat pump; EM. HT. LED; cool mode

chan

eover; compressor lockout and auto fan in

EM. HT.; used with T872R1032, R1180, R1297.

Y594R1664

L1029 Lennox no. P-8-11226; heat pump; EM. HT.

LED; V-VR

umper; cool mode chan

eover;

compressor lockout in EM. HT.; used with

T872R1040.

Y594R1425 Wirin

differences

(

old=new

)

V-VR=R, M=Y, Y=W2, F=G, R=O.

L1037 Heat pump; EM. HT. and AUX. HT. LEDs; cool

mode chan

eover; compressor lockout and auto

fan in EM. HT.; used with T872R1057.

Y594R1763 Wirin

differences

(

old=new

)

: A=T;

desi

ned for used on General

Electric heat pumps.

L1045 Rheem; heat pump; EM. HT. LED; cool mode

chan

eover; compressor lockout in EM. HT.;

auto fan in EM. HT; used with T872R1065,

R1081, R1107.

Y594R1243

Table 7. Q672-Q674 Subbase Cross Reference.

Model Number Description Q674 Trade

ReplacementaRemarks

aWhen replacin

a T872 Thermostat and Q672 Subbase, alwa

s replace both the thermostat and subbase.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—844

L1052 Carrier no. HH93AZ075; heat pump; EM. HT.

LED; cool mode chan

eover; compressor

lockout in EM. HT.; used with T872G1075,

G1182, G1273, G1307.

Y594R1615 Wirin

differences

(

old=new

)

: C=X.

L1060 Dunham Bush; EM. HT. LED; used with

T872R1099. Y594R1243

L1078 Tappan no. B13708-58; heat pump; EM. HT.

LED; cool mode chan

eover; compressor

lockout in EM. HT.; EM. HT. rela

provides fan

operation in EM. HT.; used with T872G1190.

None

L1086 Friedrich; heat mode chan

eover; EM. HT. LED;

used T872R1115 with L terminal. Y594R1243 Wirin

differences

(

old=new

)

: X2=E,

C=X.

L1094 Crispaire; W2-H

umper; EM. HT. LED; used

with T872R1065, R1156. Y594R1243 Replacement has auto fan in

Emer

enc

Heat mode.

L1102 Fedders; heat mode chan

eover; EM. HT. LED;

used with T872C1509, C1517, C1541. Y594R1425 Wirin

differences

(

old=new

)

: K=E,

C=X; remove Y-W1

umper.

L1110 Westin

house; EM. HT. LED; used with

T872R1149. Y594R1243 Wirin

differences

(

old=new

)

W=W2.

L1128 Westin

house; EM. HT. LED; used with

T872R1149. Y594R1243 Wirin

differences

(

old=new

)

W=W2.

L1136 Rheem no. 41-20796-07; cool mode

chan

eover; EM. HT. and AUX. HT. LEDs; used

with T872R1081, T872R1107.

Y594R1243

L1144 Lennox; V-VR

umper; EM. HT. and SERVICE

LEDs; isolated sta

e 2 heat; used with

T872R1131, C815A1013.

None

L1151 Westin

house; AUX. HT. and EM. HT. LEDs;

used with T872R1149. Y594R1243 Wirin

differences

(

old=new

)

W=W2.

L1169 Carrier no. HH93AZ071; EM. HT. LED; used

with T872G1257

(

HH07AT073

)

.None

L1177 York; DoD; EM. HT. LED; used with T872G1299. Y594G1567

L1185 Bard; used with T872R1164. Y594R1243

L1193 Heil Quaker no. NAXA001TS01; used with

T872R1172. Y594R1243 Wirin

differences

(

old=new

)

: B=X,

W=W2.

L1201 Lennox special; no. 1485701; used with

T872G1323. None

L1219 Westin

house special; used with T872G1356. T874D1165/

Q674F1022 Wirin

differences

(

old=new

)

: X=X1,

L=X2, W=E; Y1-W1 and

Y2-W2

umpers re

uired.

L1227 Heat pump; used with T872R1198. Y594R1243

L1235 Intertherm; used with T872R1206, R1305. None

L1250 Crispaire special; used with T872R1156 and

C815A1021. Y594R1243

L1268 Westin

house special; used with T872W1027

and C815A1021. None

L1276 Intertherm special; used with T872R1214. Y594R1300 Wirin

differences

(

old=new

)

W1=B, Z=L, K=E.

L1284 York special; used with T872R1222. Y594R1672

L1300 Amana special; no. C62345-1; used with

T872R1230. None

L1326 Sin

er; used with T872R1255. None

Table 7. Q672-Q674 Subbase Cross Reference.

Model Number Description Q674 Trade

ReplacementaRemarks

aWhen replacin

a T872 Thermostat and Q672 Subbase, alwa

s replace both the thermostat and subbase.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

45 60-2485—8

L1342 Lennox no. 52C7601; used with T872W1019

and C815A1013. None

L1375 Westin

house; used with T872R1271, W89. None

L1383 Dunham Bush; used with T872R1099. Y594R1243

L1391 Williamson; used with T872R1339. Y594R1243

L1409 Duotherm special; used with T872R1321, W89. None

Q672N S

stem: OFF-HEAT-COOL-EVAP.

N1001 Goettl; heat pump; heat mode chan

eover;

evaporative cooler circuit; Fan: AUTO-ON;

stem: AUTO; used with T872C1459.

None

N1019 Goettl; heat pump; heat mode chan

eover;

evaporative cooler circuit; W1-Y1

umper; used

with T872C1459.

None

N1027 Sie

ler special; used with T872C1707. None

Q672P S

stem: EM. HT.-HEAT-COOL.

P1009 Carrier special; no. HH93AZ069; used with

T872G1075

(

HH07AT071

)

.Y594R1243 Replacement has OFF s

stem

switch position

Table 7. Q672-Q674 Subbase Cross Reference.

Model Number Description Q674 Trade

ReplacementaRemarks

aWhen replacin

a T872 Thermostat and Q672 Subbase, alwa

s replace both the thermostat and subbase.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—846

Table 8. T874 Cross Reference.

Model

Number Fig.

No. Description Trade Model

Replacement Remarks

T874A 1-sta

e heat, 1-sta

e cool.

A1002 44, 65 Hone

well lo

o; Standard OEM; used with Q674B1331. T874A1036

A1010 44 Hone

well lo

o; includes Allen wrench and screws to

lock cover; non-ad

ustable ran

e stops set at 72°F

(

max.

heat

)

and 78°F

(

min. cool

)

(

22-26°C

)

; field ad

ustable

lockin

levers.

T874A1010

A1028 44 Hone

well lo

o; heat anticipator factor

set at 0.4A. T874A1036

A1036 44 Hone

well lo

o; TRADELINE® model; includes Allen

wrench and screws to lock cover; field ad

ustable

lockin

levers.

T874A1036

A1044 44 Obsolete. AAF/Sn

der General lo

o; part no. 4ELN-

3006C; °F/°C scaleplate. T874A1036 Replacement has °F

scaleplate.

A1051 44 Lennox lo

o; part no. 12F9901; °F/°C scaleplate; heat

anticipator set at 0.45A. T874A1036 Replacement has °F

scaleplate.

A1069 44 Obsolete. Westin

house lo

o; used with Q674A-E,G. T874A1036

A1077 46, 82 Obsolete. Amana Air Conditionin

o; part no.

D68535-1; heat anticipator factor

set at 1.2A; used with

Q674B1075, E1056; used in Y594A1001, A1019.

T874A1036

A1085 44, 46,

55, 66 Obsolete. Trane lo

o; part no. 13510451; used with

Q674B1018, B1075, D1008. T874A1036

A1093 44 Obsolete. McQua

o; part no. 02005935; °F/°C

scaleplate. T874A1036 Replacement has °F/°C

scaleplate.

A1101 51, 53 Carrier lo

o; part no. HH07AT174; used with Q674B. Y594C1421 or

T874A1036a

When usin

the T874C1036,

set sta

e 1 heat anticipator for

total current draw of fan and

sta

e 1 heat primar

A1119 82 Obsolete. Sears lo

o; part no. 541. 91441/49. 9144; °F/

°C scaleplate; used with Q674E1007; used in

Y594A1068.

T874A1036 Replacement has °F

scaleplate.

A1127 44 Obsolete. Climate Control lo

o; part no. 02005936; °C

scaleplate. T874A1036 Replacement has °F

scaleplate.

A1135 44 Fedders multi-lo

o; part no. THTX-110-WCHA,

88-58-00500-001. T874A1036

A1143 44 Hone

well lo

o; °C scaleplate. T874A1036 Replacement has °F

scaleplate.

A1150 44 Hone

well lo

o; TRADELINE model; includes Allen

wrench and screws to lock cover; field ad

ustable

lockin

levers

(

68°F max. heat, 78°F min. cool

)

T874A1150

A1168 44 Obsolete. Trane Comfort Corps lo

o. T874A1036

A1176 44 Hone

well lo

o; meets DoD specs; includes Allen

wrench and screws to lock cover; no thermometer; non-

ustable ran

e stops set at 72°F

(

max. heat

)

and 78°F

(

min. cool

)

(

22-26°C

)

; field ad

ustable lockin

levers.

T874A1176

A1184 51, 53 Trane lo

o; part no. BAY28X182; °F/°C scaleplate;

automatic fan in heatin

and coolin

modes; heat

anticipator set at 0.4A; used with Q674B1141, E1080.

T874A1036aWhen used with Q674E1080,

set sta

e 1 heat anticipator for

total current draw of fan and

sta

e 1 heat primar

;

replacement has °F

scaleplate.

A1192 44 Obsolete. Lennox lo

o; part no. 13F0001; °C scaleplate;

heat anticipator factor

set at .458A. T874A1036 Replacement has °F

scaleplate.

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

47 60-2485—8

A1200 51, 53 Obsolete. Carrier lo

o; part no. HH07AT164; °C

scaleplate; includes Allen wrench and screws to lock

cover; used with Q674B.

T874A1036aSet sta

e 1 heat anticipator for

total current draw of fan and

sta

e 1 heat primar

;

replacement has °F

scaleplate.

A1226 44 Hone

well lo

o; Hone

well Canada TRADELINE model;

°C scaleplate; includes Allen wrench and screws to lock

cover.

T874A1036 Replacement has °F

scaleplate.

A1234 44 Obsolete. Friedrich Climate Master lo

o; heat

anticipator factor

set 1.2A. T874A1036

A1242 44 Obsolete. Friedrich Climate Master lo

o. T874A1036

A1259 44 Obsolete. Wesco lo

o; heat anticipator set at 0.8A. T874A1036

A1267 59 Obsolete. McQua

o; used with Q674Q1004. T874A1036

A1275 44 Obsolete. Lennox lo

o; part no. 13F0101; meets DoD

specifications. T874A1176

A1283 75 McQua

Air Conditionin

o; part no. 03005047; used

with Q674C1132 and thermistor to displa

outdoor

temperature.

T874A1036 Replacement does not have

abilit

to displa

external

temperature or momentar

stem switch position.

A1291 64 No lo

o; three-speed fan; one setpoint lever for heat and

cool setpoints; used with Q674Q1012; used in

Y594A1126.

T874A1036/

Q674B1075a

Replacement has two levers

and 1 speed fan.

A1309 44 Obsolete. Arcoaire Air Conditionin

and Heatin

part no. AO2076; includes Allen wrench and screws to

lock cover.

T874A1036

A1317 44 Obsolete. McQua

o; part no. 60685301; no

scaleplate; used with Q674A-E,G. T874A1036

A1325 75 Obsolete. McQua

o; part no. 60685401; no

scaleplate; used with Q674C1306 and outdoor

thermistor to displa

outdoor temperature.

T874A1036 Replacement does not have

abilit

to displa

external

temperature or momentar

stem switch position.

A1341 44 Obsolete. Trane lo

o; part no. THT-0577; meets DoD

specifications. T874A1176

A1358 44 York-Miraco lo

o. T874A1036

A1366 51, 53 Obsolete. BDP Multi-lo

o; part no. HH07AT182. T874A1036aSet sta

e 1 heat anticipator for

total current draw of fan and

sta

e 1 heat primar

A1374 44 American Standard lo

o; part no. ASYSTAT610; heat

anticipator factor

set at 0.4A. T874A1036a

A1390 44 Obsolete. Climate Control lo

o; part no. 654958804; °F/

°C scaleplate. T874A1036 Replacement has °F

scaleplate.

A1416 44 Obsolete. Reznor lo

o; part no. 654758803; °F/°C

scaleplate. T874A1036 Replacement has °F

scaleplate.

A1424 214 Obsolete. Carrier Ol

mpia Series Split S

stem lo

o; part

no. HH07AT194; used with Q674B1455

(

HH93AZ208

)

. See OEM for

replacement.

A1440 91 Obsolete. Simplex S

stem 2000 lo

o; heat anticipator

factor

set at 1.2A; used with Q674G1005; used in

Y594A.

T874A1036

A1465 212 Hone

well Trol-A-Temp™ lo

o; Premier White® color;

heat anticipator factor

set at 0.10A; used with

Q674E1379.

None See Trol-A-Temp for

replacement.

Table 8. T874 Cross Reference.

Model

Number Fig.

No. Description Trade Model

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—848

A1481 44 Obsolete. Hone

well lo

o; Carrier part no. HH621602;

includes lockin

cover and non-ad

ustable ran

e stops

set at 72°F

(

max. heat

)

and 78°F

(

min. cool

)

T874A1036

A1507 44 Obsolete. Climate-Tel lo

o; includes Allen wrench and

screws to lock cover and non-ad

ustable ran

e stops set

at 72°F

(

max. heat

)

and 78°F

(

min. cool

)

T874A1176

A1523 224,

225 Obsolete. AAF/Sn

der General lo

o; part no.

066804404; °F/°C scaleplate; no coolin

anticipation;

used with Q674E1312, C1298.

See OEM for

replacement.

A1549 224,

225 Obsolete. McQua

o; part no. 066816601; no coolin

anticipation; used with Q674E1312, C1298. See OEM for

replacement.

A1556 51, 53 Carrier lo

o; part no. HH07AT164-W; °C scaleplate;

Premier White® color; includes Allen wrench and

screws to lock cover; used with Q674B.

T874A1036aReplacement has °F

scaleplate; replacement is

bei

A1572 224,

225 Obsolete. McQua

o; part no. 066816611; Premier

White® color; °F/°C scaleplate; no coolin

anticipation. See OEM for

replacement.

A1580 91 California Economizer lo

o; Premier White® color; heat

anticipator factor

set at 1.2A. T874A1036

A1598 224,

225 McQua

o; part no. 073319001; Premier White®

color; °F/°C scaleplate; includes Allen wrench, screws to

lock cover and AAF insert.

See OEM for

replacement.

A1614 44 Hone

well lo

o; TRADELINE® model; °C scaleplate;

Premier White® color; includes Allen wrench and

screws to lock cover; used with Q674B.

T874A1036 Replacement has °F

scaleplate; replacement is

bei

A1622 44 Obsolete. York lo

o; part no. 2TH04703224A; includes

Allen wrench and screws to lock cover and non-

ustable ran

e stops set at 72°F

(

max. heat

)

and 78°F

(

min. cool

)

T874A1010

T874B 1-sta

e heat, 2-sta

e cool.

B1001 44 Obsolete. Hone

well lo

o. T874B1019

B1019 44 Hone

well lo

o; TRADELINE model; includes Allen

wrench and screws to lock cover. T874B1019

B1027 44 Obsolete. Westin

house lo

o. T874B1019

B1035 44, 46 Obsolete. Trane lo

o; used with Q674B1018, B1075;

used in Y594B1026, B1034. T874B1019

B1043 44 Obsolete. Hone

well lo

o; °C scaleplate. T874B1019 Replacement has °F

scaleplate.

B1050 44 Lennox lo

o; part no. 13F0201; °F/°C scaleplate. T874B1019 Replacement has °F

scaleplate.

B1068 44 Hone

well lo

o; Hone

well Canada TRADELINE model;

°C scaleplate; includes Allen wrench and screws to lock

cover.

T874B1019 Replacement has °F

scaleplate.

B1076 88 Obsolete. Lennox Power Saver Two-Speed lo

o; part

no. 91C7401; °F/°C scaleplate; used with Q674E1155. T874B1019 Replacement has °F

scaleplate.

B1084 44 Obsolete. Lennox Two-Speed lo

o; part no. 13F0301;

°C scaleplate. T874B1019 Replacement has °F

scaleplate.

B1092 44 Obsolete. Hone

well lo

o; Heil Quaker part no.

HQ521389HW. T874B1019

B1100 88 Obsolete. Janitrol lo

o; part no. CHTS36-60; °F/°C

scaleplate; used with Q674E1338; used in Y594B1042. T874B1019 Replacement has °F

scaleplate.

B1118 44 Hone

well lo

o; °C scaleplate; used with

Q674A-E, G. T874B1019 Replacement has °F

scaleplate.

Table 8. T874 Cross Reference.

Model

Number Fig.

No. Description Trade Model

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

49 60-2485—8

B1134 222 Obsolete. Carrier S

ner

2000 lo

o; part no.

HH07AT199; °C scaleplate; used with Q674E1395

(

HH93AZ209

)

T874B1019/

Q674E1049a

Wirin

differences

(

old=new

)

W1=W; RC-RH

umper

uired; replacement has no

LEDs.

T874C 2-sta

e heat, 1-sta

e cool.

C1000 44, 76 Hone

well lo

o; used with Q674B1075, C1181; used in

Y594C1058. T874C1018

C1018 60, 61,

81, 92 Hone

well lo

o; TRADELINE model; includes Allen

wrench and screws to lock cover; used with

Q674C1074.

T874C1018

C1026 44 Obsolete. AAF lo

o; °C scaleplate; includes Allen

wrench and screws to lock cover; non-ad

ustable ran

stops set at 23°C

(

max. heat and min. cool

)

(

73°F

)

T874C1018 Replacement has °F

scaleplate.

C1034 44 Lennox lo

o; part no. 13F0401; °F/°C scaleplate. T874C1018 Replacement has °F

scaleplate.

C1042 44 Obsolete. Westin

house lo

o; H1 anticipator factor

set

at.75A; H2 anticipator factor

set at 1.2A; used with

Q674A-E,G.

T874C1018

C1059 44, 142 Obsolete. Amana Air Conditionin

o; part no.

D68535-2; H1 anticipator factor

set at 1.2A; used with

Q674E1056, Q674B1059, Q674F1022; used in

Y594C1009, Y594C1017, Y594C1256, Y594C1330.

T874C1018

C1067 44 Obsolete. Sears lo

o; part no. 42. 9297; °F/°C

scaleplate. T874C1018 Replacement has °F

scaleplate.

C1075 51, 53 Carrier lo

o; part no. HH07AT170; used with

Q674B1166. Y594C1421 or

T874C1018a

When usin

the T874C1018,

set sta

e 1 heat anticipator for

total current draw of fan and

sta

e 1 heat primar

C1083 44 Obsolete. Trane lo

o; used with Q674E1007; used in

Y594C1082. T874C1018

C1117 44 Hone

well lo

o; °C scaleplate. T874C1018 Replacement has °F

scaleplate.

C1125 60, 61,

92 Obsolete. Hone

well lo

o; 12°F

(

6.7°C

)

differential

between sta

e 1 heat and sta

e 2 heat; used with

Q674G1047.

T8611M2025

C1133 96 Obsolete. AAF/Sn

der General lo

o; part no.

4ELN7546; no H1 heat anticipation; used with Q674A-

G,N and Q674C1173.

T874C1018 Must have H1 anticipator set

to maximum value.

C1141 44 Obsolete. Hone

well lo

o; meets DoD specs; includes

Allen wrench and screws to lock cover; no thermometer;

non-ad

ustable ran

e stops set at 72°F

(

max. heat

)

and

78°F

(

min. cool

)

(

22-26°C

)

; field ad

ustable lockin

levers.

T874C1141

C1158 44 Obsolete. Solaron special. T874C1018

C1166 51, 53 Obsolete. Carrier lo

o; part no. HH07AT160; °C

scaleplate; includes Allen wrench and screws to lock

cover; used with Q674B.

T874C1018aReplacement has °F

scaleplate; set sta

e 1 heat

anticipator for total current

draw of fan and sta

e 1 heat

primar

C1174 44 Obsolete. Goettl lo

o. T874C1018

C1182 60 Obsolete. Goettl lo

o; H1 anticipator factor

set at 0.8A;

used with Q674N1015. T874C1018

C1190 44 Obsolete. Lennox lo

o; part no. 13F0501; °C scaleplate. T874C1018 Replacement has °F

scaleplate.

Table 8. T874 Cross Reference.

Model

Number Fig.

No. Description Trade Model

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—850

C1216 44 Obsolete. Fasco part no. 1230-8197. T874C1018

C1224 105 Obsolete. S

uare D lo

o. T874C1018

C1240 44 Hone

well lo

o; Hone

well Canada TRADELINE model;

°C scaleplate; includes Allen wrench and screws to lock

cover.

T874C1018 Replacement has °F

scaleplate.

C1257 44 Obsolete. Sin

er part no. 0200-5931; 8°F

(

4.4°C

)

differential between H1 and H2 heat. T874C1125 Replacement has 12°F

differential between H1 and

H2 heat.

C1265 44 Obsolete. Sin

er special; °C scaleplate; 5°C

(

8°F

)

differential between H1 and H2 heat. T874C1125 Replacement has 12°F

differential between H1 and

H2 heat; replacement has °F

scaleplate.

C1273 44 Hone

well lo

o; °C scaleplate; includes Allen wrench

and screws to lock cover; non-ad

ustable ran

e stops

factor

set at 23°C

(

max. heat and min. cool

)

(

73°F

)

T874C1018 Replacement has °F

scaleplate.

C1281 44 Obsolete. Heat Wave special. T874C1018

C1307 44 Obsolete. Friedrich Climate Master lo

o. T874C1018

C1315 44 Obsolete. Wesco lo

o; heat anticipator factor

set at

0.8A. T874C1018

C1323 44 Obsolete. Le Chauffa

e Urbain special; °C scaleplate. T874C1018 Replacement has °F

scaleplate.

C1331 82, 141 Obsolete. Duotherm lo

o; used with Q674E or Q674F. T874C1018

C1349 61 Obsolete. Si

ler lo

o; used with Q674N1023. T874C1018

C1372 52 Obsolete. Hone

well lo

o; used with Q674B1190. T874C1018/

Q674B1034 For s

stems re

uirin

automatic fan in coolin

mode

onl

T874C1018/

Q674B1075 For s

stems re

uirin

automatic fan in heatin

and

coolin

C1398 105 Obsolete. Fedders lo

o; °F/°C scaleplate; used with

Q674L1090. Y594R1425aWirin

differences

(

old=new

)

K=E, C=X; replacement has °F

scaleplate.

C1406 105 Obsolete. Climatrol lo

o; °F/°C scaleplate; used with

Q674L1090. Y594R1425aWirin

differences

(

old=new

)

K=E, C=X; replacement has °F

scaleplate.

C1414 105 Obsolete. Airtemp lo

o; °F/°C scaleplate; used with

Q674L1090. Y594R1425aWirin

differences

(

old=new

)

K=E, C=X; replacement has °F

scaleplate.

C1422 187 Obsolete. Hone

well lo

o; used with Q674B1208. None

C1430 49 Obsolete. Lennox Zone Master Two-Speed lo

o; part

no. 25F7201; used with Q674B1224. T874C1018

C1448 110,

190 Obsolete. Lennox lo

o; part no. 24F5101; meets DoD

specifications; re

uires outdoor reset; used with

Q674L1165, L1355.

Y594R1763aWirin

differences

(

new=old

)

R=V-VR, Y=M, G=F, B-X,

W=Y, T=A, O=R, X2=E;

Emer

enc

Heat becomes

sta

e 1 heat source.

C1455 127 Obsolete. Williamson lo

o; used with Q674L1322. Y594R1243a

C1463 82 Obsolete. AAF lo

o; °C scaleplate. T874C1018 Replacement has °F

scaleplate.

C1471 56 Obsolete. Mammoth lo

o; part no. 71120102; used with

Q674B1257; used in Y594C1314. T874C1018

Table 8. T874 Cross Reference.

Model

Number Fig.

No. Description Trade Model

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

51 60-2485—8

C1489 121 Obsolete. Hone

well lo

o; non-ad

ustable ran

e stops

set at 75°F

(

max. heat and min. cool

)

(

24°C

)

; used with

Q674L1157.

Y594C1322a

C1497 121 Obsolete. Hone

well lo

o; meets DoD specifications;

used with Q674L1157. Y594C1322a

C1513 44 Obsolete. Bor

-Warner multi-lo

o; part no.

6TH11703124A. T874C1018

C1562 44 Obsolete. Hone

well lo

o; Heil Quaker part no.

HQ712001HW. T874C1018

C1570 45 Obsolete. Williamson lo

o; used with Q674B1000; used

in Y594C1280. T874C1018

C1638 121 Obsolete. Hone

well lo

o; meets DoD specifications;

includes Allen wrench and screws to lock cover; no

thermometer; non-ad

ustable ran

e stops set at 72°F

(

max. heat

)

and 78°F

(

min. cool

)

(

22-26°C

)

; field

ustable lockin

levers; used with Q674L1561; used in

Y594C1322.

Y594C1322a

C1653 70 Obsolete. Fiber

las Canada; °C scaleplate; no H1, H2,

or C1 anticipation; used with Q674S1000; used in

Y594C1348.

See OEM for

replacement.

C1661 99 Obsolete. McQua

o; part no. 61202401; °F/°C

scaleplate; includes momentar

stem switch position

with sprin

release; used with Q674C1363.

T874C1125/

Q674B1075a

Replacement has HEAT-OFF-

COOL s

stem switchin

; no

momentar

stem switch

position; no LEDs.

C1695 45 Obsolete. Miller lo

o; used with Q674B1000; used in

Y594C1355. T874C1018

C1703 45 Obsolete. Intertherm lo

o; used with Q674B1000; used

in Y594C1363. T874C1018

C1737 44 Obsolete. Hone

well lo

o; Carrier part no. HH621603. T874C1018

C1745 44 Obsolete. AAF/Sn

der General lo

o; part no.

4ELN7919. T874C1018

C1752 219 Obsolete. McQua

/Sn

der General lo

o; part no.

061202402; 12°F offset between H1 and H2; °F/°C

scaleplate; no C1 anticipation; used with Q674C1363.

T8611M2025

C1760 44 Bard lo

o. T874C1018

C1778 219 Obsolete. AAF/Sn

der General lo

o; part no.

066804405; 12°F offset between H1 and H2; °F/°C

scaleplate; no C1 anticipation; used with Q674C1363.

See OEM for

replacement.

C1794 53 Obsolete. Carrier lo

o; Canada; part no. HH07AT160-W;

Premier White® color; °C scaleplate; includes lockin

cover.

T874C1018 Set sta

e 1 heat anticipator for

total current draw of fan and

sta

e 1 heat primar

C1802 246 Obsolete. California Economizer lo

o; °F/°C scaleplate;

used with Q674G1005; used in Y594C1371. T874C1018

C1810 237 Obsolete. Hone

well lo

o; TRADELINE model; Premier

White® color; used with Q674B1547; used in

Y594C1389.

Y594C1389

C1844 238 Ener

ht lo

o; used with Q674F1592; used in

Y594C1413. Y594R1425 Jumper E-W2; s

stem switch:

EM.HT.-HEAT-OFF-COOL.

C1851 60 Obsolete. Whalen lo

o. T874C1018

C1869 219 McQua

o; part no. 0073318801 Premier White®

color; °F/°C scaleplate. See OEM for

replacement.

Table 8. T874 Cross Reference.

Model

Number Fig.

No. Description Trade Model

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—852

C1877 53 Obsolete. Hone

well lo

o; TRADELINE model; used

with Q674B1554; used in Y594C1421. Y594D1347 Jumper RC-RH; s

stem

switch: OFF-HEAT-AUTO-

COOL

T874D 2-sta

e heat, 2-sta

e cool.

D1009 166, 82 Obsolete. Hone

well lo

o; used with Q674F1337,

E1007; used in Y594D1222, D1339. T874D1165

D1017 44, 88 Obsolete. Hone

well lo

o; TRADELINE model; includes

Allen wrench and screws to lock cover; used with

Q674A-G and Q674E1155.

T874D1165

D1025 44 Obsolete. Westin

house lo

o; H1 anticipator factor

set

at 0.75A; H2 anticipator factor

set at 1.2A. T874D1165

D1033 44 Lennox lo

o; part no. 13F0601; °F/°C scaleplate. T874D1165 Replacement has °F

scaleplate.

D1041 53 York lo

o; part no. 2TH04701524A; used with

Q674B1125. T874D1165

D1058 44 Obsolete. Shi

er special. T874D1165

D1066 44 Obsolete. ITT lo

o. T874D1165

D1074 51, 53,

146 Carrier lo

o; part no. HH07AT172; used with

Q674F1030

(

HH93AZ174

)

, F1063

(

HH93AZ181

)

Q674B.

T874D1165aSet H1 anticipator for current

draw of fan and sta

e 1 heat

primar

D1082 44, 46,

48, 72 Trane lo

o; used with Q674B1018, C1009, B1075,

B1133; used in Y594D1024, D1040. T874D1165

D1090 44 Obsolete. Dunham-Bush lo

o. T874D1165

D1108 44 Obsolete. Westin

house lo

o. T874D1165

D1116 76, 89,

94 Obsolete. Comfortmaker lo

o; part no. 1505-682; °F/°C

scaleplate; used with Q674C1116, E1197, G1104. T874D1165 Replacement has °F

scaleplate.

D1124 44 Obsolete. Airtemp special. T874D1165

D1132 44 Hone

well lo

o; °C scaleplate. T874D1165 Replacement has °F

scaleplate.

D1140 44 Obsolete. Solaron special. T874D1165 Replacement has °F

scaleplate.

D1157 51, 53,

146 Carrier lo

o; part no. HH07AT172; °C scaleplate; used

with Q674B or Q674F1030, F1063. T874D1165aReplacement has °F

scaleplate; set H1 anticipator

for current draw of fan and

sta

e 1 heat primar

D1165 82 Hone

well lo

o; SUPER TRADELINE® model; includes

Allen wrench and screws to lock cover, field-ad

ustable

ran

e stops, field-ad

ustable lockin

levers.

T874D1165

D1173 51, 53 Trane lo

o; part no. BAY28X183; heat anticipator factor

set at 0.4A. T874D1165aSet H1 anticipator for current

draw of fan and sta

e 1 heat

primar

D1181 51, 53 Obsolete. General Electric lo

o; lockin

cover includes

Allen wrench and screws to lock cover and ran

e stops

set at 72°F

(

max. heat

)

and 78°F

(

min. cool

)

T874D1165aSet H1 anticipator for current

draw of fan and sta

e 1 heat

primar

D1199 44 Obsolete. Lennox lo

o; part no. 13F0701; °C scaleplate. T874D1165 Replacement has °F

scaleplate.

D1207 114 Obsolete. Lennox lo

o; part no. 24F5201; used with

Q674L1199 and C815A1013 or Q674L1389. T8611M2025

(

pro

rammable

)

Wirin

differences

(

old=new

)

V-VR=R, Y=W3, X=C, R=O,

M=Y, M2=Y2-W2, F=G;

umper Y2-W2; no outdoor

reset needed; use onl

one

stem transformer.

Table 8. T874 Cross Reference.

Model

Number Fig.

No. Description Trade Model

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

53 60-2485—8

D1215 44 Obsolete. Friedrich Climate Master lo

o; part no.

AT5415; °F/°C scaleplate. T874D1165 Replacement has °F

scaleplate.

D1223 44 Hone

well lo

o; Hone

well Canada TRADELINE model;

Celsius scale. T874D1165 Replacement has °F

scaleplate.

D1231 44 Obsolete. Hone

well lo

o; 12°F

(

7°C

)

differential

between H1 and H2. T874D1165 Replacement has 2°F

differential between H1 and

H2.

D1249 44 Obsolete. Fedders special. T874D1165

D1256 44 Obsolete. Climatrol special. T874D1165

D1264 107 Obsolete. Carrier Heat Pump S

stem Control lo

o; part

no. HH07AT173; used with Q674L1116

(

HH93AZ171

)

. See OEM for

replacement.

D1272 51, 53 Obsolete. Carrier lo

o; part no. HH07AT162-03; °C

scaleplate; used with Q674B. T874D1165aReplacement thermostat has

°F scaleplate; set H1

anticipator for current draw of

fan and sta

e 1 heat primar

D1280 44 Obsolete. Command-Aire lo

o. T874D1165

D1298 90, 232 Obsolete. Sin

er special; °C scaleplate; controls two

separate heat/cool circuits; used with Q674D or

Q674G1054, G1062.

See OEM for

replacement.

D1306 90, 186 Obsolete. Trane special; part no. 02005949; controls

two separate heat/cool circuits; used with Q674G1013. See OEM for

replacement.

D1314 44 Obsolete. McQua

o; part no. 02005941; 12°F

(

6.6°C

)

differential between H1 and H2. T874D1165 Replacement has °F

scaleplate; 2°F differential

between H1 and H2.

D1322 46 Obsolete. Amana lo

o; part no. D68535-03; used with

Q674B1075; used in Y594D1149. T874D1165

D1330 44 Obsolete. Trane lo

o; part no. 13080242; °C scaleplate. T874D1165 Replacement has °F

scaleplate.

D1355 44 Obsolete. Climate Control special; part no. 02005942;

°C scaleplate; 6°C

(

11°F

)

differential between H1 and

H2.

T874D1165 Replacement has 2°F

differential between H1 and

H2.

D1363 44 Obsolete. McQua

o; part no. 02005943; 12°F

(

6.6°C

)

differential between H1 and H2; 6°F

(

3.3°C

)

differential between C1 and C2.

T874D1165 Replacement has 2°F

differential between H1 and

H2; 2°F differential between

C1 and C2.

D1405 44 Obsolete. Trane lo

o; part no. 02005952; 12°F

(

6.6°C

)

differential between H1 and H2; 6°F

(

3.3°C

)

differential

between C1 and C2.

T874D1165 Replacement has 2°F

differential between H1 and

H2; 2°F differential between

C1 and C2.

D1413 44 Obsolete. Trane lo

o; part no. 02005956; 12°F

(

6.6°C

)

differential between H1 and H2. T874D1165 Replacement has 2°F

differential between H1 and

H2.

D1421 44 Obsolete. Climate Control special; part no. 02005938;

°C scaleplate. T874D1165 Replacement has °F

scaleplate.

D1439 90 McQua

o; part no. 02005935; used with

Q674G1096. T874D1165

D1447 90 Obsolete. Climate Control special; part no. 02005940;

°C scaleplate; used with Q674G1096. T874D1165 Replacement has °F

scaleplate.

D1454 51, 53 Obsolete. Carrier lo

o. T874D1165aSet H1 anticipator for current

draw of fan and sta

e 1 heat

primar

D1462 80 Obsolete. Fedders multi-lo

o; part no. THTX-220-A0HB,

88-58-00550-001; used with Q674E1205. T874D1165

Table 8. T874 Cross Reference.

Model

Number Fig.

No. Description Trade Model

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—854

D1470 44 Obsolete. York lo

o; part no. 2TH04701624A; includes

Allen wrench and screws to lock cover; °C scaleplate. T874D1165 Replacement has °F

scaleplate.

D1488 44 Obsolete. Risco special. T874D1165

D1496 44 Obsolete. Bor

Warner multi-lo

o; part no.

6TH04701524A; includes Allen wrench and screws to

lock cover.

T874D1165

D1504 82 York lo

o; part no. 025-23321-000; °C scaleplate; used

with Q674E1007; used in Y594D1180. T874D1165 Replacement has °F

scaleplate.

D1512 44 Hone

well lo

o; Heil Quaker part no. HQ712002HW. T874D1165

D1520 44 Obsolete. Bard lo

o; ad

ustable lever stops set 68°F

(

max. heat

)

and 78°F

(

min. cool

)

. T874D1165

D1538 44 Obsolete. McQua

o; part no. 02005937. T874D1165

D1553 44 Obsolete. Climate Control special; part no. 02005944;

°C scaleplate; 6°C differential between H1 and H2; 3°C

differential between C1 and C2.

T874D1165 Replacement has 2°F

differential between H1 and

H2; 2°F differential between

C1 and C2; replacement has

°F scaleplate.

D1561 44 Obsolete. General Electric lo

o; used with Q674 A-G. T874D1165

D1587 44 Obsolete. Stiles Four Seasons lo

o. T874D1165

D1595 139 Obsolete. Nepco lo

o; used with Q674F1394. T874D1165/

Q674B1018a

Replacement has HEAT-OFF-

COOL s

stem switchin

; no

LEDs.

D1603 44 Obsolete. Arcoaire lo

o. T874D1165

D1611 44 Obsolete. No lo

o; Friedrich part no. AT5411; °F/°C

scaleplate. T874D1165 Replacement has °F

scaleplate.

D1629 82 Obsolete. Reznor lo

o; °F/°C scaleplate; used with

Q674E1007; used in Y594D1248. T874D1165 Replacement has °F

scaleplate.

D1678 44 Obsolete. Hone

well lo

o; Saudi O

er special; °C

scaleplate; one setpoint lever; used with Q674A-K. T874D1165 Replacement has °F

scaleplate; separate heatin

and coolin

setpoint levers.

D1686 98 Obsolete. McQua

o; part no. 60685501; 8°F

(

4.4°C

)

differential between H1 and H2; 6°F

(

3.3°C

)

differential

between C1 and C2; used with Q674E1312.

T874D1165 Replacement has 2°F

differential between H1 and

H2; 2°F differential between

C1 and C2.

D1694 202 Obsolete. McQua

o; part no. 60685201; used with

Q674G1120. See OEM for

replacement.

D1702 44 Obsolete. McQua

o; part no. 60685101. T874D1165

D1710 44 Trane lo

o. T874D1165

D1728 44 York-Miraco lo

o. T874D1165

D1744 44 American Standard lo

o; heat anticipator factor

set at

0.4A. T874D1165

D1751 44 Obsolete. Goettl lo

o; part no. 372080; ran

e stops set

at 68°F

(

max. heatin

and 78°F

(

min. coolin

. T874D1165

D1769 82 Obsolete. Arcoaire lo

o; part no. 1506753; °F/°C

scaleplate; used with Q674E1346; used in Y594D1297. T874D1165 Replacement has °F

scaleplate.

D1777 44 Obsolete. Climate Control lo

o; part no. 65495806; °F/

°C scaleplate. T874D1165 Replacement has °F

scaleplate.

D1785 82 Obsolete. Comfortmaker lo

o; part no. 1505753; °F/°C

scaleplate; used with Q674E1346; used in Y594D1305. T874D1165 Replacement has °F

scaleplate.

D1793 44 Obsolete. McQua

o; part no. 65495805; °F/°C

scaleplate. T874D1165 Replacement has °F

scaleplate.

Table 8. T874 Cross Reference.

Model

Number Fig.

No. Description Trade Model

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

55 60-2485—8

D1801 45, 208 Trol-A-Temp b

Hone

well lo

o; H1 and H2 anticipators

set at 0.10A; used with Q674B1463, D1115. None See Trol-A-Temp for

replacement.

D1819 44 Marv Air Com Stat lo

o; part no. 50059; ad

ustable

intersta

e between H1 and H2 and between C1 and C2;

includes Allen wrench and screws to lock cover; field

ustable ran

e stops; °F/°C scaleplate.

T874D1165 Replacement has a 2°F fixed

intersta

e differential between

H1 and H2 and between C1

and C2; replacement has °F

scaleplate.

D1827 45, 208 Trol-A-Temp b

Hone

well lo

o; Premier White® color;

H1 and H2 heat anticipators set at 0.10A; used with

Q674B1471, D1123.

None See Trol-A-Temp.

D1843 45 Obsolete. Janitrol lo

o; Goodman part no. CHT 90-120;

used with Q674B1000; used in Y594D1321. T874D1165

D1850 44 Hone

well lo

o; Carrier part no. HH621606. T874D1165

D1868 44 Bard lo

o; part no. 8405-031; H1 and H2 heat

anticipators factor

set at 0.25A; 5°F intersta

differential between H1 and H2 and between C1 and C2;

includes Allen wrench and screws to lock cover; field

ustable ran

e stops.

T874D1165 Replacement has 2°F fixed

intersta

e differential between

H1 and H2 and between C1

and C2.

D1876 44 Obsolete. AAF/Sn

der General lo

o; part no.

4ELN6981A; °F/°C scaleplate. T874D1165 Replacement has °F

scaleplate.

D1892 44 Obsolete. Climate-Tel lo

o. T874D1165

D1918 224,

225 Obsolete. AAF/Sn

der General lo

o; °F/°C scaleplate;

no coolin

anticipation; used with Q674E1312, C1298;

66804407.

See OEM for

replacement.

D1926 226 Obsolete. AAF/Sn

der General lo

o; °F/°C scaleplate;

no coolin

anticipation; used with Q674G1120;

66804406.

See OEM for

replacement.

D1934 44 Bard lo

o. T874D1165

D1942 82 Hone

well lo

o; TRADELINE model; used with

Q674E1403; used in Y594D1347; desi

ned to replace

York part no. 2TH04701024.

Y594D1347a

D1959 44 Rheem part no. 41-21444-01. T874D1165

D1967 44 Obsolete. Desert Aire lo

o. T874D1165

D1975 224,

225 Obsolete. McQua

part no. 066816603; °F/°C

scaleplate; no coolin

anticipation. See OEM for

replacement.

D1983 226 Obsolete. McQua

part no. 066816602; °F/°C

scaleplate; no coolin

anticipation; used with

Q674G1120.

See OEM for

replacement.

D1991 51, 53 Carrier lo

o; Premier White® color; °C scaleplate. T874D1165aSet H1 anticipator for total

current draw of fan and sta

1 primar

; replacement has °F

scaleplate.

D2007 44 Ultra-Zone lo

o. T874D1165

D2023 44 Hone

well lo

o; TRADELINE model; Premier White®

color; °C scaleplate; includes lockin

cover; used with

Q674A-K.

T874D1165 Replacement has °F

scaleplate and is bei

D2031 82 Obsolete. Hone

well lo

o; no cover; used with

Q674E1049 and TG504A1025; used in Y594D1354. T874D1165 or

Y594D1354

D2049 45, 72,

55, 66,

184

Obsolete. Carrier Heat Pump S

stem Control lo

o; part

no. HH07AT236; °F/°C scaleplate; used with Q674B-D,

Q674G; used in Y594D.

T874D1165 Replacement has °F

scaleplate.

Table 8. T874 Cross Reference.

Model

Number Fig.

No. Description Trade Model

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—856

D2056 44 Obsolete. ComStat lo

o; part no. 50056; °F/°C

scaleplate; ad

ustable intersta

e on both heatin

and

coolin

; includes lockin

cover and field-ad

ustable

lockin

levers.

T874D1165 Replacement has °F

scaleplate and 2°F fixed

differential in heatin

and

coolin

D2064 53 Obsolete. Carrier Weathermaker; part no. HH07AT209;

sta

e 1 and 2 heat anticipator factor

set 0.1A; taupe

color; used with Q674E1445; used in Y594D1412.

T874D1165 Set sta

e 1 heat anticipator for

total current draw of fan and

sta

e 1 heat primar

Replacement is bei

D2072 53 Obsolete. Carrier Zone Perfect; part no. HH07AT208;

taupe color; used with Q674E1445; used in Y594D1420. T874D1165 Set sta

e 1 heat anticipator for

total current draw of fan and

sta

e 1 heat primar

Replacement is bei

D2080 139 Obsolete. H

droheat lo

o. T874D1165/

Q674B1018a

Replacement s

stem switch:

HEAT-OFF-COOL; no LEDs.

D2098 44 Obsolete. Hone

well lo

o; °F scaleplate; one setpoint

lever; used with Q674D1008; used in Y594D1438. T874D1165 Replacement has °F

scaleplate and two setpoint

levers

D2106 44 Obsolete. Hone

well lo

o; °C scaleplate; one setpoint

lever; used with Q674D1008; used in Y594D1446. T874D1165 Replacement has °F

scaleplate and two setpoint

levers.

D2114 44 Obsolete. Bard lo

o; °C scaleplate. T874D1165 Replacement has °F

scaleplate.

D2122 224,

225 Obsolete. McQua

T874D2023 Replacement has °C

scaleplate.

T874D1165 Replacement has °F

scaleplate.

D2130 226 Obsolete. McQua

See OEM for

replacement.

D2148 44 Obsolete. Dr

Aire S

stems lo

o; °F/°C scaleplate. T874D1165

D2155 139 H

droheat lo

o; Premier White® color; °F/°C scaleplate;

used with Q674F1634. T874D1165/

Q674B1018a

Replacement s

stem switch:

HEAT-OFF-COOL; no LEDs.

D2163 208 Obsolete. Amana lo

o; part no. P1217501F; °F/°C

scaleplate. T874D1165

D2171 44 Obsolete. Amana lo

o; part no. P1217701F; °F/°C

scaleplate. T874D1942

D2189 44 Armstron

o; part no. 01142A024; °F/°C scaleplate;

includes Air Ease insert. T874D1165

D2197 44 Liebert lo

o; part no. 138968P3; °F/°C scaleplate;

intersta

e differential between H1 and H2 and between

C1 and C2; includes Allen wrench and screws to lock

cover; field-ad

ustable lockin

levers.

T874D1165

D2205 44 Aaon lo

o; Premier White® color; °F/°C scaleplate. T874D1165

T874E 0-sta

e heat, 2-sta

e cool.

E1008 44 Obsolete. Hone

well lo

o. T874E1016

E1016 44 Hone

well lo

o; TRADELINE model; includes Allen

wrench and screws to lock cover; field-ad

ustable

lockin

levers.

T874E1016

E1024 44 Obsolete. Westin

house lo

o. T874E1016

E1032 44 Lennox lo

o; part no. 13F0901; °F/°C scaleplate. T874E1016 Replacement has °F

scaleplate.

E1040 72 Obsolete. Trane lo

o; used with Q674C1009; used in

Y594E1015. T874E1016

Table 8. T874 Cross Reference.

Model

Number Fig.

No. Description Trade Model

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

57 60-2485—8

E1081 44 Trane lo

o; part no. BAY28X186; °F/°C scaleplate. T874E1016 Replacement has °F

scaleplate.

E1099 44 Obsolete. Lennox lo

o; part no. 13F1001; °C scaleplate. T874E1016 Replacement has °F

scaleplate.

E1107 44 Hone

well lo

o; °C scaleplate. T874E1016 Replacement has °F

scaleplate.

E1123 44 Obsolete. Amana lo

o; part no. D68535-4. T874E1016

E1149 44 Obsolete. York lo

o; part no. 2TH04701724A. T874E1016

E1156 44 Obsolete. Bor

Warner multi-lo

o; part no.

6TH04701724A. T874E1016

E1164 44 Obsolete. E. A. Juffali & Bros. lo

o. T874E1016

E1206 44 Obsolete. Trane lo

o. T874E1016

E1230 44 Obsolete. Climar lo

o. T874E1016

T874F 2-sta

e heat, 0-sta

e cool.

F1007 44 Hone

well lo

o. T874F1015

F1015 44 Hone

well lo

o; TRADELINE model; includes Allen

wrench and screws to lock cover; field-ad

ustable

lockin

levers.

T874F1015

F1023 44 Obsolete. Lennox lo

o; part no. 13F1101. T874F1015

F1031 44 Obsolete. Hone

well lo

o; °C scaleplate; used with

40003440-001 wallplate; used in Y594F1022. T874F1015 Replacement has °F

scaleplate.

F1049 44 Obsolete. Lennox lo

o; °C scaleplate. T874F1015 Replacement has °F

scaleplate.

F1056 55,

66 Obsolete. Hone

well lo

o; sta

es 1 and 2 heat

electricall

isolated; used with Q674D1008. None

F1072 44 Obsolete. Wesco lo

o; heat anticipator factor

set at

0.8A. T874F1015

F1098 189 Obsolete. Lennox lo

o; used with Q674D1008 to control

an M839. T874F1015 Set H1 and H2 anticipators to

lowest settin

F1106 95 Obsolete. Oneida lo

o; part no. 30A0287-02; used with

Q674K1018 on combination wood and oil applications. T874F1155

F1114 44 Hone

well lo

o; Hone

well Canada TRADELINE model;

°C scaleplate; includes Allen wrench and screws to lock

cover; field-ad

ustable lockin

levers.

T874F1015 Replacement has °F

scaleplate.

F1122 62 Obsolete. Hone

well lo

o; two heat setpoint levers;

used with Q674B1307. T874F1015/

Q674D1040 Replacement has no LED.

F1130 72, 91 Obsolete. Reznor lo

o; °F/°C scaleplate; used with

Q674C, D, or G; used with Q674C1009, G1005; used in

Y594F1048.

T874F1015 Replacement has °F

scaleplate.

F1148 44 Obsolete. Trane lo

o; part no. THT 0584. T874F1015

F1155 95 Hone

well lo

o; used with Q674K1026 on combination

wood and oil applications. T874F1155

T874G Heat pump models; 2-sta

e heat, 1-sta

e cool;

1–sta

e chan

eover.

G1006 84, 155 Obsolete. Hone

well lo

o; used with Q674E1015. Y594G1252aWirin

differences

(

old=new

)

R=O, M=Y, F=G, V=R, Y=W2;

E-W2

umper re

uired.

Table 8. T874 Cross Reference.

Model

Number Fig.

No. Description Trade Model

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—858

G1014 86, 150 Obsolete. Lennox lo

o; part no. 24F5801; °F/°C

scaleplate; H2 anticipator factor

set at 0.25A for fast

cle performance; chan

eover in coolin

mode;

independent heatin

and coolin

circuits; used with

Q674E1148, F1113.

Y594G1252aWirin

differences

(

old=new

)

R=O, M=Y, F=G, Y=W2,

V-VR=R

(

must use sin

transformer

)

G1022 86, 150 Obsolete. Lennox lo

o; part no. 24F5701; °F/°C

scaleplate; H2 anticipator factor

set at 0.25A for fast

cle performance; chan

eover in coolin

mode;

independent heatin

and coolin

circuits; used with

Q674E1148, F1113.

Y594G1252aWirin

differences

(

old=new

)

R=O, M=Y, F=G, Y=W2,

V-VR=R

(

must use sin

transformer

)

G1048 153,

159 Obsolete. Westin

house lo

o; H2 anticipator factor

set

at 1.2A; used with Q674F1121, J1019. Y594G1252aWirin

differences when

replacin

T874G/Q674J1019

(

old=new

)

: W=W2.

G1055 161 Carrier Heat Pump S

stem Control lo

o; part no.

HH07AT171; H2 anticipator factor

set at 0.8A;

chan

eover in coolin

mode; used with Q674J1035

(

HH93AZ173

)

None See subbase description for

replacement information.

G1071 50, 103,

126,

183

Obsolete. Carrier Heat Pump S

stem Control lo

meets DoD specifications; H2 anticipator factor

set at

0.8A; used with Q674P1005

(

HH93AZ169

)

, L1041

(

HH93AZ175

)

, B1158, or J1050.

Y594G1419 Wirin

differences

(

old=new

)

C=X;

umper Y1-W1.

G1089 154 Obsolete. Marvair lo

o; special for Crispaire; H2

anticipator factor

set at 1.2A; used with Q674F1204;

used in Y594G1153.

Y594G1393aWirin

differences

(

old=new

)

A=L.

G1097 155 Obsolete. Hone

well lo

o; Rheem part no. ZXMT-B79;

used with Q674F1238

(

41-20797-14

)

. Y594G1252a

G1105 153 Obsolete. Heat Wave

(

Southwest Mf

)

o; H2

anticipator factor

set at 1.2A; used with Q674F1170. Y594G1252a

G1113 103 Obsolete. Carrier Heat Pump S

stem Control lo

meets DoD specifications; H2 anticipator factor

set at

0.8A; used with Q674L1041.

Y594G1419aWirin

differences

(

old=new

)

C=X;

umper Y1 -W1.

G1121 103 Obsolete. Carrier Heat Pump S

stem Control lo

o; part

no. HH07AT161; °C scaleplate; H2 anticipator factor

set at 0.8A; includes Allen wrench and screws to lock

cover.

Y594G1419aWirin

differences

(

old=new

)

C=X;

umper Y1-W1.

G1139 143,

234 Obsolete. Hone

well lo

o; used with Q674B1240,

C1108. None See subbase description for

replacement information.

G1147 148 Obsolete. Hone

well lo

o; chan

eover in coolin

mode;

used with Q674F1139. Y594G1252aWirin

differences

(

old=new

)

C=X.

G1154 84, 139 Obsolete. Lennox lo

o; used with Q674E1015, F1105. Y594G1252aSee subbase description for

replacement information.

G1162 155 Obsolete. Lennox lo

o; meets DoD specifications; used

with Q674F. Y594G1419aW1-Y1

umper re

uired.

G1170 160 Obsolete. York lo

o; part no. 2TH11702424A; H2

anticipator is fixed; used with Q674J1027; used in

Y594G1013.

Y594G1567a

G1188 147 Obsolete. Hone

well lo

o; Keeprite/Westin

house

special; H2 anticipator factor

set 1.2A; °C scaleplate;

chan

eover in coolin

mode; used with Q674F1295.

Y594G1252aWirin

differences

(

old=new

)

S=L.

G1196 160 Obsolete. York lo

o; °C scaleplate; chan

eover in

coolin

mode; used with Q674J1027; used in

Y594G1138.

Y594G1567a

Table 8. T874 Cross Reference.

Model

Number Fig.

No. Description Trade Model

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

59 60-2485—8

G1204 162 Hone

well lo

o; desi

ned for use on Trane heat pumps;

no H2 anticipation; chan

eover in coolin

mode; used

with Q674J1043 and C815A1005; used in Y594G1161.

Y594G1161aDesi

ned for use on Trane

heat pumps.

G1212 155 Obsolete. Hone

well lo

o; H2 anticipator factor

set at

0.2A; chan

eover in coolin

mode; includes shunt to

pass H2 anticipator with W3 heat rela

s; used with

Q674F1238.

Y594G1252a

G1220 235 Obsolete. Rheem lo

o; part no. RXMT-C71; chan

eover

in coolin

mode; used with Q674F1238. Y594G1252a

G1238 155 Obsolete. Ruud lo

o; part no. UXMT-C71; chan

eover

in coolin

mode; used with Q674F1238. Y594G1252a

G1246 Obsolete. Hone

well lo

o; chan

eover in coolin

mode.

155 Used with Q674F1212; used in Y594G1195, G1252,

G1369. Y594G1252a

170 Used with Q674F1410; used in Y594G1393. Y594G1393a

G1261 58, 157 Obsolete. Bor

-Warner; used with Q674D1032, F1253. None See subbase description for

replacement information.

G1279 58, 157 Obsolete. Br

ant lo

o; used with Q674D1032, F1253. None See subbase description for

replacement information.

G1287 58, 157 Obsolete. Wesco lo

o; used with Q674D1032, F1253. None See subbase description for

replacement information.

G1295 58 Obsolete. York lo

o; part no. 2TH11702724A; used with

Q674D1032. T874D1165/

Q674D1040 Wirin

differences

(

old=new

)

Y=Y2, O=Y1, W=W2;

umper

W1-Y2.

G1345 160 Obsolete. York lo

o; part no. 2TH11702624A; °C

scaleplate; used with Q674J1027. Y594G1575a

G1352 73 Obsolete. Command-Aire lo

o; 12°F differential

between H1 and H2 for ni

ht setback; used with

Q674C1066.

Y594H1012aWirin

differences

(

old=new

)

Y1=O, Y2=Y, L=R, R=none; R-

umper re

uired; no ni

setback.

T8600D1004

(

pro

rammable

)

Wirin

differences

(

old=new

)

Y1=O, Y2=Y, L=RH; RC-RH

umper re

uired; includes

ht setback.

G1378 79 Obsolete. Mammoth lo

o; H2 anticipator factor

set at

0.8A; 12°F differential between H1 and H2 for ni

setback; °F/°C scaleplate; used with Q674C1124; used

in Y594G1294.

Y594H1012aWirin

differences

(

old=new

)

R1=none, R2=L; R-L

umper

uired; no ni

ht setback.

T8090A1007/

Q682A1038a

(

pro

rammable

)

Includes ni

ht setback; W-Y

umper re

uired.

G1402 129 Obsolete. York part no. 2TH11702824A; meets DoD

specifications; used with Q674L1363. Y594R1425aWirin

differences

(

old=new

)

W=W2, X=E, B=X;

umper

Y-W1.

G1410 155 Obsolete. Bor

-Warner multi-lo

o; part

no. 6TH11703024A; used with Q674F1311. T874G1246a or

Y594G1252a

G1428 160 Obsolete. Bor

-Warner multi-lo

o; part no.

6TH11702424A; used with Q674J1027; used in

Y594G1229.

Y594G1567a

G1436 58 Obsolete. Bor

-Warner multi-lo

o; part no.

6TH11702724A. T874D1165/

Q674D1040 Wirin

differences

(

old=new

)

Y=Y2, O=Y1, W=W2;

umper

W1-Y2.

Table 8. T874 Cross Reference.

Model

Number Fig.

No. Description Trade Model

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—860

G1444 160 Obsolete. ROCA lo

o; °C scaleplate; used with

Q674J1027. Y594G1567a Replacement has °F

scaleplate.

G1451 155 Obsolete. BDP multi-lo

o; part no. HH641502; used with

Q674F1212; used in Y594G1245. T874G1246a or

V594G1252a

G1469 194 Obsolete. No lo

o; Addison special; used with

Q674F1345; used in Y594G1344. Y594G1252aWirin

differences

(

old=new

)

Y1=O, C=X, W1=Y1, X=L.

G1485 163 Obsolete. AAF lo

o; part no. 4ELN-7839; °F/°C

scaleplate; 10°F differential between H1 and H2 for ni

setback and momentar

RESET s

stem switch position;

used with Q674C1199.

Y594G1393aNo ni

ht setback or

momentar

reset switch.

T8611G1004

(

pro

rammable

)

Includes ni

ht setback; no

momentar

reset switch.

G1493 167 Obsolete. Hone

well lo

o; Rheem part no. 41-20797-

18; used with Q674F1360. Y594G1526a

G1501 195 Obsolete. Coleman lo

o; part no. 3600-375; chan

eover

in coolin

mode; used with Q674F1378. Y594G1252aWirin

differences

(

old=new

)

L1=L; chan

eover in coolin

onl

G1535 163 Obsolete. AAF/Sn

der General lo

o; 4ELN7839 °F/°C

scaleplate; 10°F differential between H1 and H2 for ni

setback and momentar

RESET s

stem switch position;

used with Q674C1199.

Y594G1393aNo ni

ht setback or

momentar

reset switch.

T8611G1004

(

pro

rammable

)

Includes ni

ht setback.

G1543 194 Obsolete. Addison lo

o; Weather Kin

part no. 8403-

197; used with Q674F1345; used in Y594G1328. Y594G1252aWirin

differences

(

old=new

)

Y1=O, C=X, W1=Y, X=L.

G1568 160 Obsolete. Luxaire lo

o; part no. 026-00068-000; °C

scaleplate; used with Q674J1126; used in Y594G1351. Y594G1367aReplacement has °F

scaleplate.

G1576 169 Obsolete. Coleman lo

o; part no. 3600-373; chan

eover

in heatin

and coolin

mode; used with Q674F1402;

used in Y594G1377.

Y594G1633a

G1584 73 Obsolete. No lo

o; Friedrich part no. AT5784; 8°F

(

4.4°C

)

differential between H1 and H2; used with

Q674C1223.

Y594H1012aWirin

differences

(

old=new

)

Y1=O, Y2=Y, L=R, R=none;

L-R

umper re

uired; no ni

setback.

T8611G1004

(

pro

rammable

)

Includes ni

ht setback.

G1592 155 Obsolete. Arcoaire lo

o; used with Q674F1212; used in

Y594G1385. T874G1246a or

Y594G1252a

G1600 199 Obsolete. Hone

well lo

o; meets DoD specifications;

used with Q674F1428; used in Y594G1401. Y594G1419a Wirin

differences

(

old=new

)

umper W1-Y1.

G1618 73 Obsolete. Hone

well lo

o; 12°F differential between H1

and H2 for ni

ht setback; used with Q674C1256. Y594H1012aWirin

differences

(

old=new

)

Y1=O, Y2=Y, L=R, R=none;

L-R

umper re

uired; no ni

setback.

T8600C1162

(

pro

rammable

)

Wirin

differences

(

old=new

)

L=R, W=O; W-Y

umper

uired; includes ni

setback.

G1626 167 Hone

well lo

o; used with Q674F1436; used in

Y594G1526. None

G1642 227 Hone

well lo

o; TRADELINE model; meets DoD

specifications; used with Q674F1444; used in

Y594G1419.

Y594G1419a

Table 8. T874 Cross Reference.

Model

Number Fig.

No. Description Trade Model

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

61 60-2485—8

G1659 177 Obsolete. Mammoth lo

o; 0.8A maximum current

throu

h B or O terminal; 12°F differential between H1

and H2 for ni

ht setback; used with Q674C1330; used in

Y594G1427.

Y594H1012aWirin

differences

(

old=new

)

R2=L, R1=none; L-R

umper

uired; no ni

ht setback.

T8611G1004

(

pro

rammable

)

Includes ni

ht setback.

G1675 174 Obsolete. American Standard lo

o; part no.

ASYSTAT650; used with Q674J1142; used in

Y594G1443.

Y594G1161a

G1691 176 Obsolete. Command Aire lo

o; part no. P1013-0060;

12°F

(

6.6°C

)

differential between H1 and H2 for ni

setback; used with Q674C1389, C1397.

Y594H1012aWirin

differences

(

old=new

)

Y1=O, Y2=Y, R=none; L-R

umper re

uired; no ni

setback.

T8611G1004

(

pro

rammable

)

Includes ni

ht setback.

G1717 175 Obsolete. Carrier Heat Pump S

stem Control lo

o; part

no. HH07AT102N; used with Q674J1167; used in

Y507J1201.

Y594G1252aWirin

differences

(

old=new

)

C=X, D=L; replacement has

AUX. HEAT and EM. HEAT

LEDs.

G1741 227 Hone

well lo

o; TRADELINE model; includes factor

set ran

e stops at 68°F

(

max. heat

)

and 78°F

(

min.

cool

)

; Premier White® color; used with Q674F1477;

used in Y594G1476.

Y594G1476a

G1758 211 Trol-A-Temp b

Hone

well lo

o; Premier White® color;

chan

eover is provided b

Trol-A-Temp zone panel;

used with Q674F1485; used in Y594G1492.

None See Trol-A-Temp for

replacement.

G1774 216 Obsolete. Comfortmaker lo

o; part no. 1505756; used

with Q674J1175; used in Y594G1500. Y594G1252aWirin

differences

(

old=new

)

E=W2, W1=W3, X=E, C=X.

G1782 216 Obsolete. Arcoaire lo

o; part no. 1506756; used with

Q674J1175; used in Y594G1518. Y594G1252aWirin

differences

(

old=new

)

E=W2, W1=W3, X=E, C=X.

G1790 161 Obsolete. Carrier lo

o; Premier White® color; °C

scaleplate; includes Allen wrench and screws to lock

cover; used with Q674J1191.

Y594G1252aWirin

differences

(

old=new

)

C=X; replacement has °F

scaleplate.

G1816 163 Climate Master lo

o; part no. AT5716; °F/°C scaleplate;

10°F differential between H1 and H2 and momentar

RESET s

stem switch position.

Y594G1393aNo momentar

reset switch.

G1824 227 Hone

well lo

o; Australian TRADELINE model; Premier

White® color; °C scaleplate; used with Q674F1477;

used in Y594G1534.

Y594G1476a

G1832 231 Obsolete. Intertherm lo

o; used with Q674F1519; used

in Y594G1542. Y594G1252aReplacement has auto

chan

eover in coolin

mode

onl

G1840 231 Obsolete. Miller lo

o; used with Q674F1519; used in

Y594G1559. Y594G1252aReplacement has auto

chan

eover in coolin

mode

onl

G1857 229 Obsolete. Lennox lo

o; °C scaleplate; Premier White®

color; used with Q674F1535; used in Y594G1583. Y594G1161aWirin

differences

(

old=new

)

E=X2, C=B, L=F.

G1865 160 Hone

well lo

o; TRADELINE model; desi

ned to

replace Y594G1013

(

York part no. 2TH11702424

)

Y594G1229

(

York part no. 6TH11702424

)

, and York part

no. 2TH117704124

)

; used with Q674J1209; used in

Y594G1567.

Y594G1567a

Table 8. T874 Cross Reference.

Model

Number Fig.

No. Description Trade Model

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—862

G1873 160 Obsolete. Hone

well lo

o; TRADELINE model; Premier

White® color; desi

ned to replace Y594G1013

(

York

part no. 2TH11702424

)

, Y594G1229

(

York part no.

6TH11702424

)

, and York part no. 2TH117704124

)

; used

with Q674J1225; used in Y594G1575.

Y594G1567aReplacement is bei

G1881 167 Rheem; part no. 41-20797-18. Y594G1526a

G1899 169 Obsolete. Amana; part no. 10574101; used with

Q674F1550; used in Y594G1591. Y594G1633a

G1915 155 Econar lo

o; used with Q674F1212; used in

Y594G1609. Y594G1252a

170 Used with Q674F1410. Y594G1393a

G1923 176 Trane lo

o; part no. X13510599010; H2 make 12°F

below H1 make. Y594H1012aWirin

differences

(

old=new

)

Y1=O, Y2=Y, R=none; L-R

umper re

uired; no ni

setback.

T8611G1004

(

pro

rammable

)

Includes ni

ht setback.

G1931 155,

170 Obsolete. Hone

well lo

o; Premier White® color; °C

scaleplate; used with Q674F1568. None See subbase description for

replacement information.

G1949 73 Obsolete. Carrier Heat Pump S

stem Control lo

o; part

no. HH07AT204; °F/°C scaleplate; H2 make 8°F below

H1 make; used in Y594.

Y594H1012aWirin

differences

(

old=new

)

Y1=O, Y2=Y, L=R, R=none; R-

umper re

uired; no ni

setback.

T8600D1004

(

pro

rammable

)

Wirin

differences

(

old=new

)

Y1=O, Y2=Y, L=RH; RC-RH

umper re

uired; includes

ht setback.

G1956 30, 103,

126,

183

Obsolete. Carrier lo

o; Canada; Premier White® color;

°C scaleplate; includes lockin

cover. Y594G1476 Replacement has °F

scaleplate.

G1964 160 York lo

o; Canada; Premier White® color; °C scaleplate;

used in Y594G1625. Y594G1575aReplacement has °F

scaleplate.

G1972 169 Hone

well lo

o; TRADELINE model; used with

Q674F1584; used in Y594G1633. Y594G1633a

G1980 169 Obsolete. Amana lo

o; part no. 10574103; used with

Q674F1600; used in Y594G1641. Y594G1633aWirin

differences

(

old=new

)

W3=W2.

G1998 155 Obsolete. Tempstar lo

(

Inter-Cit

Products

)

; used in

Y594G1658; used with Q674F1212. Y594G1252a

G2004 103 Hone

well lo

o; TRADELINE model; used with Q674L;

used in Y594G. Y594G1666

161 Used with Q674J1274; used in Y594G1674. Y594G1674

G2046 155,

170 WaterFurnace lo

o; part no. TA21H03; Premier White®

color; °F/°C scaleplate; used with Q674F1667; used in

Y594G1716.

Y594G1716

T874H Heat pump model; 1-sta

e heat, 1-sta

e cool,

1-sta

e chan

eover in cool.

H1005 74 Obsolete. Command Aire lo

o; used with Q674C1041. Y594H1012aWirin

differences

(

old=new

)

Y1=O, Y2=Y; L-R

umper

uired.

H1013 74 Obsolete. Friedrich part no. AT5813; °C scaleplate; used

with Q674C1041. Y594H1012aWirin

differences

(

old=new

)

Y1=O, Y2=Y; L-R

umper

uired; replacement has °F

scaleplate.

Table 8. T874 Cross Reference.

Model

Number Fig.

No. Description Trade Model

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

63 60-2485—8

H1021 74 Obsolete. Friedrich Climate Master lo

o; part no.

AT5821; °F/°C scaleplate; used with Q674C1041. Y594H1012aWirin

differences

(

old=new

)

Y1=O, Y2=Y; L-R

umper

uired; replacement has °F

scaleplate.

H1039 79 Obsolete. Mammoth lo

o; °F/°C scaleplate; used with

Q674C1124; used in Y594H1004. Y594H1012aWirin

differences

(

old=new

)

R1=R, R2=L.

H1054 74 Obsolete. No lo

o; Friedrich part no. AT5854; used with

Q674C1041. Y594H1012aWirin

differences

(

old=new

)

Y1=O, Y2=Y; L-R

umper

uired.

H1062 164 Hone

well lo

o; used with Q674C1249; used in

Y594H1012. Y594H1012a

H1070 172,

173 Obsolete. Carrier Heat Pump S

stem Control lo

o; part

no. HH07AT166; °C scaleplate; used with Q674B1406

(

HH93AZ200

)

or Q674C1322

(

HH93AZ199

)

None See subbase description for

replacement information.

H1088 172,

173 Obsolete. Carrier Heat Pump S

stem Control lo

o; part

no. HH07AT167; used with Q674B1406

(

HH93AZ200

)

or Q674C1322

(

HH93AZ199

)

None See subbase description for

replacement information.

H1096 177 Obsolete. Mammoth Water Source Heat Pump lo

o; °F/

°C scaleplate; chan

eover sta

e 0.8A maximum; used B

or O terminal; used with Q674C1330.

Y594H1012aWirin

differences

(

old=new

)

R1=R, R2=L; L-R

umper

uired.

H1112 74 No lo

o; Friedrich part no. AT5812; used with

Q674C1355. Y594H1012aWirin

differences

(

old=new

)

Y1=O, Y2=Y; L-R

umper

uired.

H1120 205 Obsolete. Command Aire lo

o; part no. P1013-0055;

used with Q674C1389, C1397. Y594H1012aWirin

differences

(

old=new

)

Y1=O, Y2=Y.

H1138 221 Obsolete. Climate Master lo

o; part no. AT5838; used

with Q674C1470. Y594H1012aWirin

differences

(

old=new

)

Y1=O, Y2=Y; replacement has

MALFUNCTION LED onl

H1146 205 Trane lo

o; part no. X13510598010. Y594H1012aWirin

differences

(

old=new

)

Y1=O, Y2=Y.

H1153 173 Obsolete. Carrier Heat Pump S

stem Control lo

o; part

no. HH07AT167; °F/°C scaleplate; used with

Q674C1322; used in Y594H1053.

None See subbase description for

replacement information.

H1161 74 Obsolete. Carrier Heat Pump S

stem Control lo

o; part

no. HH07AT203; °F/°C scaleplate; used with

Q674C1496; used in Y594H1038.

Y594H1012aWirin

differences

(

old=new

)

Y1=O, Y2=Y; L-R

umper

uired.

T874J Heat pump model. 2-sta

e heat, 1-sta

e cool.

J1002 124,

144,

206,

207

Obsolete. Carrier Heat Pump S

stem Control lo

o; part

no. HH07AT175; used with Q674J1068

(

HH93AZ183

)

Q674J1159

(

HH93AZ196

)

, Q674L1074

(

HH93AZ186

)

Q674L1637

(

HH93AZ195

)

None See subbase description for

replacement information.

J1010 124,

171 Obsolete. BDP multi lo

o; part no. 34427DP124/P272-

2471; used with Q674J1084, L1371. None See subbase description for

replacement information.

J1028 124,

144,

206,

207

Obsolete. Carrier Heat Pump S

stem Control lo

o; part

no. HH07AT165; °C scaleplate; used with Q674J1068

(

HH93AZ183

)

, Q674J1159

(

HH93AZ196

)

, Q674L1074

(

HH93AZ186

)

, Q674L1637

(

HH93AZ195

)

None See subbase description for

replacement information.

J1036 124,

171 Obsolete. Miller lo

o; part no. 9132230; used with

Q674J1217. T8511G1021

J1044 124,

171 Obsolete. Intertherm lo

o; part no. 9132240; used with

Q674J1217. T8511G1021

J1051 124,

144 Obsolete. Carrier lo

o; part no. HH07AT165-W; Premier

White® color; °C scaleplate. None See subbase description for

replacement information.

Table 8. T874 Cross Reference.

Model

Number Fig.

No. Description Trade Model

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—864

J1069 124,

144,

206,

207

Obsolete. Hone

well lo

o; TRADELINE model; used

with Q674J1282; used in Y594J1019. T8511G1021

J1077 124,

171 Obsolete. Nord

ne lo

o; part no. 9148300; °F/°C

scaleplate. T8511G1021

T874K Heat pump model; 2-sta

e heat, 1-sta

e cool, automatic

chan

eover in heat.

K1001 77 Obsolete. LSI Mammoth lo

o; used with Q674C1090. Y594G1419aWirin

differences

(

old=new

)

RH-RC=R, W1=B, W3=W2,

W2=W1; remove Y1-W1

umper.

K1019 181 Obsolete. McQua

/Sn

der General lo

o; part no.

60687301; °F/°C scaleplate; H1 anticipator set at 0.83A;

8°F intersta

e differential between H1 and H2 for ni

setback; used with Q674C1280.

Y594G1252aWirin

differences

(

old=new

)

C=X, W=B, A=L;

umper

E-W2; no ni

ht setback.

T8611G1004

(

pro

rammable

)

Wirin

differences

(

old=new

)

C=X, W=B, A=X2;

umper X2-

R; remove external time clock;

includes ni

ht setback.

K1027 181 Obsolete. AAF/Sn

der General lo

o; part no.

066804403; °F/°C scaleplate; H1 anticipator set at

0.83A; 8°F intersta

e differential between H1 and H2 for

ht setback; used with Q674C1280.

Y594G1252aWirin

differences

(

old=new

)

C=X, W=B, A=L;

umper

E-W2; no ni

ht setback.

T8611G1004

(

pro

rammable

)

Wirin

differences

(

old=new

)

C=X, W=B, A=X2;

umper

X2-R; remove external time

clock; includes ni

ht setback.

T874L Heat pump model; 2-sta

e heat, 1-sta

e cool,

chan

eover in cool.

L1000 198 Obsolete. Carrier lo

o; part no. HH07AT176; used with

Q674E1270

(

HH93AZ189

)

. Y594G1419aE-W2

umper re

uired.

L1018 138,

165 Obsolete. Carrier Multiplex S

stem lo

o; part no.

HH07AT178; used with Q674B1356

(

HH93AZ192

)

Q674C1264

(

HH93AZ193

)

See OEM for

replacement.

L1026 198 Obsolete. Hone

well lo

o; BDP part no. P272-2786;

used with Q674E1304. Y594G1419aE-W2

umper re

uired.

L1034 203 Obsolete. McQua

o; part no. 60687201; °F/°C

scaleplate; H1 anticipator factor

set at 0.83A; used with

Q674C1280.

Y594G1419aWirin

differences

(

old=new

)

Y=Y1, W=B, A=X1; remove

Y1-W1

umper.

L1059 215,

213 Obsolete. Carrier lo

o; part no. HH07AT192; used with

Q674B1448

(

HH93A2202

)

or Q674C1413

(

HH93AZ204

)

See OEM for

replacement.

L1067 203 Obsolete. AAF/Sn

der General lo

o; part no.

066804402; H1 anticipator factor

set at 0.83A; used

with Q674C1280.

Y594G1419a Wirin

differences

(

old=new

)

Y=Y1, W=B, A=X1; remove

Y1-W1

umper.

L1075 203 Obsolete. McQua

o; part no. 073318601; Premier

White® color; °F/°C scaleplate; includes AAF insert. See OEM for

replacement.

T874N Heat pump model; 2-sta

e heat; 1-sta

e cool plus

chan

eover; chan

eover in heat mode.

N1008 178 Obsolete. Williamson lo

o; used with Q674F1196; used

in Y594N1007. T874N1016

N1016 178 Hone

well Heat Pump Thermostat lo

o; used with

Q674F1220. T874N1016

N1024 179,

217 Bard lo

o; H1 and C1 anticipation fixed; used with

Q674F1261. None See subbase description for

replacement information.

Table 8. T874 Cross Reference.

Model

Number Fig.

No. Description Trade Model

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

65 60-2485—8

N1040 179 Obsolete. Hone

well lo

o; H1 and C1 anticipation fixed;

used with Q674F1261; used in Y594N1015. None

N1057 178 Obsolete. Intertherm lo

o; part no. 9111882; used with

Q674F1220; used in Y594N1023. T874N1016

N1065 178 Obsolete. Miller lo

o; Nord

ne part no. 9122240; used

with Q674F1220; used in Y594N1031. T874N1016

T874P Heat pump model; 2-sta

e heat, 1-sta

e cool, automatic

chan

eover in cool.

P1006 57, 78 Obsolete. McQua

o; part no. 860-442725B-00; 8°F

(

4.4°C

)

intersta

e differential between H1 and H2; used

with Q674B1273, C1140.

None See subbase description for

replacement information.

P1014 78 Obsolete. Friedrich/Climate Master lo

o; °F/°C

scaleplate; 8°F

(

4.4°C

)

differential between H1 and H2

for ni

ht setback; used with Q674C1207.

T8600D2028

(

pro

rammable

)

Wirin

differences

(

old=new

)

L=R, W=O; W-Y

umper

uired; includes ni

setback.

P1022 97 Obsolete. Friedrich/Climate Master lo

o; part no.

AT5922; °F/°C scaleplate; 8°F

(

4.4°C

)

differential

between H1 and H2 for ni

ht setback; used with

Q674C1215.

None See subbase description for

replacement information.

P1030 97 Obsolete. No lo

o; Friedrich part no. AT5930; 8°F

(

4.4°C

)

differential between H1 and H2 for ni

ht setback;

used with Q674C1215.

None See subbase description for

replacement information.

P1055 68, 97 Obsolete. Carrier Heat Pump S

stem Control lo

o; part

no. HH07AT205; °F/°C scaleplate; heat intersta

differential 8°F

(

4.4°C

)

None See subbase description for

replacement information.

T874Q 1-sta

e heat; used with another T874 for ni

ht setback.

Q1005 44 Hone

well lo

o. T874A1036

Q1013 44 Obsolete. Lennox lo

o; part no. 13F1201; °F/°C

scaleplate. T874A1036 Replacement has °F

scaleplate.

Q1021 44 Obsolete. Lennox lo

o; part no. 13F1301; °C scaleplate. T874A1036 Replacement has °F

scaleplate.

T874R Heat pump model; 2-sta

e heat, 1-sta

e cool, manual

chan

eover.

R1004 47 Obsolete. Hone

well lo

o; used with Q674B1042; used

in Y594R1029. Y594R1243aWirin

differences

(

old=new

)

W1=W2.

R1012 47 Obsolete. Hone

well lo

o; Addison heat pump; used

with Q674B1109. Y594R1243aWirin

differences

(

old=new

)

W1=W2.

R1020 102 Obsolete. Lennox lo

o; part no. 24F5401; °F/°C

scaleplate; H1 and C1 anticipators are fixed; auxiliar

heat circuit powered b

separate transformer; used with

Q674L1025.

Y594R1243a Wirin

differences

(

old=new

)

M=Y, F=G, V-VR=R, Y=W2,

R=O; replacement has °F

scaleplate.

R1038 102 Obsolete. Lennox lo

o; °C scaleplate; H1 and C1

anticipators are fixed; auxiliar

heat circuit powered b

separate transformer; used with Q674L1025.

Y594R1243aWirin

differences

(

old=new

)

M=Y, F=G, V-VR=R, Y=W2,

R=O; replacement has °F

scaleplate.

R1046 120,

101 Obsolete. York lo

o; part no. 2TH11702224A; H2

anticipator is fixed; used with Q674L1272 in Y594R1011

or with Q674L1094.

Y594R1664a

R1053 109 Obsolete. Hone

well lo

o; H2 anticipator is fixed; used

with Q674L1140; used in Y594R1136. Y594R1763aDesi

ned for use on Trane

heat pumps.

R1061 104 Obsolete. Hone

well lo

o; H2 anticipator is field

ustable; chan

eover in coolin

; used with

Q674L1082.

Y594R1243aReplacement has auto fan in

Emer

enc

Heat mode.

Table 8. T874 Cross Reference.

Model

Number Fig.

No. Description Trade Model

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—866

R1079 123 Obsolete. Ruud lo

o; part no. UXMT-C70; used with

Q674L1157. Y594R1243a

R1087 120 Obsolete. Hone

well lo

o; Special for Dunham Bush;

use with Q674L. Y594R1664a

R1095 123 Obsolete. Rheem lo

o; part no. RXMT-C70; used with

Q674L1157. T874R1152/

Y594R1243a

R1103 104 Obsolete. Westin

house lo

o; used with Q674L. Y594R1243a

R1111 116,

104 Obsolete. Marvair lo

o; H2 anticipator factor

set at

1.2A; used with Q674L1215, L1082; used in

Y594R1128.

Y594R1243aReplacement has auto fan in

Emer

enc

Heat mode.

R1129 113 Bard lo

o; used with Q674L1181. Y594R1243aWirin

differences

(

old=new

)

X1=X.

R1137 108,

125 Obsolete. Hone

well lo

o; Heil Quaker part no.

HQ711597HW; used with Q674L1132; used in

Y594R1110.

Y594R1292a

R1145 120 Obsolete. York lo

o; °C scaleplate; H2 anticipator is

fixed; used with Q674L1272; used in Y594R1102. Y594R1664a

R1152 115 Hone

well lo

o; used with Q674L1207, L1033; used in

Y594R1243. Y594R1243a

R1160 182 Obsolete. Hone

well Advanced Heat Pump S

stem

o; used with Q674L1298 and W89. None

R1178 110,

111 Obsolete. Lennox lo

o; part no. 24F5601; °F/°C

scaleplate; auxiliar

heat circuit powered b

separate

transformer; fast c

cle sta

e H2 anticipator; re

uires

outdoor reset and independent circuits; used with

Q674L1165, L1355.

Y594R1763aWirin

differences

(

old=new

)

V-VR=R, M=Y, F=G, X=B,

Y=W, A=T, R=O, E=X2.

R1186 182 Obsolete. Hone

well Advanced Heat Pump S

stem

o; used with Q674L1231 and W89. None

R1194 115 Obsolete. Amana lo

o; used with Q674L1249 and W89. Y594R1243a

R1202 201 Obsolete. Intertherm lo

o; part no. 9111871; used with

Q674L1264 or Q674L1595; used in Y594R1185. Y594R1672aWirin

differences

(

old=new

)

W2=W, Z=no connection,

K=X, W=G, W1=H, X=B.

R1210 101 Obsolete. Roca lo

o; °C scaleplate; used with

Q674L1017. Y594R1243aWirin

differences

(

old=new

)

W=W2, X=L, B=X.

R1228 120 Obsolete. York lo

o; part no. 2TH11702524A; °C

scaleplate; used with Q674L1272 and C815A1005;

used in Y594R1144.

Y594R1672a

R1236 115 Obsolete. Williamson lo

o; includes Allen wrench and

screws to lock cover; used with Q674L1348. T874R1152

R1244 115 Obsolete. Westin

house lo

o; used with Q674L1314

and W89. T874R1152/

Y594R1243a

R1251 120 Obsolete. York lo

o; part no. 2TH11702324A; H2

anticipator is fixed; used with Q674L1272 and

C815A1039.

Y594R1672a

R1269 122 Obsolete. Fedders multi lo

o; part no.

THTX-120-HEHB 88-58-00540-001; used with

Q674L1066; used in Y594R1037.

Y594R1615aWirin

differences

(

old=new

)

K=E, C=X, W1=B, Z=L.

R1285 123 Obsolete. Hone

well lo

o; Rheem part no. 41-20796-

15; used with Q674L1157. Y594R1243a

R1301 113 Obsolete. Comfortmaker lo

o; part no. 1505-714; used

with Q674L1181; used in Y594R1417. Y594R1243aWirin

differences

(

old=new

)

X1=X.

Table 8. T874 Cross Reference.

Model

Number Fig.

No. Description Trade Model

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

67 60-2485—8

R1319 191 Obsolete. Carrier part no. 42QH400083; used with

Q674B1281 on two speed fan applications. See OEM for

replacement.

R1327 120 Obsolete. Bor

-Warner multi-lo

o; part no.

6TH11702224A; used with Q674L1272; used in

Y594R1193.

Y594R1672a

R1335 106 Obsolete. BDP multi-lo

o; part no. HH641501; H2

anticipator factor

set 1.2A; used with Q674L1405; used

in Y594R1201.

Y594R1243a

R1343 133 Obsolete. Fedders multi-lo

o; part no.

THTX-120-HEHC 88-58-0056-001; used with

Q674L1413; used in Y594R1219.

Y594R1425aWirin

differences

(

old=new

)

K=E, C=X1, Z=L; remove

Y1-W1

umper.

R1350 113 Obsolete. Hone

well lo

o; used with Q674L1181. Y594R1243aWirin

differences

(

old=new

)

X1=X.

R1368 125 Obsolete. Coleman lo

o; part no. 3600-368; used with

Q674L1421; used in Y594R1235. Y594R1797a

R1376 115 Hone

well lo

o; °C scaleplate; used with Q674L1207. T874R1152

R1384 131,

135 Obsolete. Carrier Heat Pump S

stem Control lo

o; part

no. HH07AQ170; used with Q674L

(

HH93AZ187

)

Q674L

(

HH93AZ197

)

, or Q674L

(

HH93AZ198

)

Y594G1243aWirin

differences

(

old=new

)

C=X.

R1392 128 Obsolete. Williamson lo

o; used with Q674L1447; used

in Y594R1250. Y594R1425aWirin

differences

(

old=new

)

A=L.

R1400 113 Obsolete. LSI part no. 104710001; used with

Q674L1181, L1462. See subbase description for

replacement information.

R1426 136 Obsolete. Trane Weathertron Heat Pump lo

o; part no.

BAYSTAT339

(

WY28X0112

)

; °F/°C scaleplate; used

with Q674L1496; used in Y594R1284.

Y594R1763a

R1434 134 Ruud lo

o; part no. 41-20796-32; used with Q674L1504;

used in Y594R1649. Y594R1300a

R1442 134 Rheem lo

o; part no. 41-20796-28; used with

Q674L1504; used in Y594R1631. Y594R1300a

R1459 134 Obsolete. Hone

well lo

o; Rheem part no. 41-20796-

25; used with Q674L1504. Y594R1300a

R1467 108 Hone

well lo

o; used with Q674L1512; used in

Y594R1292. Y594R1292a

R1475 123 Hone

well lo

o; scale ran

e 42°F to 88°F; used with

Q674L1520; used in Y594R1300. Y594R1300a

R1483 130 Obsolete. Comfortmaker lo

o; °F/°C scaleplate; used

with Q674L1538 and C815A1005; used in Y594R1318. Y594R1763aWirin

differences

(

old=new

)

W1=W, E=X2, X=F, C=B.

R1491 137 Obsolete. Hone

well lo

o; TRADELINE model; used

with Q674L1553; used in Y594R1326. Y594R1615a

R1509 47 Obsolete. Slant/Fin lo

o; used with Q674B1042; used in

Y594R1334. Y594R1243aWirin

differences

(

old=new

)

W1=W2.

R1517 130 Obsolete. Arcoaire lo

o; part no. 150671; used with

Q674L1538 and C815A1005; used in Y594R1342. Y594R1763aWirin

differences

(

old=new

)

W1=W, E=X2, X=F, C=B.

R1525 113 Obsolete. Arcoaire lo

o; used with Q674L1181; used in

Y594R1359. Y594R1243aWirin

differences

(

old=new

)

X1=X.

R1541 67 Obsolete. Goettl lo

o; part no. 372071; used with

Q674B1349. Y594R1300a

R1558 134 Obsolete. Universal Parts lo

o; part no. 41-20796-45;

used with Q674L1504; used in Y594R1623. Y594R1300a

R1566 130 Obsolete. Hone

well lo

o; used with Q674L1538 and

C815A1005; used in Y594R1375. Y594R1763aWirin

differences

(

old=new

)

W1=W, E=X2, X=F, C=B.

Table 8. T874 Cross Reference.

Model

Number Fig.

No. Description Trade Model

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—868

R1574 132 Obsolete. Comfortmaker lo

o; part no. 1505739; used

with Q674L1538; used in Y594R1383. Y594R1243aWirin

differences

(

old=new

)

C=X, X=L, W=W2.

R1582 132 Obsolete. Arcoaire lo

o; part no. 150739; used with

Q674L1538; used in Y594R1391. Y594R1243aWirin

differences

(

old=new

)

C=X, X=L, W=W2.

R1590 115 Obsolete. Refac lo

o; used with Q674L1207. T874R1152/

Y594R1243a

Replacement has °F

scaleplate.

R1608 119 Obsolete. Hone

well lo

o; Intertherm heat pump; used

with Q674L1264; used in Y594R1409. Y594R1763aWirin

differences

(

old=new

)

W2=W, X=B, Z=F, K=X2,

W1=O.

R1616 168 Hone

well lo

o; SUPER TRADELINE® model; used

with Q674L1587; used in Y594R1425. Y594R1425a

R1624 200 Obsolete. Hone

well lo

o; used with Q674L1595; used

in Y594R1433. Y594R1243aWirin

differences

(

old=new

)

X=B, Z=F, W2=W, K=X2,

W1=O.

R1632 134 Obsolete. Hone

well lo

o; used with Q674L1603. Y594R1243a

R1640 115 Obsolete. Hitecsa lo

o; °C scaleplate; H2 anticipator

factor

set at 1.2A; used with Q674L1207. Y594R1243aReplacement has °F

scaleplate.

R1657 136 Obsolete. American Standard lo

o; part no.

ASYSTAT651; re

uires outdoor reset; used with

Q674L1611; used in Y594R1441.

Y594R1763a

R1673 108 Heil lo

o; part no. 1060321, HAXB004TW01; used with

Q674L1132; used in Y594R1466. Y594R1292a

R1699 119 Obsolete. Miller lo

o; used with Q674L1264; used in

Y594R1482. Y594R1763aWirin

differences

(

old=new

)

W2=W, X=B, Z=F, K=X2,

W1=O.

R1707 209 Trol-A-Temp b

Hone

well lo

o; Premier White® color;

used with Q674L1678; used in Y594R1490. None See Trol-A-Temp for

replacement.

R1715 209 Trol-A-Temp b

Hone

well lo

o; used with Q674L1186;

used in Y594R1508. None See Trol-A-Temp for

replacement.

R1723 218 Obsolete. No lo

o; Sn

der General part no. 654958B07;

°F/°C scaleplate; used with Q674L1702 and

C815A1005; used in Y594R1516.

Y594R1672aWirin

differences

(

old=new

)

W1=W, X=X2, C=B.

R1731 108 Obsolete. Inter-Cit

Products lo

o; part no.

HQ11477909HW; used with Q674L1132; used in

Y594R1524.

Y594R1292a

R1749 108 Tempstar lo

o; part no. 1060322, TAXB004TW01; used

with Q674L1132; used in Y594R1532. Y594R1292a

R1814 108 Obsolete. Hone

well lo

o; Keeprite part no. THPC; °C

scaleplate; used with Q674L1132; used in Y594R1607. Y594R1292aReplacement has °F

scaleplate.

R1822 230 Hone

well lo

o; TRADELINE model; used with

Q674L1710; used in Y594R1615. Y594R1615a

R1830 134 Obsolete. Addison lo

o; WeatherKin

part no. 41-

20796-61; used with Q674L1504; used in Y594R1656. Y594R1300a

R1855 228 Obsolete. Lennox lo

o; Premier White® color; °C

scaleplate; outdoor reset re

uired

(

use C815A1005

)

;

used with Q674L1728; used in Y594R1714.

Y594R1763aWirin

differences

(

old=new

)

Y1=Y, L=F, W1=W, E=X2,

C=B; replacement has °F

scaleplate.

R1871 120 Hone

well lo

o; desi

ned to replace Y594R1011

(

York

part no. 2TH11702224

)

; used with Q674L1736; used in

Y594R1664.

Y594R1664a

Table 8. T874 Cross Reference.

Model

Number Fig.

No. Description Trade Model

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

69 60-2485—8

R1889 120 Hone

well lo

o; desi

ned to replace Y594R1151

(

York

part no. 2TH11702324

)

, Y594R1193

(

York part no.

6TH11702224

)

, and York part no. 2TH11704024; used

with Q674L1736 and C815A1054; used in Y594R1672.

Y594R1672a

R1897 230 Hone

well lo

o; Premier White® color; used with

Q674L1751; used in Y594R1680. Y594R1680a

R1905 120 Obsolete. Hone

well lo

o; Premier White® color;

desi

ned to replace Y594R1151

(

York part no.

2TH11702324

)

, Y594R1193

(

York part no.

6TH11702224

)

, and York part no. 2TH11704024; used

with Q674L1777 and C815A1054; used in Y594R1698.

Y594R1672aReplacement is bei

R1913 120 Obsolete. Hone

well lo

o; Premier White® color;

desi

ned to replace Y594R1011

(

York part no.

2TH11702224

)

; used with Q674L1777; used in

Y594R1706.

Y594R1664aReplacement is bei

R1921 115 Obsolete. Econar lo

o; used with Q674L1207; used in

Y594R1722. Y594R1243a

R1939 197 American Standard lo

(

Trane

)

; part no.

ASYSTAT651A; includes outdoor reset; used with

Q7674L1801; used in Y594R1748.

Y594R1763a

R1947 168 Obsolete. Inter-Cit

Products lo

o; part no.

HQ1149406HW; used with Q674L1819; used in

Y594R1755.

Y594R1425a

R1954 197 Hone

well lo

o; TRADELINE model; includes outdoor

reset; used with Q674L1827; used in Y594R1763. Y594R1763aDirect replacement for

Y594R1748

(

T874R1939/

Q674L1801

)

American

Standard lo

(

ASYSTAT

651A

)

and Y594R1136

(

T874R1053/Q674L1140

)

R1962 115 Obsolete. Consolidated Industries lo

o; part no.

9036100; Premier White® color; used with Q674L1843;

used in Y594R1771.

Y594R1680aIncludes CHECK LED.

R1970 120 York lo

o; Canada; Premier White® color; °C scaleplate;

used in Y594R1789; used with C815A1039. Y594R1672aReplacement has °F

scaleplate.

R1988 125 Hone

well lo

o; TRADELINE model; used with

Q674L1868; used in Y594R1797. Y594R1797 Direct replacement for

Y594R1235

(

T874R1368/

Q674L1421

)

Evcon/Coleman

part no. 3600-368.

R2002 245 Obsolete. Amana Air Conditionin

o; part no.

10574102; used in Y594R1805. Y594R1797 Wirin

differences

(

old=new

)

C/X=X.

R2010 245 Obsolete. Amana Air Conditionin

o; part no.

10574104. Y594R1797 Wirin

differences

(

old=new

)

C/X=X, W3=W2.

R2028 209 Obsolete. York lo

o; part no. 2TH11703424A; used with

Q674L1918 in Y594R1821. Y594R1797

R2036 134 Ruud lo

o; °C scaleplate; used with Q674L1504. See OEM for

replacement.

T874S 2-sta

e heat, 3-sta

e cool.

S1001 223 Obsolete. Carrier S

ner

2000 Heat Pump S

stem

Control lo

o; used with Q674F1501. T8611M2025

(

pro

rammable

)

or see OEM for

direct

replacement.

Includes ni

ht setback.

T874V 1-sta

e cool.

V1008 69 Obsolete. No lo

o; Carrier part no. HH07AT177; used

with Q674R1003. T874A1036

Table 8. T874 Cross Reference.

Model

Number Fig.

No. Description Trade Model

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—870

T874W 3-sta

e heat, 2-sta

e cool, manual chan

eover.

W1007 118 Obsolete. Hone

well lo

o; Westin

house special; used

with Q674L1256. T8611M2025

(

pro

rammable

)

Includes ni

ht setback.

W1015 54 Hone

well lo

o; used with Q674B1216 and C815A1005;

used in Y594W1014. T874W1015

W1023 233 Obsolete. Lennox Advanced Heat Pump S

stem lo

used with Q674L1280 and W89. T874W1015

W1031 140 Obsolete. No lo

o; Rheem part no. 41-20797-20; used

with Q674L1546 and C815A1005; used in Y594W1022. T8611M2025

(

pro

rammable

)

Includes ni

ht setback.

W1049 100 Obsolete. McQua

o; part no. 61202501; 12°F

intersta

e differential between H2 and H3 for ni

setback; used with Q674C1363.

T8611M2025

(

pro

rammable

)

Includes ni

ht setback.

W1056 220 Obsolete. McQua

/Sn

der General lo

o; part no.

1202501; 12°F differential between H2 and H3 for ni

setback; used with Q674C1363

(

61202502

)

See OEM for

replacement.

W1064 220 Obsolete. AAF/Sn

der General lo

o; part no.

066804408; 12°F differential between H2 and H3 for

ht setback; used with Q674C1363

(

66804408

)

See OEM for

replacement.

W1072 140 Obsolete. Hone

well lo

(

Inter-Cit

Products

)

; used in

Y594W1030. T8611M2025

(

pro

rammable

)

Includes ni

ht setback.

W1080 220 McQua

o; part no. 073318901; Premier White®

color; 12°F differential between H2 and H3 for ni

setback.

None

W1106 247 Obsolete. Addison lo

o; part no. 843-277; °F/°C

scaleplate; used with Q674L1934 in Y594W1055. T8611M2025

T874Y Heat pump model; 2-sta

e heat, 2-sta

e cool, heat or

cool auto chan

eover.

Y1005 210 Obsolete. Mammoth Water Source Heat Pump lo

used with Q674E1353; used in Y594Y1004. See OEM for

replacement.

Y1013 248 Obsolete. WaterFurnace lo

o; part no. TA21H03;

Premier White® color; °F/°C scaleplate; used with

Q674F1675

(

32003081

)

See OEM for

replacement.

Table 8. T874 Cross Reference.

Model

Number Fig.

No. Description Trade Model

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

71 60-2485—8

Table 9. Q674 Subbase Cross Reference.

Model

Number Fig.

No. Description Q674 Trade

Replacement Remarks

Q674A S

stem: HEAT-AUTO-COOL; Fan: AUTO-ON

A1001 71 Standard OEM. Q674A1019

A1019 71 TRADELINE® model; used with T874A-D. Q674A1019

A1035 71 Obsolete. Trane part no. BAS-0435; used with T874A-D. Q674A1019

A1043 71 Hone

well lo

o; TRADELINE model; Q674A1019

A1050 71 Obsolete. Standard OEM. Q674A1043

Q674B S

stem: HEAT-OFF-COOL; Fan: AUTO-ON

B1000 45 Standard OEM; used with T874C1570, C1695, C1703,

D1843; used in Y594C1363. Q674B1034

B1018 44 Standard OEM; used with T874B1035, D1082; used in

Y594B1026, D1016. Q674B1018

B1026 45 Obsolete. S

stem: HEAT-OFF-RESET-COOL. Q674B1034

B1034 45 TRADELINE Q674B1034

B1042 47 Obsolete. Used with T874R1004, R1509; used in

Y594R1029, R1334. Y594R1243aWirin

differences

(

old=new

)

W1=W2.

B1059 45 Obsolete. Factor

installed RC-RH

umper; used with

T874C1059; used in Y594C1256. Q674B1034 Field wire RC-RH.

B1075 46 Auto fan in heatin

and coolin

mode; used with

T874B1035, C1000, D1082; used in Y594D1040. Q674B1075

B1083 51 Obsolete. Carrier part no. HH93AZ178; factor

installed RC-RH

umper. Q674B1075aOne s

stem transformer onl

B1091 45 Obsolete. Carrier part no. HH93AZ184; factor

installed RC-RH

umper. Q674B1034

B1109 47 Obsolete. Addison heat pump; used with T874R1012. Y594R1243aWirin

differences

(

old=new

)

W1=W2.

B1117 44 Obsolete. Carrier part no. HH93AZ180; factor

installed RC-RH

umper. Q674B1018a

B1125 53 Obsolete. York part no. 2TB04700324A; used with

T874D1041. Q674B1075aJumper RC-RH; replacement

has no LOCKOUT LED.

B1133 48 Obsolete. Includes FILTER LED; used with

T874D1082; used in Y594D1156. Q674B1018

B1141 51 Trane part no. BAY28X185; automatic fan operation in

heat and cool mode. Q674B1075 Set T874 H1 anticipator for

combined load of heat rela

and fan rela

B1158 50 Obsolete. Used with T874G1071. T874C1018/

Q674B1018a

W1-Y1 and RH-RC

umpers

uired.

B1166 249 Carrier part no. HH93AZ179; factor

installed RC-RH

umper; LOCKOUT LED; used with T874C1075

(

HH07AT170

)

Y594C1421 or

Q674B1075a

Replacement onl

uires

one transformer and has no

LOCKOUT LED.

B1190 52 Obsolete. Wards special; factor

installed RH-RC and

F-W3

umpers; used with T874C1372. Gas Furnace:

Q674B1034

Electric Furnace:

Q674B1075

B1208 187 Obsolete. Used with T874C1422. None

B1216 54 Used with T874W1015 and C815A1005; used in

Y594W1014. Q674B1216

B1224 49 Obsolete. Lennox part no. 25F7301; four LEDs; used

with T874C1430. Q674B1034 Replacement has no LEDs.

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—872

B1240 234 Obsolete. Northrup heat pump; AUX HEAT LED; used

with T874G1139. Y594G1252aWirin

differences

(

old=new

)

Y1=Y2, W1=W2; EM HT

stem switch position is not

operational.

B1257 56 Obsolete. LSI-Mammoth; RESET LED; automatic fan

operation in heat and cool modes; used with

T874C1471; used in Y594C1314.

Q674B1075 Replacement has no LED.

B1273 57 Obsolete. McQua

part no. 860-442727B-00; S

stem:

OVERRIDE-HEAT-OFF-COOL; used with T874P1006. T874A1036/

Q674B1075a

Wirin

differences

(

old=new

)

Y=Y1, L=R, W=O;

umper Y1-

W1; no ni

ht setback.

T8600D2028

(

pro

rammable

)

Wirin

differences

(

old=new

)

L=R, W=O; W-Y

umper

uired; ni

ht setback.

B1281 191 Obsolete. Carrier no. 42QH400103; S

stem: HEAT-

OFF-COOL; Fan: LOW-HI-CONT; international

mbols on switches; used with T874R1319.

See OEM for

replacement.

B1299 46 Obsolete. Heil Quaker part no. HQ521714HW. Q674B1075

B1307 62 Obsolete. Includes two LEDs; used with T874F1122. T874F1015/

Q674D1040a

Replacement has no LEDs.

B1315 68 Obsolete. Friedrich part no. AQ5215; OVERRIDE and

SERVICE LEDs; used with T874P1022, P1030. T8600D2028

(

pro

rammable

)

Wirin

differences

(

old=new

)

L=R, W=O; W-Y

umper

uired; set dual fuel switch

to electric heat; ni

ht setback.

B1331 65 Obsolete. Includes two LEDs; used with T874A1002. Q674B1034 Replacement has no LEDs.

B1349 67 Obsolete. Goettl part no. 372072; used with

T874R1541. Y594R1300a

B1356 138 Obsolete. Carrier part no. HH93AZ192; used with

T874L1018

(

HH07AT178

)

.See OEM for

replacement.

B1372 44 Obsolete. Trane part no. BAS-0427; used with T874A-D. Q674B1018

B1380 46 Obsolete. Trane part no. BAS-0426; used with T874A-D. Q674B1075

B1398 48 Obsolete. Trane part no. BAS-0431; FILTER LED;

used with T874A-D. Q674B1034 Replacement has no LEDs.

B1406 172 Obsolete. Carrier part no. HH93AZ200; FAULT and

CHECK FILTER LEDs; used with T874H1070

(

HH07AT166

)

, T874H1088

(

HH07AT167

)

T874H1153

(

HH07AT167

)

; used in Y594H1046.

T874A1150/

Q674B1075a

Wirin

differences

(

old=new

)

Y=Y1;

umper W1-Y1;

replacement has no LEDs.

B1414 51 American Standard

(

Trane

)

part no. ASYSTAT1617. Q674B1075

B1448 215 Obsolete. Carrier part no. HH93A2202; Fan: Lo-Med-

h-On; used with T874L1059. See OEM for

replacement.

B1455 214 Obsolete. Carrier part no. HH93AZ208; Fan: Lo-Med-

h-On; used with T874A1424

(

HH07AT194

)

.See OEM for

replacement.

B1463 45 Trol-A-Temp; used with T874D1801. None See Trol-A-Temp.

B1471 45 Trol-A-Temp; used with T874D1827. None See Trol-A-Temp.

B1513 53 Obsolete. TRADELINE; exact replacement for

Q674B1125

(

York part no. 2TB04700324

)

.Q674B1075 Jumper RC-RH; replacement

has no LOCKOUT LED.

B1521 53 Obsolete. Carrier Canada part no. HH93AZ179-W;

color; includes LOCKOUT LED and removable

umpers between RC and RH terminals.

Q674B1075 Jumper RC-RH; replacement

has no LOCKOUT LED; bei

color.

B1539 45 Obsolete. Carrier part no. HH93AZ139; used with

T874D2049; used in Y594D1370. Q674B1034

B1547 237 Obsolete. TRADELINE;

color; used with

T874C1810; used in Y594C1389. Y594C1389

Table 9. Q674 Subbase Cross Reference.

Model

Number Fig.

No. Description Q674 Trade

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

73 60-2485—8

B1554 82 Obsolete. TRADELINE; includes LOCKOUT LED and

removable

umpers between RC and RH terminals;

used with T874C1877; used in Y594C1421.

Y594D1347 Jumper RH-RC; s

stem

switch: Off-HEAT-AUTO-

COOL.

B1562 45 Obsolete. Amana lo

o; part no. P1217701F;

removable

umpers between RC and RH terminals. Q674B1034

B1570 45 Obsolete. Armstron

o; part no. 03299A18. Q674B1034 Replacement is bei

B1588 45 Obsolete. Standard OEM. Q674B1034 Replacement is bei

Q674C S

stem: OFF-AUTO; Fan: AUTO-ON

C1009 72 Standard OEM; used with T874D1082; used in

Y594D1024. Q674C1058

C1017 Obsolete. Includes factor

-installed RC-RH

umper;

used with T874A,F,Q. Q674C1058

C1033 72 Trane part no. BAY28X187. Q674C1058

C1041 74 Obsolete. Command Aire heat pump; used with

T874H1005, H1054. Y594H1012aWirin

differences

(

old=new

)

Y1=O, Y2=Y; W-Y

umper

uired.

C1058 72 TRADELINE Q674C1058

C1066 73 Obsolete. Command Aire heat pump; used with

T874G1352. Y594H1012aWirin

differences

(

old=new

)

Y1=O, Y2=Y, L=R, R=none; R-

umper re

uired; no ni

setback.

T8600D2028

(

pro

rammable

)

Wirin

differences

(

old=new

)

Y1=O, Y2=Y, L=R; W-Y

umper re

uired; ni

setback.

C1074 81 Obsolete. Used with T874C1018. Q674C1058 Jumper W2-Y1 and RH-RC.

C1090 77 Obsolete. LSI-Mammoth heat pump; used with

T874K1001. Y594R1419aWirin

differences

(

old=new

)

RH-RC=R, W1=B, W3=W2,

W2=W1; remove Y1-W1

umper.

C1108 143 Obsolete. Northrup special; AUX HEAT LED; used with

T874G1139. Y594R1243aWirin

differences

(

old=new

)

Y1=Y, W1=W2, C=X.

C1116 76 Obsolete. McQua

part no. 02005959; two LEDs; used

with T874D1116. Q674C1058 Replacement has no LEDs.

C1124 79 Obsolete. LSI-Mammoth heat pump; RESET LED;

used with T874G-H; used in Y594G-H. Y594G1294

T8600D2028

C1132 75 Obsolete. McQua

part no. 03005049; sprin

return

momentar

stem switch position; used with

T874A1283.

See OEM for

replacement.

C1140 78 Obsolete. McQua

no. 860-442728B-00; S

stem:

OVERRIDE-AUTO-OFF; used with T874P1006. T8600D2028

(

pro

rammable

)

Wirin

differences

(

old=new

)

L=R, W=O; W-Y

umper

uired; ni

ht setback.

C1157 72 Obsolete. York part no. 2TB04700124A. Q674C1058

C1165 192 Obsolete. McQua

part no. 03005050; sprin

return

momentar

stem switch position. See OEM for

replacement.

C1173 96 Obsolete. American Air Filter part no. 4ELN-8787;

used with T874C1133. Q674C1058 Replacement has no LEDs.

C1181 76 Obsolete. California heat pump; used with T874C1000. Q674C1058

C1199 163 Obsolete. American Air Filter part no. 4ELN-8788; two

LEDs; sprin

return momentar

stem switch position;

used with T874G1485, G1535.

T8600D2028 No momentar

reset switch.

Table 9. Q674 Subbase Cross Reference.

Model

Number Fig.

No. Description Q674 Trade

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—874

C1207 78 Obsolete. Friedrich; S

stem: OVERRIDE-AUTO-OFF;

used with T874P1014. T8600D2028

(

pro

rammable

)

Wirin

differences

(

old=new

)

L=R, W=O; W-Y

umper

uired; ni

ht setback.

C1215 97 Obsolete. Friedrich part no. AQ5315; S

stem:

OVERRIDE-AUTO-OFF; OVERRIDE and SERVICE

LEDs; used with T874P1022, P1030.

T8600D2028

(

pro

rammable

)

Wirin

differences

(

old=new

)

L=R, W=O; W-Y

umper

uired; ni

ht setback.

C1223 73 Obsolete. Friedrich part no. AQ5323; used on s

stems

uirin

ht setback contacts; used with

T874G1584.

Y594H1012aWirin

differences

(

old=new

)

Y1=O, Y2=Y, L=R, R=none; R-

umper re

uired; no ni

setback.

T8600D2028

(

pro

rammable

)

Wirin

differences

(

old=new

)

L=R, W=O; W-Y

umper

uired; ni

ht setback.

C1249 164 Includes MALFUNCTION LED; used with T874H1062;

used in Y594H1012. Y594H1012a

C1256 73 Obsolete. Used with T874G1618. Y594H1012aWirin

differences

(

old=new

)

Y1=O, Y2=Y, L=R, R=none; R-

umper re

uired; no ni

setback.

T8600D2028

(

pro

rammable

)

Wirin

differences

(

old=new

)

L=R, W=O; W-Y

umper

uired; ni

ht setback.

C1264 165 Obsolete. Carrier part no. HH93AZ193; used with

T874L1018

(

HH07AT178

)

.See OEM for

replacement.

C1280 181,

203 Obsolete. McQua

heat pump; part no. 60687401;

COMP FAULT LED; used with T874K1019, L1034. T8600D2028 See thermostat description for

replacement information.

C1298 76,

225 Obsolete. McQua

part no. 60684801; SERVICE LED;

used with T874A1523, A1549, D1918. See OEM for

replacement.

C1306 75 Obsolete. McQua

part no. 60685001; SERVICE LED;

sprin

return momentar

stem switch position; used

with T874A1325.

See OEM for

replacement.

C1314 72 Obsolete. Trane part no. BAS-0429; used with T874A-F. Q674C1058

C1322 173 Obsolete. Carrier part no. HH93AZ199; FAULT and CK

FILTER LEDs; used with T874H1070

(

HH07AT166

)

T874H1088

(

HH07AT167

)

or T874H1153

(

HH07AT167

)

; used in Y594H1053.

Y594H1012aWirin

differences

(

old=new

)

2=X.

C1330 177 Obsolete. LSI-Mammoth part no. 71115201; RESET

LED; used on s

stems with ni

ht setback contacts;

used with T874G1659, H1096; used in Y594G1427,

H1020.

Y594H1012aWirin

differences

(

old=new

)

R1=R; R2=L.

C1355 74 Friedrich part no. AQ355; SERVICE LED; used with

T874H1112. Y594H1012aWirin

differences

(

old=new

)

Y1=O, Y2=Y; L-R

umper

uired.

C1363 99 Obsolete. McQua

part no. 61202601; SERVICE LED;

auto fan in heat and cool mode; used with T874C. T874C1125/

Q674B1075a

Replacement has HEAT-OFF-

COOL.

219 Obsolete. Used with T874C. See OEM for

replacement.

220 Obsolete. Used with T874W. See OEM for

replacement.

100 Obsolete. Used with T874W. T8611M2025

(

pro

rammable

)

Includes ni

ht setback.

C1371 72 American Standard part no. ASYSTAT616. Q674C1058

Table 9. Q674 Subbase Cross Reference.

Model

Number Fig.

No. Description Q674 Trade

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

75 60-2485—8

C1389 205,

176 Obsolete. Command Aire part no. P1099-0021; two

LEDs; used with T874G-H. None See thermostat description for

replacement information.

C1397 205,

171 Obsolete. Command Aire part no. P1099-0023; used

with T874G-H. None See thermostat description for

replacement information.

C1413 213 Obsolete. Carrier part no. HH93AZ204; Fan: Lo-Med-

h-On; used with T874L1059. See OEM for

replacement.

C1439 217 Obsolete. Bard part no. 8404-016; used with

T874N1024. See OEM for

replacement.

C1454 163 Obsolete. Climate Master part no. AQ5354; two LEDs;

sprin

return momentar

stem switch position. Y594G1393aNo momentar

reset switch.

C1462 25 Climate Master Special. Q674C1058 Replacement has no LEDs.

C1470 221 Obsolete. Climate Master part no. RQ5370; used with

T874H1138. Y594H1012aWirin

differences

(

old=new

)

Y1=O, Y2=Y; replacement has

MALFUNCTION LED onl

C1496 74 Obsolete. Carrier part no. HH93AZ213; includes

SERVICE LED; used with T874H1161; used in

Y594H1038.

Y594H1012aWirin

differences

(

old=new

)

Y1=O, Y2=Y; L-R

umper

uired.

C1504 83 Obsolete. Carrier part no. HH93AZ214; used in Y594. Y594H1012aWirin

differences

(

old=new

)

Y1=O, Y2=Y, L=R, R=none; R-

umper re

uired; no ni

setback.

T8600D2028

(

pro

rammable

)

Wirin

differences

(

old=new

)

Y1=O, Y2=Y, L=R; W-Y

umper re

uired; ni

setback.

C1512 97 Obsolete. Carrier part no. HH93AZ216; S

stem:

Override-Auto-Off; includes two LEDs; used in Y594. T8600D2028

(

pro

rammable

)

Wirin

differences

(

old=new

)

L=R, W=O; W-Y

umper

uired; ni

ht setback.

C1520 72 Obsolete. Carrier part no. HH93AZ210; used with

T874D2049; used in Y594D1388. Q674C1058

C1538 163 Climate Master part no. AQ5354; S

stem: Off-Auto-

Override; includes two LEDs and momentar

sprin

position.

Y594G1393 No momentar

reset switch.

C1546 76,

225 Obsolete. McQua

part no. 060684802;

color;

includes one LED. Q674C1058 Replacement has no LEDs;

bei

e color

C1553 181,

203 Obsolete. McQua

o; part no. 073319901; includes

one LED. Q674C1058 Replacement is bei

C1561 76 McQua

o; part no. 073319701; includes one LED. See OEM for

replacement.

C1579 99,

100 McQua

o; part no. 073320001; includes one LED. See OEM for

replacement.

C1595 72 Obsolete. Standard OEM. Q674C1058

Q674D S

stem: None; Fan: None

D1008 55, 66 Obsolete. Used with T874D1082, F1056; used in

Y594D1057. Q674D1040

D1016 55 Obsolete. Carrier part no. HH93AZ170; RC-RH

umper. Q674D1040 RC-RH

umper re

uired.

D1032 58 Obsolete. Bor

-Warner; used with T874G. T874D1165/

Q674D1040a

Wirin

differences

(

old=new

)

Y=Y2, O=Y1, W=W2;

umper

W1-Y2 re

uired.

D1040 55 TRADELINE Q674D1040

D1057 55, 66 Obsolete. York part no. 2TB04700424A. Q674D1040

Table 9. Q674 Subbase Cross Reference.

Model

Number Fig.

No. Description Q674 Trade

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—876

D1065 63 Obsolete. Includes two LEDs; used with T874F1122. T874F1015/

Q674D1040a

Replacement has no LEDs.

D1099 55, 66 Obsolete. Trane part no. BAS-0430; used with T874A-F. Q674D1040

D1107 55, 66 Obsolete. Sn

der General part nos. 654958801/

1520503/ 4ELN30070. Q674F1040.

D1115 208 Trol-A-Temp; used with T874D1801. None See Trol-A-Temp.

D1123 208 Trol-A-Temp;

color; used with T874D1827. None See Trol-A-Temp.

D1156 55 Obsolete. Gra

color; includes removable

umper

between RC and RH terminals. Q674D1040 Replacement is bei

e color.

D1164 66 Obsolete. Carrier part no. HH93AZ211; used in

Y594D1440. Q674D1040

D1172 208 Obsolete. Amana lo

o; part no. P121501F; removable

umpers between RC and RH terminals. Q674D1040

D1180 55 Obsolete. York lo

o; part no. 2TH04703224A. Q674D1040

D1198 55, 66 Obsolete. Standard OEM. T874D1165/

Q674D1040 Replacement is bei

e color.

Q674E S

stem: OFF-HEAT-AUTO-COOL; Fan: AUTO-ON

E1007 82 Used with T874D1504; used in Y594D1180. Q674E1049

E1015 84 Obsolete. Lennox heat pump; used with T874G1006,

G1154. Y594G1252aWirin

differences

(

old=new

)

R=O, M=Y, F=G, V=R, Y=W2;

E-W2

umper re

uired.

E1049 193 TRADELINE; used with T874D2031 and TG504A1025;

used in Y594D1354. Q674E1049

E1056 82 Obsolete. Amana part no. D68535-7; used with

T874C1059, C1331; used in Y594C1009. Q674E1049 RC-RH

umper re

uired.

E1064 83 Obsolete. RC-RH

umpered internall

; EM HEAT LED. Q674E1049

E1072 82 Carrier part no. HH93AZ176; RC-RH

umpered

internall

.Q674E1049 RC-RH

umper re

uired.

E1080 82 Trane part no. BAY28X184. Q674E1049

E1098 85 Obsolete. Used with T874A-D. Q674E1049 RC-RH

umper re

uired.

E1106 185 Obsolete. ITT Nesbitt. See OEM for

replacement.

E1114 87 Carrier part no. HH93AZ177; RC-RH

umper;

LOCKOUT LED to indicate compressor lockout; used

with HH07AT series thermostats.

Q674E1049 RC-RH

umper re

uired;

replacement has no LED.

E1122 83 Obsolete. S

uare D part no. 63600-002-10; CHECK

LED. Q674E1049 Replacement has no LED.

E1148 86 Obsolete. Lennox heat pump; used with T874G1014,

G1022. Y594G1252aWirin

differences

(

old=new

)

R=O, M=Y, F=G, Y=W2,

V-VR=R; must use sin

transformer.

E1155 88 Obsolete. Lennox part no. 91C7501; HIGH and LOW

LEDs; used with T874B1076, D1017. Q674E1049 Replacement has no LEDs.

E1197 89 Obsolete. McQua

part no. 02005961; two LEDs; used

with T874D1116. Q674E1049 Wirin

differences

(

old=new

)

D=O; replacement has no

LEDs.

E1205 80 Obsolete. Fedders special; SERVICE LED; used with

T874D1462. Q674E1049 Replacement has no LEDs.

E1213 82 York part no. 2TB04700224A. Q674E1403

E1221 82 Heil Quaker part no. HQ712003HW. Q674E1049

Table 9. Q674 Subbase Cross Reference.

Model

Number Fig.

No. Description Q674 Trade

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

77 60-2485—8

E1262 82 Lennox part no. 13F1701. Q674E1049

E1270 198 Obsolete. Carrier part no. HH93AZ189; used with

T874L1000

(

HH07AT176

)

.Y594G1419aE-W2

umper re

uired.

E1304 82 Obsolete. BDP part no. P272-1887; used with

T874L1026. Y594G1419aE-W2

umper re

uired.

E1312 224 Obsolete. McQua

part no. 60684901; one LED; used

with T874A1523, A1549, D1686, D1918. Q674E1049 Replacement has no LEDs.

E1320 82 Obsolete. Trane part no. BAS-0434. Q674E1049

E1338 88 Obsolete. Goodman part no. CHTS36-60; HIGH and

LOW LEDs; used with T874B1100; used in

Y594B1042.

Q674E1049 Replacement has no LEDs.

E1346 82 Obsolete. Sn

der General part nos. 1505753/1506753/

654958B02; used with T874D1769; used in

Y594D1297.

Q674E1049

E1353 210 Obsolete. Mammoth; used with T874Y1005; used in

Y594Y1004. T8611M2025

E1379 212 Trol-A-Temp b

Hone

well; used with T874A1465. None See Trol-A-Temp.

E1395 222 Obsolete. Carrier part no. HH93AZ209; used with

T874B1134

(

HH07AT199

)

.T874B1019/

Q674E1049a

Wirin

differences

(

old=new

)

W1 =W; RC-RH

umper

uired; replacement has no

LEDs.

E1403 82 TRADELINE; desi

ned to replace York 2TH04701024;

used with T874D1942; used in Y594D1347. Y594D1347a

E1411 82 Obsolete. Carrier Canada part no. HH93AZ176-W;

color; removable

umper between RC and RH

terminals.

Q674E1049 RC-RH

umper re

uired.

Replacement is bei

e color.

E1429 87 Carrier Canada part no. HH93AZ177-W;

color;

includes LOCKOUT LED; removable

umper between

RC and RH terminals.

Q674E1049 RC-RH

umper re

uired.

Replacement has no LOCK-

OUT LED and is bei

e color.

E1445 82 Obsolete. Carrier part no. HH93AZ217-W;

color;

removable

umper between RC and RH terminals. Q674E1049 RC-RH

umper re

uired.

Replacement is bei

e color.

E1460 224 McQua

o; part no. 073319801; includes one LED.

E1478 82 Obsolete. Armstron

o; part no. 03299A19. Q674E1049 RC-R

umper re

uired.

Replacement is bei

e color.

E1486 82 Obsolete. Standard OEM. Q674E1049 RC-R

umper re

uired.

Replacement is bei

e color.

Q674F S

stem: EM.HT.-HEAT-AUTO-COOL-OFF;

Fan: AUTO-ON

F1006 141 Obsolete. Includes EM HEAT LED; used with

T874C1331. Q674F1022 Jumper E-X2.

F1022 142 Includes LED and field selectable inserts; used with

T874C1059; used in Y594C1017, C1330. Q674F1022

F1030 146 Carrier part no. HH93AZ174; SUPL HEAT LED; used

with T874D1074

(

HH07AT172

)

.Q674F1022 Wirin

differences

(

old=new

)

C=X1, X=X2.

F1048 149 Obsolete. Includes EM HEAT LED and auxiliar

power

terminal Z. Q674F1022 Replacement does not include

Z terminal and onl

uires

one transformer.

F1063 146 Obsolete. Carrier part no. HH93AZ181; SUPL HEAT

LED; used with T874D1074

(

HH07AT172

)

.Q674F1022 Wirin

differences

(

old=new

)

C=X1, X=X2.

F1071 142 Obsolete. S

uare D part no. 63600-002-11; CHECK

LED. Q674F1022

Table 9. Q674 Subbase Cross Reference.

Model

Number Fig.

No. Description Q674 Trade

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—878

F1089 152 Obsolete. Includes EM HEAT LED; X2-E and RC-RH

umpers. Q674F1022

F1097 142 Obsolete. Southwest special; W2-X2

umper. Q674F1022

F1105 145 Obsolete. Lennox heat pump; EM HEAT LED; used

with T874G1154. Y594G1252aWirin

differences

(

old=new

)

V=R, Y=W2, F=G, X2=X,

R=O, M=Y; L-E

umper

uired.

F1113 150 Obsolete. Lennox heat pump; part no. 24F6201; V-VR

umper; EM HEAT LED; chan

eover in coolin

; used

with T874G1014, G1022.

Y59461252aWirin

differences

(

old=new

)

R=O, M=Y, F=G, Y=WC,

V=VR=R; must use sin

transformer.

F1121 153 Obsolete. Westin

house heat pump; EM HEAT LED;

used with T874G1048. Y594G1252a

F1139 148 Obsolete. Tappan heat pump; EM HEAT LED; auto fan

in emer

enc

heat mode; used with T874G1147. Y594G1252aWirin

differences

(

old=new

)

C=X.

F1162 151 Obsolete. Crispaire heat pump; EM HEAT LED; used

with T874G. Y594G1393a

F1170 153 Obsolete. Heatwave

(

Southwest Mf

)

heat pump; EM

HT LED; used with T874G1105. Y594G1252a

F1188 153 Obsolete. Luxaire heat pump. Y594G1252a

F1196 178 Obsolete. Williamson; EM HEAT and SERVICE LEDs;

used with T874N1008; used in Y594N1007. Q674F1220

F1204 154 Obsolete. Special for Crispaire; EM HEAT and COMP

FAULT LEDs; used with T874G1089; used in

Y594G1153.

Y594G1393aWirin

differences

(

old=new

)

A=L.

F1212 155 Includes AUX HEAT and EM HEAT LEDs; used with

T874G1246, G1451, G1592, G1915; used in

Y594G1252.

Q674F1212 or

Y594G1252a

F1220 178 Used with T874N1016; used in Y594N. Q674F1220

F1238 155 Obsolete. Rheem part no. 41-20797-14; AUX HEAT

and EM HEAT LEDs; used with T874G1097, G1212,

G1220, G1238.

Y594G1252a

F1246 156 Obsolete. Westin

house heat pump; EM HEAT and

AUX HEAT LEDs; auto fan in emer

enc

heat mode;

chan

eover in coolin

mode.

Y594G1252a

F1253 157 Obsolete. Wesco/Addison heat pump; used with

T874G1261, G1279, G1287. Y594G1252aWirin

differences

(

old=new

)

Y1=O, C=X, W1=Y, X=L.

F1261 179 Includes two LEDs; used with T874N1024; used in

Y594N. Y594G1419aWirin

differences

(

old=new

)

L=X2, Y=Y1.

F1279 158 Obsolete. Westin

house heat pump; two LEDs; used

with T874G. Y594G1252aWirin

differences

(

old=new

)

L1=L.

F1295 147 Obsolete. Keeprite/Westin

house heat pump;

SERVICE, AUX HEAT and EM HEAT LEDs; used with

T874G1188.

Y594G1252aWirin

differences

(

old=new

)

S=L; replacement does not

include A or T terminals.

F1311 155 York heat pump; AUX HEAT and EM HEAT LEDs; used

with T874G1410. Y594G1252a

F1329 142 Obsolete. Heil Quaker part no. HQ712005HW; one

LED and field selectable inserts. Q674F1022

F1337 166 Obsolete. WeatherKin

heat pump; two LEDs and field

selectable inserts; used with T874D1009; used in

Y594D1222.

Q674F1022 Wirin

differences

(

old=new

)

R=RC-RH; replacement has

no LEDs.

Table 9. Q674 Subbase Cross Reference.

Model

Number Fig.

No. Description Q674 Trade

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

79 60-2485—8

F1345 194 Obsolete. Addison heat pump; EM HEAT and CHECK

LEDs; used with T874G; used in Y594G. Y594G1252aWirin

differences

(

old=new

)

Y1=O, C=X, W1=Y, X=L.

F1360 167 Obsolete. Rheem part no. 41-20797-17; AUX HEAT

and EM HEAT LEDs; used with T874G1493. Y594G1526a

F1378 195 Obsolete. Includes EM HEAT and AUX HEAT LEDs;

used with T874G1501. Y594G1252aWirin

differences

(

old=new

)

L1=L; chan

eover in coolin

onl

F1394 139 Obsolete. Nepco heat pump; HEAT PUMP and AUX

HEAT LEDs; S

stem: AUX HEAT-HEAT PUMP-2

STAGE HEAT-OFF-COOL; used with T874D1595.

T874D1165/

Q674B1018a

Replacement has HEAT-OFF-

COOL s

stem switchin

and

no LEDs.

F1402 169 Obsolete. Coleman heat pump; two LEDs; used with

T874G1576; used in Y594G1377. Y594G1633a

F1410 170 Used with T874G1246, G1915; used in Y594G1393. Y594G1393a

F1428 199 Obsolete. Used with T874G1600; used in Y594G1401. Y594G1419aWirin

differences

(

old=new

)

umper W1-Y1.

F1436 167 Includes AUX HEAT and EM HEAT LEDs; chan

eover

in heatin

mode; used with T874G1626; used in

Y594G1526.

None

F1444 227 Includes AUX HEAT, EM HEAT and CHECK LEDs;

used with T874G1642; used in Y594G1419. Y594G1419a

F1451 204 Obsolete. York part no. 2TB047700524A; one LED and

field selectable inserts. Q674F1012 Wirin

differences

(

old=new

)

X2=X; X1=B.

F1477 227 TRADELINE;

color; used with T874G1741,

G1824; used in Y594G1476, G1534. Y594G1476a

F1485 211 Trol-A-Temp b

Hone

well; chan

eover is provided b

Trol-A-Temp zone panel; used with T874G1758; used

in Y594G1492.

None See Trol-A-Temp.

F1501 223 Obsolete. Carrier two-speed compressor heat pump;

used with T874S1001. T8611M2025

(

pro

rammable

)

Includes ni

ht setback.

F1519 231 Obsolete. Nord

ne; used with T874G1832, G1840;

used in Y594G1542, G1559. Y594G1252aReplacement has auto

chan

eover in coolin

mode

onl

F1535 229 Obsolete. Lennox heat pump;

color; used with

T874G1857; used in Y594G1583. Y594G1161aWirin

differences

(

old=new

)

E=X2, C=B, L=F.

F1543 204 Obsolete. TRADELINE Q674F1022 Wirin

differences

(

old=new

)

X2=X, X1=B.

F1550 243 Obsolete. Amana part no. 10573901; includes two

LEDs; used with T874G1899; used in Y594G1591. Y594G1633

F1568 155 Obsolete. Gra

color; includes two LEDs; used with

onl

T874G1931. Y594G1476 Y1-W1

umper re

uired.

F1584 169 TRADELINE; includes two LEDs; used with

T874G1972; used in Y594G1633. Direct replacement

for Coleman/Evcon Y594G1377

(

T874G1576/

Q674D1402

)

; Coleman part no. 3600-373.

Y594G1633a

F1592 238 Heat Controller; Fan: AUTO-ON; S

stem: AUX HEAT-

HEAT PUMP- 2 STAGE HEAT-OFF-COOL; includes

two LEDs; used with T874C1844; used in Y594C1413.

Y594R1425 E-W2

umper re

uired; s

stem

switch: EM.HT.-HEAT-OFF-

COOL.

F1600 169 Obsolete. Amana part no. 10573903; includes two

LEDs; used with T874G1980; used in Y594G1641. Y594G1633 Wirin

differences

(

old=new

)

;

W3=W2.

F1634 139 Standard OEM; S

stem: AUX HEAT-HEAT PUMP-

2 STG HEAT-OFF-COOL; includes two LEDs; used

with T874D2155.

Y594G1716

Table 9. Q674 Subbase Cross Reference.

Model

Number Fig.

No. Description Q674 Trade

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—880

F1667 155 WaterFurnace lo

o; part no. TA21H03; S

stem: OFF-

AUTO-HEAT-EM HT; includes two LEDs; used with

T874G2046.

Y594G1716

F1675 248 Obsolete. WaterFurnace lo

o; part no. TA21H03;

includes four LEDs. See OEM for

replacement.

Q674G S

stem: OFF-AUTO; Fan: None

G1005 184 Obsolete. Used in Y594F1063. Q674G1070

G1013 186 Obsolete. Climate Control; used with T874D1298. See OEM for

replacement.

G1021 91 Obsolete. Includes O and B terminals; used with

T874A-F,Q or T874D1082; used in Y594D1032. Q674G1070

G1047 92 Obsolete. Used with T874C1018, C1125. T8611

G1054 188 Obsolete. Sin

er part no. 0200-5963; used with

T874D1298. See OEM for

replacement.

G1062 232 Obsolete. Sin

er; used with T874D1298. See OEM for

replacement.

G1070 91 TRADELINE Q674G1070

G1088 92 Obsolete. LSI-Mammoth part no. 71120201; used with

T874C. See OEM for

replacement.

G1096 90 Obsolete. Climate Control part no. 02005958; used

with T874D1439, D1447. See OEM for

replacement.

G1104 94 Obsolete. McQua

part no. 0200-5963; two LEDs;

used with T874D1116. See OEM for

replacement.

G1120 202,

226 Obsolete. McQua

part no. 60684701; two SERVICE

LEDs; no fan switchin

; used with T874D1694, G1926. See OEM for

replacement.

G1138 91 Obsolete. Trane part no. BAS-0433; used with T874A-F. Q674G1070

G1153 184 Obsolete. Carrier part no. HH93AZ212; used in

Y594D1396. Q674G1070

G1161 184 Gra

color. Q674G1070 Replacement is bei

e color.

G1179 202 Obsolete. McQua

o; part no. 073319601; includes

two LEDs. Q674G1161 Replacement has no LEDs.

Q674J S

stem: EM.HT.-AUTO-OFF; Fan: AUTO-ON

J1001 180 Obsolete. Sin

er heat pump part no. 02005964; EM

HEAT LED; chan

eover heat mode. See OEM for

replacement.

J1019 159 Obsolete. Westin

house heat pump; EM HT LED;

stem: EM.HT.-ON-OFF; used with T874G1048. Y594G1252aWirin

differences

(

old=new

)

W=W2.

J1027 160 Obsolete. York part no. 025-22291; EM HEAT LED;

auto fan in emer

enc

heat mode; chan

eover in cool

mode; used with T874G1170, G1196, G1428, G1345,

G1444; used in Y594G1013, G1138, G1229.

Y594G1567a

J1035 161 Carrier heat pump; part no. HH93AZ173; S

stem:

SUPL.HT.-ON-OFF; SUPL HEAT LED; used with

T874G1055

(

HH07AT171

)

Y594G1674a

J1043 162 TRADELINE heat pump model; desi

ned for use on

Trane heat pumps; AUX HT and EM HT LEDs; auto fan

in emer

enc

heat; chan

eover in coolin

mode; used

with T874G1204 and C815A1008; used in Y594G1161.

Q674J1043 or

Y594G1161a

Desi

ned for use on Trane

heat pumps.

J1050 183 Obsolete. Westin

house heat pump; EM HEAT and

AUX HEAT LEDs; used with T874G1071. Y594G1674a

Table 9. Q674 Subbase Cross Reference.

Model

Number Fig.

No. Description Q674 Trade

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

81 60-2485—8

J1068 144 Obsolete. Carrier heat pump; part no. HH93AZ183;

used with T874J1002

(

HH07AT175

)

or T874J1028

(

HH07AT165

)

Y594J1019

J1076 180 Obsolete. McQua

part no. 02005964; two LEDs; used

with T874A,D. Q674F1022 Replacement has no LEDs.

J1084 171 Obsolete. BDP heat pump; part no. 34427DP126,

P272-1879; EM HEAT LED; used with T874J1010. Y594J1019 Wirin

differences

(

old=new

)

W1=W2, F=L.

J1118 196 Obsolete. Carrier heat pump; part no. HH93AZ188;

SUPL HEAT LED; S

stem: SUPL.HT.-ON-OFF; used

with T874G1055

(

HH07AT171

)

Y594G1674 Wirin

differences

(

old=new

)

C=X;Y1=W1;

umper re

uired;

no auto fan in emer

enc

heat.

J1126 160 Obsolete. Luxaire no. 026-00068-000; EM HEAT LED;

used with T874G1568; used in Y594G1351. Y594G1567a

J1142 174 Obsolete. American Standard part no. WY28X0250;

AUX HEAT and EM HEAT LEDs; used with

T874G1675; used in Y594G1443.

Y594G1161a

J1159 206 Obsolete. Carrier heat pump; part no. HH93AZ196;

used with T874J1002

(

HH07AT175

)

or T874J1028

(

HH07AT165

)

Y594J1019

J1167 175 Obsolete. Carrier heat pump; MANUAL, AUTO, HEAT

PUMP and DEFROST LEDs; S

stem: SUPL HEAT-

ON-OFF; used with T874G1717; used in Y507J1201.

Y594G1252aWirin

differences

(

old=new

)

C=X, D=L; replacement has

AUX HEAT and EM HEAT

LEDs.

J1175 216 Obsolete. Sn

der General part nos. 1505756,

1506756; CHECK, AUX HEAT and SYSTEM LEDs;

used with T874G1774, G1782; used in Y594G1500,

G1518.

Y594G1252aWirin

differences

(

old=new

)

E=W2, W1=W3, X=E, C=X.

J1191 161 Obsolete. Carrier heat pump;

color; used with

T874G1790. Y594G1252aWirin

differences

(

old=new

)

C=X; replacement has °F

scaleplate.

J1209 160 TRADELINE; desi

ned to replace Y594G1013

(

York

part no. 2TH11702424

)

, Y594G1229

(

York part no.

6TH11702424

)

and York part no. 2TH11704124; used

with T874G1865; used in Y594G1567.

Y594G1567a

J1217 171 Obsolete. Nord

ne part no. 9132250; used with

T874J1036, J1044. Y594J1019 Wirin

differences

(

old=new

)

F=L.

J1225 160 Obsolete. TRADELINE;

color; desi

ned to replace

Y594G1013

(

York part no. 2TH11702424

)

, Y594G1229

(

York part no. 6TH11702424

)

and York part no.

2TH11704124; used with T874G1873; used in

Y594G1575.

Y594G1567aReplacement is bei

J1241 144 Obsolete. Carrier Canada part no. HH93AZ183-W;

color; S

stem: SUPL HT-ON-OFF; includes one

LED.

See OEM for

replacement.

J1258 161 Obsolete. Carrier Canada part no. HH93AZ173-W;

color; S

stem: SUPL HT-ON-OFF; includes one

LED.

Y594G1674aReplacement is bei

e color.

J1266 160 York Canada;

color; includes EM HT LED; used in

Y594G1625. Y594G1567a

J1274 161 TRADELINE; S

stem: SUPL HT-ON-OFF; includes

one LED; used with T874G2004; used in Y594G1674. Y594G1674

J1282 244 Obsolete. TRADELINE; S

stem: SUPL HT-ON-OFF;

includes SUPL HT LED; used with T874J1069; used in

Y594J1019.

(

Recontrol

)

T8511G1021

Table 9. Q674 Subbase Cross Reference.

Model

Number Fig.

No. Description Q674 Trade

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—882

Q674K S

stem: OFF-HEAT-AUTO-COOL; Fan: None

K1000 93 Obsolete. Carrier part no. HH93AZ172; RC-RH

umper. Q674E1049 Fan switch is not operational.

K1018 95 Obsolete. Oneida Heater part no. 3040284-02;

stem: OFF-WOOD-WOOD/OIL-OIL; used with

T874F1106.

Q674K1026

K1026 95 S

stem: OFF-WOOD-WOOD/ OIL-OIL; used with

T874F1155. Q674K1026

K1034 93 Obsolete. Sn

der General part no. 4ELN-7920. Q674E1049 Fan switch is not operational.

K1042 93 Obsolete. Carrier part no. HH93AZ172-W;

color;

includes removable

umper between RC and RH

terminals.

Q674E1049 Fan switch is not operational.

Q674L S

stem: EM.HT.-HEAT-OFF-COOL; Fan: ON-AUTO

L1017 101 Obsolete. York heat pump; EM HEAT LED; coolin

mode chan

eover; compressor lockout; auto fan in

EM.HT; used with T874R1046.

Y594R1243aWirin

differences

(

old=new

)

W=W2, X=L, B=X.

L1025 102 Obsolete. Lennox heat pump; part no. 24F6101; EM.

HEAT LED; V-VR

umper; used with T874R1020,

J1038.

Y594R1243aWirin

differences

(

old=new

)

M=Y, F=G, V-VR=VR, Y=W2,

R=O.

L1033 115 Obsolete. Rheem heat pump; EM HEAT LED; used

with T874R1152. Y594R1243a

L1041 103 Obsolete. Carrier heat pump; part no. HH93AZ175;

SUPL HEAT LED; used with T874G1055

(

HH07AT171

)

, G1071

(

HH93AZ175

)

, G1113.

Y594G1419 Wirin

differences

(

old=new

)

C=X,

umper Y1=W1.

L1066 122 Obsolete. Fedders heat pump; used with T874R1269;

used in Y594R1037. Y594R1615aWirin

differences

(

old=new

)

K=E, C=X, W1=B, Z=L.

L1074 124 Obsolete. Carrier heat pump; part no. HH93AZ186;

SUPL HT LED; used with T874J1002

(

HH07AT175

)

T874J1028

(

HH07AT165

)

Y594J1001

L1082 104 Obsolete. Crispaire heat pump; W2-H

umper; EM

HEAT LED; used with T874R1061, R1111. Y594R1243aReplacement has auto fan in

emer

enc

heat mode.

L1090 105 Obsolete. Fedders heat pump; EM HEAT LED;

chan

eover in heat mode; used with T874C1398,

C1406, C1414.

Y594R1425aWirin

differences

(

old=new

)

K=E, C=X.

L1108 106 Obsolete. Westin

house; EM HEAT LED. Y594R1243a

L1116 107 Obsolete. Carrier part no. HH93AZ171; SUPL HEAT

LED; used with T874D1264

(

HH07AT173

)

.See OEM for

replacement.

L1132 108 Heil Quaker part no. HQ711598; used with T874R1137,

R1673, R1731, R1749, R1814; used in Y594R1110,

R1466, R1524, R1532, R1607.

Y594R1292a

L1140 109 Obsolete. Includes EM HEAT and AUX HEAT LEDs;

used with T874R1053; used in Y594G1136. Y594R1763aDesi

ned for use on Trane

heat pumps.

L1157 115 Obsolete. Rheem part no. 41-20796-14; EM HEAT and

AUX HEAT LEDs; used with T874R. Q674L1207a

121 Obsolete. Used with T874C. Y594C1322a

123 Obsolete. Used with T874R. Y594R1243a

L1165 110 Obsolete. Lennox no. 24F5901; factor

installed V-VR

umper; EM HEAT and SERVICE LEDs; sta

e 2 heat is

isolated; used with T874C1448, R1178 and

C815A1013.

Y594R1763aWirin

differences

(

old=new

)

V-VR=R, M=Y, F=G, X=B,

Y=W, A=T, R=O, E=X2.

L1173 112 Obsolete. Westin

house; AUX HEAT and EM HEAT

LEDs. Y594R1243a

Table 9. Q674 Subbase Cross Reference.

Model

Number Fig.

No. Description Q674 Trade

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

83 60-2485—8

L1181 113 Used with T874R1129; used in Y594R. Y594R1243aWirin

differences

(

old=new

)

X1=X.

L1199 114 Obsolete. Lennox no. 24F6001; used with T874D1207

and C815A1013. T8611M2025

(

pro

rammable

)

Wirin

differences

(

old=new

)

V-VR=R, Y=W3, X=C, R=O,

M=Y, M2=Y2-W2, F=G;

umper Y2-W2; no outdoor

reset needed; use onl

one

stem transformer.

L1207 115 Used with T874R1152, R1590, R1640, R1921; used in

Y594R1243, R1706. Q674L1207 or

Y594R1243a

L1215 116 Obsolete. Crispaire heat pump; used with T874R1111;

used in Y594R1128. Y594R1243aReplacement has auto fan in

emer

enc

heat mode. Wirin

differences

(

old=new

)

: A=L;

set anticipator to 1.2.

L1223 117 Obsolete. Westin

house special. See OEM for

replacement.

L1231 182 Obsolete. Used with T874R1186 and W89. None

L1249 115 Obsolete. Used with T874R1194 and W89. Y594R1243a

L1256 118 Obsolete. Westin

house special; used with

T874W1007. T8611M2025

(

pro

rammable

)

Includes ni

ht setback.

L1264 119 Obsolete. Intertherm heat pump; EM HEAT and SERV

LEDs; used with T874R1202, R1608, R1699; used in

Y594R1185, R1409, R1482.

Y594R1672a or

Y594R1763a

Wirin

differences

(

old=new

)

W2=W, X=B, Z=no

connection, K=X, W1=H.

L1272 120 Obsolete. York part no. 025-22290; used with

T874R1046, R1145; used in Y594R1011, R1102; used

with T874R1228, R1251 R1327 and C815A1039; used

in Y594R1144, R1151, R1193.

Y594R1672a

L1280 233 Obsolete. Lennox no. 52C7601; used with T874W1023

and W89. Y594W1014a

L1298 182 Obsolete. Sin

er heat pump; used with T874R1160

and W89. See OEM for

replacement.

L1314 115 Obsolete. Westin

house heat pump; used with

T874R1244 and W89. Q674L1207 or

Y594R1243a

L1322 127 Obsolete. EM HEAT and AUX HEAT LEDs; used with

T874C1455. Y594R1243a

L1330 120 Obsolete. York heat pump; used with T874R. Y594R1664aWirin

differences

(

old=new

)

L=X, X=B.

L1348 115 Obsolete. Williamson heat pump; used with

T874R1236. Q674L1207

L1355 111,

190 Obsolete. Lennox part no. 31F3201; V-VR

umper;

used with T874C1448, R1178 and C815A1015. Y594R1763aWirin

differences

(

old=new

)

V-VR=R, M=Y, F=G, X=B,

Y=W, A=T, R=O, E=X2.

L1363 129 Obsolete. York heat pump; EM HEAT LED; used with

T874G1402. Y594R1425aWirin

differences

(

old=new

)

W=W2, X=E, B=X;

umper Y-

W1.

L1371 124 Obsolete. BDP heat pump; part no. 34427DP125,

P272-1878; EM HEAT LED; used with T874J1010. Y594J1001 Wirin

differences

(

old=new

)

W1=W2, F=L.

L1389 114 Obsolete. Lennox part no. 41F6501; V-VR

umper;

used with T874D1207. T8611M2025

(

pro

rammable

)

Wirin

differences

(

old=new

)

V-VR=R, Y=W3, X=C, R=O,

M=Y, M2=Y2-W2, F=G;

umper Y2-W2; no outdoor

reset needed; use onl

one

stem transformer.

Table 9. Q674 Subbase Cross Reference.

Model

Number Fig.

No. Description Q674 Trade

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—884

L1397 103 Obsolete. Carrier part no. HH93AZ185A; SUPL HEAT

LED. Y594G1393aWirin

differences

(

old=new

)

C=X.

L1405 106 Obsolete. BDP heat pump; part no. HH641501; used

with T874R1335; used in Y594R1201. Y594R1243a

L1413 133 Obsolete. Fedders heat pump; used with T874R1343;

used in Y594R1219. Y594R1425aWirin

differences

(

old=new

)

K=E, C=X, Z=L; remove

W1-Y

umper.

L1421 125 Obsolete. Coleman heat pump; used with T874R1368;

used in Y594R1235. Y594R1797a

L1439 131 Obsolete. Carrier part no. HH93AZ187; SUPL HEAT

LED; S

stem: SUPL HT-HEAT- COOL; used with

T874R1384

(

HH07AQ170

)

Q674L1207 or

Y594G1393a

Wirin

differences

(

old=new

)

C=X.

L1447 128 Obsolete. Williamson heat pump; three LEDs; used

with T874R1392; used in Y594R1250. Y594R1425aWirin

differences

(

old=new

)

A=L.

L1454 131 Obsolete. Carrier part no. HH93AZ197; SUPL HEAT

LED; used with T874R1384

(

HH07AQ170

)

.Y594R1393aWirin

differences

(

old=new

)

C=X.

L1462 113 Obsolete. LSI heat pump; part no. 104710002; used

with T874R1400. Y594R1243aWirin

differences

(

old=new

)

X1=X.

L1496 136 Obsolete. Trane heat pump; used with T874R1426;

used in Y594R1284. Y594R1763a

L1504 134 Rheem part no. 41-20796-24; used with T874R1442,

R1434, R1459; used in Y594R1631, R1649, R1854. Y594R1300a

L1512 108 Includes two LEDs; used with T874R1467; used in

Y594R1292. Y594R1292a

L1520 123 Includes EM HEAT and AUX HEAT LEDs; used with

T874R1475; used in Y594R1300. Y594R1300a

L1538 130 Obsolete. Sn

der General heat pump; used with

T874R1483, R1517, R1566 and C815A1005; used in

Y594R1318, R1342, R1375.

Y594R1763aWirin

differences

(

old=new

)

C=B, W1=W, E=X2, X=F.

132 Obsolete. Used with T874R1574, R1582; used in

Y594R1383, R1391. Y594R1243aWirin

differences

(

old=new

)

C=X, X=L, W=W2.

L1546 140 Obsolete. Rheem part no. 41-20797-21; three LEDs;

used with T874W1031 and C815A1005; used in

Y594W1022.

T8611M2025

(

pro

rammable

)

Includes ni

ht setback.

L1553 137 Obsolete. Includes three LEDs; used with T874R1491;

used in Y594R1326. Y594R1615a

L1561 121 Obsolete. Used with T874C1638; used in Y594C1322. Y594C1322aUse Y594C1322 when T874C

is used.

123 Obsolete. Used with T874R. Y594R1243aUse Y594R1243 when T874R

is used.

L1579 135 Obsolete. Carrier heat pump; part no. HH93AZ198;

SUPL HEAT LED; used with T874R1384

(

HH07AQ170

)

Y594R1243aWirin

differences

(

old=new

)

C=X.

L1587 168 Used with T874R1616; used in Y594R1425. Y594R1425a

L1595 200,

201 Obsolete. Miller heat pump; used with T874R1624 or

T874R1202; used in Y594R1433. Y594R1243a or

Y594R1763a

L1603 134 Obsolete. Used with T874R1632. Y594R1243a

L1611 136 Obsolete. American Standard heat pump; part no.

WY28X235; used with T874R1657; used in

Y594R1441.

Y594R1763a

Table 9. Q674 Subbase Cross Reference.

Model

Number Fig.

No. Description Q674 Trade

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

85 60-2485—8

L1637 207 Obsolete. Carrier heat pump; part no. HH93AZ195;

used with T874J1002

(

HH07AT175

)

or T874J1010

(

HH07AT165

)

Y594J1001a

L1678 209 Trol-A-Temp b

Hone

well;

color; used with

T874R1707; used in Y594R1490. None See Trol-A-Temp.

L1686 209 Trol-A-Temp b

Hone

well; used with T874R1715;

used in Y594R1508. None See Trol-A-Temp.

L1702 132 Obsolete. Sn

der General heat pump; part no.

654958B07; used with T874R1723 and C815A1005;

used in Y594R1516.

Y594R1672aWirin

differences

(

old=new

)

C=B, W1=W, X=X2.

L1710 230 Used with T874R1822; used in Y594R1615. Y594R1615a

L1728 228 Obsolete. Lennox;

color; used with T874R1855;

used in Y594R1714. Y594R1763aWirin

differences

(

old=new

)

Y1=Y, L=F, W1=W, E=X2, C=B.

L1736 120 Desi

ned to replace Y594R1011

(

York part no.

2TH11702224

)

; used with T874R1871; used in

Y594R1664.

Y594R1664a

Desi

ned to replace Y594R1151

(

York part no.

2TH11702324

)

, Y594R1193

(

York part no.

6TH11702224

)

and York part no. 2TH11704024; used

with T874R1889 and C815A1054; used in Y594R1672.

Y594R1672a

L1751 230 Gra

color; used with T874R1897, used in

Y594R1680. Y594R1680a

L1769 124 Obsolete. Nord

ne part no. 9132260; used with T874J. See OEM for

replacement.

L1777 120 Obsolete. Gra

color; desi

ned to replace Y594R1151

(

York part no. 2TH11702324

)

, Y594R1193

(

York part

no. 6TH11702224

)

and York part no. 2TH11704024;

used with T874R1905 and C815A1059; used in

Y594R1698.

Y594R1672aReplacement is bei

Desi

ned to replace Y594R1011

(

York part no.

2TH11702224

)

; used with T874R1913; used in

Y594R1706.

Y594R1664aReplacement is bei

L1785 103 Obsolete. Carrier part no. HH93AZ175-W; Canada;

color; S

stem: Supl Ht-Heat-Off-Cool; includes

one LED.

Y594G1476aWirin

differences

(

old=new

)

C=X; Y1-W1

umper re

uired.

L1793 124 Obsolete. Carrier Canada part no. HH93AZ186-W;

color; Fan: Auto-On; S

stem: Supl Ht-Heat-Off-

Cool; includes one LED.

Y594J1019a

L1801 197 American Standard

(

Trane

)

part no. THT1225; includes

two LEDs; used with T874R1939; used in Y594R1748. Y594R1763a

L1819 168 Obsolete. Inter-Cit

Products part no. HQ1149407HW;

includes three LEDs; used with T874R1947; used in

Y594R1755.

Y594R1425a

L1827 197 TRADELINE; includes two LEDs; used with

T874R1954; used in Y594R1763; direct replacement

for Trane/American Standard Y594R1748

(

T874R1939/Q674L1801

)

Trane part no. ASYSTAT

631A, Y594R1136

(

T874R1053/Q674L1140

)

Y594R1763a

L1835 140 Obsolete. Inter-Cit

Products; includes three LEDs;

used in Y594W1030. T8611M2025a

(

pro

rammable

)

Includes ni

ht setback.

L1843 115 Obsolete. Consolidated Industries part no. 9036100;

color; includes two LEDs; used with T874R1962;

used in Y594R1771.

Y594R1680aIncludes CHECK LED.

Table 9. Q674 Subbase Cross Reference.

Model

Number Fig.

No. Description Q674 Trade

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—886

L1850 120 York Canada;

color; includes one LED; used with

T874R1970; used in Y594R1789. Y594R1672a

L1868 125 TRADELINE; includes two LEDs; used with

T874R1988; used in Y594R1797; direct replacement

for Evcon/Coleman Y594R1235

(

T874R1368/

Q674L1421

)

Coleman part no. 3600-368.

Y594R1797a

L1876 245 Obsolete. Amana part no. 10573902; includes two

LEDs; used with T874R2002; used in Y594R1805. Y594R1797 Wirin

differences

(

old=new

)

C/X=X.

L1884 245 Obsolete. Amana part no. 10573904; includes two

LEDs; used with T874R2010; used in Y594R1813. Y594R1797 Wirin

differences

(

old=new

)

C/X=X, W3=W2.

L1892 103 Obsolete. TRADELINE; S

stem: SUPL HT-HEAT-

OFF-COOL; includes one LED; used with T874G2004;

used in Y594G1666; direct replacement for Carrier

Y507J1011

(

T874G1055/Q674L1041

)

Carrier part no.

HH07AT171/HH93AZ175.

Y594G1674 Replacement has auto

chan

eover.

L1900 241 Obsolete. TRADELINE; S

stem: SUPL HT-HEAT-

OFF-COOL; includes SUPL HT LED; used with

T874J1069; used in Y594J1001; direct replacement for

Carrier T874J1028/Q674J1068

(

Carrier part no.

HH07AT165/HH93AZ183

)

, Carrier T874J1002/

Q674J1068

(

Carrier part no. HH07AT175/

HH93AZ183

)

Y594J1019 Replacement has auto

chan

eover.

L1918 125 Obsolete. York lo

o; part no. 2TH11703424A; includes

two LEDs; used with T874R2028 in Y594R1821. Y594R1797a

L1934 123 Obsolete. Addison lo

o; part no. 843-277; includes

three LEDs; used with T874W1106 in Y594W1055. T8611M2025

Q674N S

stem: OFF-HEAT-COOL-EVAP; Fan: AUTO-ON

N1015 60 Obsolete. Goettl heat pump; chan

eover in heat mode;

evaporative cooler circuit; used with T874C1182. See OEM for

replacement.

N1023 61 Obsolete. Si

ler heat pump; evaporative cooler circuit;

used with T874C1349. See OEM for

replacement.

Q674P S

stem: SUPL HT-HEAT-COOL; Fan: AUTO-ON

P1005 126 Obsolete. Carrier heat pump; part no. HH93AZ169;

used with T874G1071

(

HH07AT171

)

.Y594G1419aWirin

differences

(

old=new

)

C=X;

umper Y1-W1;

replacement has OFF-EM HT-

HEAT-AUTO-COOL s

stem

switchin

Q674Q S

stem: HEAT-OFF-COOL; Fan: LOW-MED-HI-ON

Q1004 59 Obsolete. McQua

special; used with T874A1267. See OEM for

replacement.

Q1012 64 Used with T874A1291. None

Q674R S

stem: OFF-COOL; Fan: LO-HI-CONT

R1003 69 Obsolete. Carrier part no. HH93AZ190; international

mbols on fan and switches; used with T874V1008

(

HH07AT177

)

See OEM for

replacement.

Q674S S

stem: HEAT-COOL; Fan: None

S1000 70 Obsolete. Fiber

las; Canada; SERVICE LED; used

with T874C1653; used in Y594C1348. See OEM for

replacement.

Q674W S

stem: OFF-ON; Fan: LO-MED-HI

W1006 240 Obsolete. Sn

der General part no. 044271801. See OEM for

replacement.

Table 9. Q674 Subbase Cross Reference.

Model

Number Fig.

No. Description Q674 Trade

Replacement Remarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

87 60-2485—8

Table 10. Y594 Cross Reference.

Model

Number Fig.

No. Description Trade Model

ReplacementaRemarks

Y594A

A1001 46 Obsolete. Amana part no. D68535-11; contains

T874A1077, Q674B1075. T874A1036/

Q674B1075

A1019 82 Obsolete. Amana part no. P68535-12; contains

T874A1077, Q674E1056. T874A1036/

Q674E1049

A1035 44 Obsolete. Trane part no. 268-0187-1; contains

T874A1085, Q674B1018. T874A1036/

Q674B1018

A1043 46 Obsolete. Trane part no. 268-0201-5; contains

T874A1085, Q674B1075. T874A1036/

Q674B1075

A1050 55, 66 Obsolete. Trane part no. 268-0201-3; contains

T874A1085, Q674D1008. T874A1036/

Q674D1040

A1068 82 Obsolete. Sears part no. 42-9144; contains

T874A1119, Q674E1007. T874A1036/

Q674E1049

A1126 64 Contains T874A1291, Q674Q1012. None

A1159 91 Obsolete. Contains T874A1440, Q674G1005. T874A1150/

Q674G1070

A1167 184 California Economizer; Premier White® color;

contains T874A1580 and Q674G1161. T874A1036/

Q674G1070 Replacement is bei

e color.

A1175 55 Obsolete. York lo

o; part no. 2TH04703224;

contains T874A1622, Q674D1180. T874A1010/

Q674D1040

A1191 46 Obsolete. Amana lo

o: part no. P6853524R;

contains T874A1002, Q674B1075. T874A1036/

Q674B1075

Y594B

B1026 44 Trane part no. BAYSTAT012; contains T874B1035,

Q674B1018. T874B1019/

Q674B1018

B1034 46 Obsolete. Trane part no. 163-552-1; contains

T874B1035, Q674B1075. T874B1019/

Q674B1075

B1042 88 Obsolete. Goodman part no. CHTS36-60; contains

T874B1100, Q674E1338. T874B1019/

Q674E1049 No LEDs on replacement.

Y594C

C1009 82 Obsolete. Amana part no. D68535-9; contains

T874C1059, Q674E1056. T874C1018/

Q674E1049 Jumper RC-RH.

C1017 142 Obsolete. Amana part no. D68535-10; contains

T874C1059, Q674F1022. T874C1018/

Q674F1022

C1058 46 Obsolete. Contains T874C1000, Q674B1075. T874C1018/

Q674B1075

C1082 82 Obsolete. Trane part no. 166-162-1; contains

T874C1083, Q674E1007. T874C1018/

Q674E1049

C1256 45 Obsolete. Amana part no. D68535-16; contains

T874C1059, Q674B1059. T874C1018/

Q674B1034 Jumper RC-RH.

C1280 45 Obsolete. Williamson; contains T874C1570,

Q674B1000. T874C1018/

Q674B1034

C1314 56 Obsolete. LSI; contains T874C1471, Q674B1257. T874C1018/

Q674B1018 Jumper RC-RH; no RESET

LED on replacement.

C1322 121 Obsolete. Contains T874C1638, Q674L1561. Y594C1322

C1330 142 Obsolete. Amana part no. D68535-21; contains

T874C1059, Q674F1022. T874C1018/

Q674F1022

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—888

C1348 70 Obsolete. Fiber

las; contains T874C1653,

Q674S1000. T874C1000/

Q674B1075 Wirin

differences

(

old=new

)

Y=Y1;

umper RC-RH and Y1-

W1; replacement has no

SERVICE

LED; replacement

has fan switchin

and HEAT-

OFF-COOL s

stem switchin

C1355 45 Obsolete. Nord

ne “Miller” part no. 9122250;

contains T874C1695, Q674B1000. T874C1018/

Q674B1034

C1363 45 Obsolete. Nord

ne “Intertherm” part no. 911100001;

contains T874C1703, Q674B1000. T874C1018/

Q674B1075 Wirin

differences

(

old=new

)

Y=Y1;

umper RC-RH; Y1-W;

replacement has no SERVICE

LED.

C1371 184 Obsolete. California Economizer; contains

T874C1802 and Q674G1005. T874C1018/

Q674G1070

C1389 237 Obsolete. TRADELINE; Premier White® color;

contains T874C1810 and Q674B1547. Y594C1389

C1413 238 Heat Controller “Ener

ht” lo

o; contains

T874C1844 and Q674F1592. Y594R1425 E-W2

umper re

uired; s

stem:

EM.HT.-Heat-Off-Cool.

C1421 249 Obsolete. TRADELINE; contains T874C1877 and

Q674B1554. Y594D1347 Replacement has auto

chan

eover;

umper RH-RC.

C1439 T874C1869 and Q674C1579. None

Y594D

D1016 44 Obsolete. Trane part no. 268-0201-2; contains

T874D1082, Q674B1018. T874D1165/

Q674B1018

D1024 72 Trane part no. BAYSTAT010; contains T874D1082,

Q674C1009. T874D1165/

Q674C1058

D1032 91 Obsolete. Trane part no. BAYSTAT011; contains

T874D1082, Q674G1021. T874D1165/

Q674G1070

D1040 46 Amana part no. P68535-19R; contains T874D1082,

Q674B1075. T874D1165/

Q674B1075

D1057 55, 66 Obsolete. Trane part no. BAYSTAT007; contains

T874D1082, Q674D1008. T874D1165/

Q674D1040

D1149 46 Obsolete. Amana part no. P68535-20C; contains

T874D1322, Q674B1075. T874D1165/

Q674B1075

D1156 48 Obsolete. Trane part no. BAYSTAT013; contains

T874D1082, Q674B1133. T874D1165/

Q674B1018 Replacement has no FILTER

LED.

D1180 82 York part no. 025-23321-000; contains T874D1504,

Q674E1007. T874D1165/

Q674E1049

D1222 166 Obsolete. WeatherKin

; contains T874D1009,

Q674F1337. T874D1165/

Q674F1022 Wirin

differences

(

old=new

)

R=RH;

umper RC-RH;

replacement has no EM.HT. or

AUX. HT. LEDs.

D1248 82 Obsolete. Reznor part no. 93437; contains

T874D1629, Q674E1007. T874D1165/

Q674E1049

D1297 82 Obsolete. ArcoAire part no. 1506753; contains

T874D1769, Q674E1346. T874D1165/

Q674E1049

D1305 82 Obsolete. Comfortmaker part no. 1505753; contains

T874D1785, Q674E1346. T874D1165/

Q674E1049

D1321 45 Obsolete. Goodman part no. CHT 90-120; contains

T874D1843, Q674B1000. T874D1165/

Q674B1034

D1339 82 Obsolete. Nord

ne part no. 5471180; contains

T874D1009, Q674E1007. T874D1165/

Q674E1049

Table 10. Y594 Cross Reference.

Model

Number Fig.

No. Description Trade Model

ReplacementaRemarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

89 60-2485—8

D1347 82 TRADELINE® contains T874D1942, Q674E1403. Y594D1347

D1354 82 SUPER TRADELINE® contains T874D2031

(

cover

)

, Q674E1049, and TG504A with two ke

s. Y594D1354

D1370 45 Obsolete. Carrier part no. 50QE90022101; contains

T874D2049 and Q674B1539. T874D1165/

Q674B1034 Replacement has °F

scaleplate.

D1388 72 Obsolete. Carrier part no. 50QE90023101; contains

T874D2049 and Q674C1520. T874D1165/

Q674C1058 Replacement has °F

scaleplate.

D1396 184 Obsolete. Carrier part no. 50QE90025101; contains

T874D2049 and Q674G1153. T874D1165/

Q674G1070 Replacement has °F

scaleplate.

D1404 55, 66 Obsolete. Carrier part no. 50QE90024101; contains

T874D2049 and Q674D1164. T874D1165/

Q674D1040 Replacement has °F

scaleplate.

D1412 82 Obsolete. Carrier “Weathermaker” part no.

HH07AT209; taupe color; contains T874D2064 and

Q674E1445.

T874D1165/

Q674E1049 Replacement is bei

e color.

D1420 82 Obsolete. Carrier “Zone Perfect” part no.

HH07AT208; taupe color; contains T874D2072 and

Q674E1445.

T874D1165/

Q674E1049 Replacement is bei

e color.

D1438 55, 66 Obsolete. Contains T874D2098 and Q674D1008. T874D1165/

Q674D1040 Replacement has 2 setpoint

levers.

D1446 55, 66 Obsolete. Contains T874D2106 and Q674D1008. T874D1165/

Q674D1040 Replacement has °F

scaleplate and 2 setpoint

levers.

D1453 208 Obsolete. Amana lo

o; part no. P1217501F;

contains T874D2163 and Q674D1172. T874D1165/

Q674D1040

D1461 45 Obsolete. Amana lo

o; part no. P1217701F;

contains T874D2171 and Q674B1562. T874D1942/

Q674B1034

Y594E

E1015 72 Obsolete. Trane part no. BAYSTAT015; contains

T874E1040, Q674C1009. T874B1019/

Q674C1058

Y594F

F1022 44 Obsolete. Contains T874F1031 and 40003440-001

wallplate with installed diode. T874F1015

F1048 72 Obsolete. Reznor part no. 93436; contains

T874F1130, Q674C1009. T874F1015/

Q674C1058

F1063 91 Obsolete. Reznor part no. 93435; contains

T874F1130, Q674G1005. T874F1015/

Q674G1070

Y594G

G1013 160 Obsolete. York part no. 2TH11702424; contains

T874G1170, Q674J1027. Y594G1567

G1138 160 Obsolete. York part no. 025-22286; contains

T874G1196, Q674J1027. Y594G1567

G1153 154 Obsolete. Crispaire part no. HP10-51; contains

T874G1089, Q674F1204. Y594G1252 Wirin

differences

(

old=new

)

A=L.

G1161 162 Contains T874G1204, Q674J1043. Y594G1161

G1195 155 Obsolete. Heil Quaker part no. HQ521387HW;

contains T874G1246, Q674F1212. Y594G1252

G1229 160 Obsolete. York part no. 6TH11702424; contains

T874G1428, Q674J1027. Y594G1567

G1245 155 Obsolete. BDP part no. HH641502; contains

T874G1451, Q674F1212. Y594G1252

G1252 155 TRADELINE; contains T874G1246, Q674F1212. Y594G1252

Table 10. Y594 Cross Reference.

Model

Number Fig.

No. Description Trade Model

ReplacementaRemarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—890

G1294 79 Obsolete. LSI; contains T874G1378, Q674C1124. See OEM for

replacement. H2 is ni

ht setback.

G1328 194 Obsolete. Addison part no. 8403-197; contains

T874G1543, Q674F1345. Y594G1252 Wirin

differences

(

old=new

)

Y1=O, X=L, C=X.

G1344 194 Obsolete. Heat Controller part no. 7601-110B;

contains T874G1469, Q674F1345. Y594G1252 Wirin

differences

(

old=new

)

Y1=O, X=L, C=X; W1=Y.

G1351 160 Obsolete. Luxaire part no. 026-00068-000; contains

T874G1568, Q674J1126. Y594G1567

G1369 155 Obsolete. Contains T874G1246, Q674F1212. Y594G1252

G1377 169 Obsolete. Coleman part no. 3600-373; contains

T874G1576, Q674F1402. Y594G1633

G1385 155 Obsolete. ArcoAire; contains T874G1592,

Q674F1212. Y594G1252

G1393 170 Obsolete. Contains T874R1393, Q674L1454. Y594G1393

G1419 227 TRADELINE; contains T874G1642, Q674F1444. Y594G1419

G1427 177 Obsolete. Mammoth part no. 73034101; contains

T874G1659, Q674C1330. See OEM for

replacement. H2 is ni

ht setback.

G1443 174 Obsolete. American Standard

(

Trane

)

part no.

ASYSTAT650; contains T874G1675, Q674J1142. Y594G1161

G1476 227 TRADELINE; same as Y594G1419 except Premier

White® color; contains T874G1741, Q674F1477. Y594G1476

G1492 211 Trol-A-Temp; contains T874G1758, Q674F1485. None See Trol-A-Temp for

replacement.

G1500 216 Obsolete. Comfortmaker part no. 1505756; contains

T874G1774, Q674J1175. See OEM for

replacement.

G1518 216 Obsolete. ArcoAire part no. 1506756; contains

T874G1782, Q674J1175. See OEM for

replacement.

G1526 167 TRADELINE; contains T874G1626, Q674F1436. None

G1534 227 TRADELINE; °C; white; Australia; contains

T874G1824, Q674F1477. None

G1542 231 Obsolete. Intertherm part no. 9129290; contains

T874G1832, Q674F1519. Y594G1252 Coolin

chan

eover onl

G1559 231 Obsolete. Miller part no. 9129310; contains

T874G1840, Q674F1519. Y594G1252 Coolin

chan

eover onl

G1567 160 TRADELINE; contains T874G1865, Q674J1209. Y594G1567

G1575 160 Obsolete. TRADELINE; same as Y594G1567

except Premier White® color; contains T874G1873,

Q674J1225; direct replacement for York

2TH11702424

(

Y594G1013 contains T874G1170/

Q674J1027

)

and 6TH11702424

(

Y594G1229

contains T874G1428/Q674J1027

)

Y594G1567 Replacement is bei

G1583 229 Obsolete. Lennox Canada part no. 97E78; contains

T874G1857, Q674F1535. Y594G1161 Wirin

differences

(

old=new

)

E=X2, C=B, L=F.

G1591 243 Obsolete. Amana part no. 10636701; contains

T874G1899 and Q674F1550. Y594G1633

G1609 155 Obsolete. Econar; contains T874G1915 and

Q674F1212. Y594G1252

Table 10. Y594 Cross Reference.

Model

Number Fig.

No. Description Trade Model

ReplacementaRemarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

91 60-2485—8

G1617 73 Obsolete. Carrier part no. 50QE90020101; contains

T874G1949 and Q674C1504. Y594H1012aWirin

differences

(

old=new

)

Y1=O, Y2=Y, L=R, R=none;

R-L

umper re

uired; no ni

setback.

T8600D2028

(

pro

rammable

)

Wirin

differences

(

old=new

)

Y1=O, Y2=Y, L=R; W-Y

umper

uired; ni

ht setback.

G1625 160 York Canada part no. 2TH11702524; contains

T874G1964 and Q674J1266. Y594G1567aReplacement has °F

scaleplate.

G1633 169 TRADELINE; contains T874G1972 and

Q674F1584; direct replacement for Y594G1377

(

T874G1576/Q674F1402

)

Evcon/Coleman part no.

3600-373.

Y594G1633a

G1641 169 Obsolete. Amana part no. 10636703; contains

T874G1980 and Q674F1600. Y594G1633 Wirin

differences

(

old=new

)

W3=W2.

G1658 155 Obsolete. Tempstar “Inter-Cit

Products” part no.

1149910; contains T874G1998 and Q674F1212. Y594G1252

G1666 103 Obsolete. TRADELINE; manual chan

eover;

contains T874G2004 and Q674L1892; direct

replacement for Y507J1011

(

T874G1055/

Q674L1041

)

Carrier part no. 99TZ90041106

(

HH07AT171/HH93AZ1750

)

Y594G1674 Replacement has auto

chan

eover.

G1674 161 TRADELINE; automatic chan

eover; contains

T874G2004 and Q674J1274; direct replacement

Y507J1003

(

T874G1055/Q674J1035

)

Carrier part

no. 99TZ90040106

(

HH07AT171/HH93AZ173

)

Y594G1674

G1716 155 WaterFurnace lo

o; part no. TA21H03; contains

T874G2046 and Q674F1667. Y594G1716

Y594H

H1004 79 Obsolete. LSI part no. 73033901; contains

T874H1039 and Q674C1124. T8600D2028 H2 is ni

ht setback.

H1012 164 Contains T874H1062 and Q674C1249; replaces

T874H1005/Q674C1041. Y594H1012

H1020 177 Obsolete. Mammoth part no. 71117101; contains

T874H1096 and Q674C1330. Y594H1012 Wirin

differences

(

old=new

)

R1=R, R2=L; use

umper

provided.

H1038 74 Obsolete. Carrier part no. 50QE90019101; contains

T874H1161 and Q674C1496. Y594H1012aWirin

differences

(

old=new

)

X1=O, Y2=Y; L-R

umper

uired.

H1046 172 Obsolete. Carrier part no. 50QE90026101; contains

T874H1153 and Q674B1406. T874A1130/

Q674B1075a

Wirin

differences

(

old=new

)

Y=Y1; W1-Y1

umper re

uired;

replacement has no LEDs.

H1053 173 Obsolete. Carrier part no. 50QE90027101; contains

T874H1153 and Q674C1322. Y594H1012aWirin

differences

(

old=new

)

Z=X.

Y594J

J1001 241 Obsolete. TRADELINE; manual chan

eover;

contains T874J1069 and Q674L1900; direct

replacement for T874J1002 or T874A1028 used

with Q674L1074 or Q674L1637

(

HH07AT175 or

HH07AT165 used with HH93AZ186 or

HH93AZ195

)

(

Recontrol

)

T8511G1021

Table 10. Y594 Cross Reference.

Model

Number Fig.

No. Description Trade Model

ReplacementaRemarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—892

J1019 244 Obsolete. TRADELINE; automatic chan

eover;

contains T874J1069 and Q674J1282; direct

replacement for T874J1002 or T874J1028 used

with Q674J1068 or Q674J1159

(

HH07AT175 or

HH07AT165 used with HH93AZ183 or

HH93AZ196

)

(

Recontrol

)

T8511G1021

Y594N

N1007 178 Obsolete. Williamson part no. 75-189; contains

T874N1008 and Q674F1196. T874N1016/

Q674F1196

N1015 179 Obsolete. Contains T874N1040 and Q674F1261. Y594G1419aWirin

differences

(

old=new

)

L=X2, Y=Y1.

N1023 178 Obsolete. Intertherm part no. 9111882; contains

T874N1057 and Q674F1220. T874N1016/

Q674F1220

N1031 178 Obsolete. Nord

ne “Miller” part no. 9122240;

contains T874N1065 and Q674F1220. T874N1016/

Q674F1220

Y594P

P1005 97 Obsolete. Carrier part no. 50QE90021101; contains

T874P1055 and Q674C1512. T8600D2028 Wirin

differences

(

old=new

)

Y=Y1, W=O; Y1-W1

umper

uired.

Y594R

R1011 120 Obsolete. York part no. 2TH11702224; contains

T874R1046 and Q674L1272. Y594R1664

R1029 47 Obsolete. Br

ant; contains T874R1004 and

Q674B1042. Y594R1243 Wirin

differences

(

old=new

)

W1=W2.

R1037 122 Obsolete. Fedders part no. 88-58-00540-001;

contains T874R1269 and Q674L1066. Y594R1615 Wirin

differences

(

old=new

)

K=E, C=X, W1=B, Z=L.

R1102 120 Obsolete. York part no. 025-22285-000; contains

T874R1145 and Q674L1272. Y594R1664

R1110 108 Obsolete. Heil Quaker part no. HQ712004HW;

contains T874R1137 and Q674L1132. Y594R1292

R1128 116 Obsolete. Crispaire part no. HP9-51; contains

T874R1111 and Q674L1215. Y594R1243 Wirin

differences

(

old=new

)

A=L.

R1136 109 Obsolete. Contains T874R1053 and Q674L1140. Y594R1763

R1151 120 Obsolete. York part no. 2TH11702324; contains

T874R1251, Q674L1272 and C815A1039. Y594R1672

R1185 201 Obsolete. Intertherm part no. 9111871; contains

T874R1202 and Q674L1264. Y594R1672 Wirin

differences

(

old=new

)

W2=W, X=B, Z=no

connection, K=X, W1=H.

R1193 120 Obsolete. York part no. 6TH11702224; contains

T874R1327 and Q674L1272. Y594R1664

R1201 106 Obsolete. BDP part no. HH641501; contains

T874R1335 and Q674L1405. Y594R1243

R1219 133 Obsolete. Fedders part no. 88-58-00560-001;

contains T874R1343 and Q674L1413. Y594R1425 Wirin

differences

(

old=new

)

K=E, C=X, Z=L; remove

factor

installed

umper.

R1235 125 Obsolete. Coleman part no. 3600-368; contains

T874R1368 and Q674L1421. Y594R1797

R1243 115 TRADELINE; contains T874R1152 and Q674L1207. Y594R1243

R1250 128 Obsolete. Williamson part no. 75-191; contains

T874R1392 and Q674L1447. Y594R1425 Wirin

differences

(

old=new

)

A=L.

R1284 136 Obsolete. Trane part no. BAYSTAT339; contains

T874R1426 and Q674L1496. Y594R1763

Table 10. Y594 Cross Reference.

Model

Number Fig.

No. Description Trade Model

ReplacementaRemarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

93 60-2485—8

R1292 108 Contains T874R1467 and Q674L1512; replaces

Y594R1110

(

T874R1137/Q674L1132

)

.Y594R1292

R1300 123 Contains T874R1475 and Q674L1520. Y594R1300

R1318 130 Obsolete. Comfortmaker part no. 1505721; contains

T874R1483, Q674L1538 and C815A1005. Y594R1763 Wirin

differences

(

old=new

)

W1=W, E=X2, X=F, C=B.

R1326 137 Obsolete. SUPER TRADELINE; contains

T874R1491 and Q674L1553. Y594R1615

R1334 47 Obsolete. Slant Fin; contains T874R1509 and

Q674B1042. Y594R1243 Wirin

differences

(

old=new

)

W1=W2.

R1342 130 Obsolete. ArcoAire part no. 1506721; contains

T874R1517, Q674L1538 and C815A1005. Y594R1763 Wirin

differences

(

old=new

)

W1=W, E=X2, X=F, C=B.

R1359 113 Obsolete. ArcoAire part no. A02074; contains

T874R1525 and Q674L1181. Y594R1243 Wirin

differences

(

old=new

)

X1=X.

R1375 130 Obsolete. Contains T874R1566, Q674L1538 and

C815A1005. Y594R1763 Wirin

differences

(

old=new

)

W1=W, E=X2, X=F, C=B.

R1383 132 Obsolete. Comfortmaker part no. 1505739; contains

T874R1574 and Q674L1538. Y594R1243 Wirin

differences

(

old=new

)

W=W2, C=X, X=L.

R1391 132 Obsolete. ArcoAire part no. 1506739; contains

T874R1582 and Q674L1538. Y594R1243 Wirin

differences

(

old=new

)

W=W2, C=X, X=L.

R1409 119 Obsolete. Intertherm part no. 6244630; contains

T874R1608 and Q674L1264. Y594R1763 Wirin

differences

(

old=new

)

W2=W, X=B, Z=F, K=X2,

W1=O.

R1417 113 Obsolete. Comfortmaker part no. 1505-735;

contains T874R1301 and Q674L1181. Y594R1243 Wirin

differences

(

old=new

)

X1=X.

R1425 168 SUPER TRADELINE; contains T874R1616 and

Q674L1587. Y594R1425

R1433 200 Obsolete. Miller part no. 9115900; contains

T874R1624 and Q674L1595. Y594R1243 Wirin

differences

(

old=new

)

W2=W, X=B, Z=F, K=X2,

W1=O.

R1441 136 Obsolete. American Standard

(

Trane

)

part no.

ASYSTAT651; contains T874R1657 and

Q674L1611.

Y594R1763

R1466 108 Heil Quaker part no. 1060321; model no.

HAXB004TW01; contains T874R1673 and

Q674L1132.

Y594R1292

R1482 119 Obsolete. Nord

ne “Miller” part no. 9122230;

contains T874R1699 and Q674L1264. Y594R1763 Wirin

differences

(

old=new

)

W2=W, X=B, Z=F, K=X2,

W1=O.

R1490 209 Trol-A-Temp; contains T874R1707 and Q674L1678. None See Trol-A-Temp for

replacement.

R1508 209 Trol-A-Temp; contains T874R1715 and Q674L1686. None See Trol-A-Temp for

replacement.

R1516 132 Obsolete. Sn

der General part no. 654958B07;

contains T874R1723, Q674L1702 and C815A1005. Y594R1763 Wirin

differences

(

old=new

)

W1=W, C=B, X=X2.

R1524 108 Obsolete. Inter-Cit

Products part no.

HQ1147925HW; contains T874R1731 and

Q674L1132.

Y594R1292

R1532 108 Heil Quaker part no. 1060322; model no.

TAXB004TW01; contains T874R1749 and

Q674L1132.

Y594R1292

R1607 108 Obsolete. Keeprite THPC; contains T874R1814 and

Q674L1132. Y594R1292

Table 10. Y594 Cross Reference.

Model

Number Fig.

No. Description Trade Model

ReplacementaRemarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—894

R1615 230 TRADELINE; contains T874R1822 and

Q674L1710; replaces Y594R1326

(

T874R1491/

Q674L1553

)

Y594R1615

R1623 134 Obsolete. Rheem Universal Parts part no. 41-

20796-46; contains T874R1558 and Q674L1504. Y594R1300

R1631 134 Rheem part no. 41-20796-29; contains T874R1442

and Q674L1504. Y594R1300

R1649 134 Ruud part no. 41-20796-33; contains T874R1434

and Q674L1504. Y594R1300

R1656 134 Obsolete. WeatherKin

part no. 41-20796-64;

contains T874R1830 and Q674L1504. Y594R1300

R1664 120 TRADELINE; contains T874R1871 and

Q674L1736; direct replacement for York

2TH11702224

(

Y594R1011 contains T874R1046/

Q674L1272

)

Y594R1664

R1672 120 TRADELINE; contains T874R1889, Q674L1736

and C815A1054; direct replacement for York

2TH11702324

(

Y594R1151 contains T874R1251/

Q674L1272/C815A1039

)

and 6TH11702224

(

Y594R1193 contains T874R1327/Q674L1272

)

Y594R1672

R1680 230 TRADELINE; same as Y594R1615 except Premier

White® color; contains T874R1897 and

Q674L1751; direct replacement for Y594R1326

(

T874R1491/Q674L1553

)

Y594R1680

R1698 120 Obsolete. TRADELINE; Premier White® color;

contains T874R1905, Q674L1777 and C815A1054. Y594R1672 Replacement is bei

R1706 120 Obsolete. TRADELINE; same as Y594R1664

except Premier White® color; contains T874R1913

and Q674L1777; direct replacement for Y594R1011

(

T874R1046/Q674L1272

)

York part no.

2TH11702224.

Y594R1664 Replacement is bei

R1714 228 Obsolete. Lennox part no. 97E79; Canada; Premier

White® color; contains T874R1855 and

Q674L1728.

Y594R1763 Wirin

differences

(

old=new

)

Y1=Y, L=F, W1=W, E=W2,

C=B.

R1722 115 Obsolete. Econar; contains T874R1921 and

Q674L1207. Y594R1243a

R1748 197 American Standard

(

Trane

)

part no. ASYSTAT651A;

contains T874R1939 and Q674L1801. Y594R1763a

R1755 168 Obsolete. Inter-Cit

Products part no.

HQ1149376HW; contains T874R1947 and

Q674L1819.

Y594R1425a

R1763 197 TRADELINE: contains T874R1954 and

Q674L1827; direct replacement for Y594R1136

(

T874R1053/Q674L1140

)

, Y594R1748

(

T874R1939/Q674L1801

)

Trane part no.

ASYSTAT651A, Y594R1441

(

T874R1657/

Q674L1611

)

Trane part no. ASYSTAT651.

Y594R1763

R1771 115 Obsolete. Consolidated Industries part no.

9036100; contains T874R1962 and Q674L1843. Y594R1680aIncludes CHECK LED.

R1789 120 York Canada part no. 2TH11701524; contains

T874R1970 and Q674L1850. Y594R1672aReplacement has °F

scaleplate.

Table 10. Y594 Cross Reference.

Model

Number Fig.

No. Description Trade Model

ReplacementaRemarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

95 60-2485—8

R1797 125 TRADELINE; contains T874R1988 and

Q674L1868; direct replacement for Y594R1235

(

T874R1368/Q674L1421

)

Evcon/Coleman part no.

3600-368

)

Y594R1797a

R1805 245 Obsolete. Amana part no. 10636702; contains

T874R2002 and Q674L1876. Y594R1797 Wirin

differences

(

old=new

)

C/X=X.

R1813 245 Obsolete. Amana part no. 10636704; contains

T874R2010 and Q674L1884. Y594R1797 Wirin

differences

(

old=new

)

C/X=X, W3=W2.

R1821 125 Obsolete. York lo

o; part no. 2TH11703424A;

contains T874R2028 and Q674L1918. Y594R1797

R1839 134 Rudd lo

o; part no. 41-20796-48; contains

T874R2036 and Q674L1504. See OEM for

replacement.

R1854 123 Obsolete. Rheem lo

o; part no. 41-20796-47;

contains T874R1996 and Q674L1504. Y594R1300

Y594W

W1014 54 Contains T874W1015, Q674B1216 and

C815A1005. Y594W1014

W1022 140 Obsolete. Rheem part no. 41-20797-19; contains

T874W1031, Q674L1546 and C815A1005. T8611M2025.

W1030 68 Obsolete. Inter-Cit

Products part no. 1072350;

contains T874W1072, Q674L1835 and C815A1005

Outdoor Thermistor.

T8611M2025

(

pro

rammable

)

Includes ni

ht setback.

W1055 247 Obsolete. Addison lo

o; part no. 843-277; contains

T874W1106, Q674L1934 and C815A1005. T8611M2025

Y594Y

Y1004 210 Obsolete. Mammoth part no. 71117301; contains

T874Y1005 and Q674E1353. See OEM for

replacement.

Y1012 248 Obsolete. WaterFurnace lo

o; part no. TA21H03;

contains T874Y1013 and Q674F1675.

Table 10. Y594 Cross Reference.

Model

Number Fig.

No. Description Trade Model

ReplacementaRemarks

aBoth the thermostat and subbase must be replaced.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—896

WIRING DIAGRAMS

Fig. 44. Schematic and hookup of T874A,B,C,D,E,F with Q674B. Used in standard applications.

Fig. 45. Schematic and hookup of T874C,D with Q674B. Used in standard applications.

FALL

(HOT)

HEAT RELAY 2

HEAT RELAY 1

HEAT

OFF

COOL

SYSTEM

SWITCH

H1 ANTICIPATOR

C1 ANTICIPATOR

AUTO

FAN

SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

JUMPER RH, RC FOR SINGLE TRANSFORMER.

M2903

HEAT CHANGEOVER

VALVE

(HOT)

COOL CHANGEOVER

VALVE

FAN RELAY

COMPRESSOR

CONTACTOR 2

COMPRESSOR

CONTACTOR 1

FALL

C2 ANTICIPATOR

RISE

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H2 ANTICIPATOR

NOTE:

Model Heating Cool-

ing

No. Bulbs Bulbs

T874A H1 C1

T874B H1 C1,C2

T874C H1,H2 C1

T874D H1,H2 C1,C2

T874E C1,C2

T874D H1,H2

FALL

(HOT)

HEAT RELAY 2

HEAT RELAY 1

HEAT

OFF

COOL

SYSTEM

SWITCH

H1 ANTICIPATOR

C1 ANTICIPATOR

AUTO

FAN

SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

JUMPER RH, RC FOR SINGLE TRANSFORMER.

M933C

HEAT CHANGEOVER

VALVE

(HOT)

COOL CHANGEOVER

VALVE

FAN RELAY

COMPRESSOR

CONTACTOR 2

COMPRESSOR

CONTACTOR 1

FALL

C2 ANTICIPATOR

RISE

3OPTIONAL LED ON SOME MODELS.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H2 ANTICIPATOR

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

97 60-2485—8

Fig. 46. Schematic and hookup of T874A,B,D with Q674B. Used in standard applications.

Fig. 47. Schematic and hookup of T874R with Q674B. Used in heat pump applications.

FALL

HEAT RELAY 2

HEAT RELAY 1

HEAT

OFF

COOL

SYSTEM

SWITCH

H1 ANTICIPATOR

C1 ANTICIPATOR

AUTO

FAN

SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

M2904

HEAT CHANGEOVER

VALVE

COOL

CHANGEOVER

VALVE

FAN RELAY

COMPRESSOR

CONTACTOR 2

COMPRESSOR

CONTACTOR 1

FALL

C2 ANTICIPATOR

RISE

(HOT)

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H2 ANTICIPATOR

(HOT)

L2 1

COOL

HEAT

FALL

H1/C1

ANTICIPATOR

SYSTEM

SWITCH

FAN RELAY

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED. M2906

OFF

COOL CHANGEOVER

VALVE

FALL

FAN

SWITCH

AUTO

THERMOSTAT SUBBASE SYSTEM COMPONENTS

AUX. HT.

RELAY

COMPRESSOR

CONTACTOR

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—898

Fig. 48. Schematic and hookup of T874D with Q674B. Used in standard applications.

FALL

FAN RELAY

HEAT RELAY 1

HEAT

OFF

COOL

SYSTEM

SWITCH

H1 ANTICIPATOR

C1 ANTICIPATOR

AUTO

FAN

SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

CLOGGED FILTER, SERVICE SWITCH. M2905

THERMOSTAT SUBBASE SYSTEM COMPONENTS

HEAT CHANGEOVER

VALVE

(HOT)

COOL CHANGEOVER

VALVE

COMPRESSOR

CONTACTOR 2

COMPRESSOR

CONTACTOR 1

FALL

C2 ANTICIPATOR

RISE

C2 Y1

HEAT RELAY 2

EXTERNAL

FAN SWITCH

(HOT)

FILTER

LED (RED)

ANTICIPATOR

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

99 60-2485—8

Fig. 49. Schematic and hookup of T874C with Q674B. Used in standard applications.

Fig. 50. Schematic and hookup of T874G with Q674B. Used in heat pump applications.

(HOT)

FALL

RISE

(HOT)

L2 1

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

HEAT RELAY 1

BLOWER RELAY

HEAT RELAY 2

COMPRESSOR

CONTACTOR

HSII

CONTROL

PANEL

LO SPEED

LED (GREEN)

HI SPEED

LED (GREEN

COOL LED

(YELLOW)

HEAT

LED (RED)

FAN SWITCH

AUTO

SYSTEM

SWITCH

HEAT

OFF

COOL

C1 ANTICIPATOR

H2 ANTICIPATOR

ANTICIPATOR

M5945

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H1 FALL

FALL

RISE

C1 RISE

(HOT)

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

ANTICIPATOR

H2 ANTICIPATOR

C1 ANTICIPATOR

FAN

SWITCH

AUTO

SYSTEM

SWITCH

HEAT

OFF

COOL

AUX. HT. RELAY

FAN RELAY

COMPRESSOR

CONTRACTOR

COOL CHANGEOVER

VALVE

M8000

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8100

Fig. 51. Schematic and hookup of T874D with Q674B. Used in standard applications.

Fig. 52. Schematic and hookup of T874C with Q674B. Used in standard applications.

RISE

(HOT)

L2 1

(HOT)

RISE

FALL

M5944

H1 ANTICIPATOR

H2 ANTICIPATOR

C1 ANTICIPATOR

C2 ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

FIELD WIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER.

B, O TERMINALS ON SOME MODELS.

11 Y2

SYSTEM

SWITCH

HEAT

OFF

COOL

AUTO

FAN

SWITCH

HEAT RELAY 1

FAN RELAY

HEAT RELAY 2

HEAT CHANGEOVER VALVE

COOL CHANGEOVER VALVE

COMPRESSOR CONTACTOR 1

COMPRESSOR CONTACTOR 2

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FALL

C1 RISE

(HOT)

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

OPTIONAL FIELD WIRE JUMPER. W3 AND F TO BE JUMPERED EXCEPT FOR TWO STAGE GAS APPLICATION.

FIELD WIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H1 ANTICIPATOR

H2 ANTICIPATOR

C1 ANTICIPATOR

SYSTEM

SWITCH

HEAT

OFF

COOL

FAN SWITCH

AUTO

HEAT RELAY 1 FAN RELAY

HEAT RELAY 2

COMPRESSOR

CONTACTOR

M5999

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

101 60-2485—8

Fig. 53. Schematic and hookup of T874D with Q674B. Used in standard applications.

Fig. 54. Schematic and hookup of T874W with Q674B. Used in standard applications.

FALL

HEAT RELAY 2

HEAT RELAY 1

ANTICIPATOR

C1 ANTICIPATOR

AUTO

FAN SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED. M3202A

(HOT)

FAN RELAY

COMPRESSOR

CONTACTOR 2

COMPRESSOR

CONTACTOR 1

FALL

C2 ANTICIPATOR

RISE

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H2 ANTICIPATOR

SYSTEM

SWITCH

HEAT

OFF

COOL

L1 (HOT)

HEAT RELAY 3

FAN RELAY

HEAT CHANGEOVER VALVE

COMPRESSOR CONTACTOR 2

SYSTEM

SWITCH

HEAT

OFF

COOL

H1 ANTICIPATOR

FALL

1POWER SUPPLY. PROVIDE DISCONNECT

MEANS AND OVERLOAD PROTECTION

AS REQUIRED. M3674

AUTO

FAN SWITCH

FALL

COMPRESSOR CONTACTOR 1

HEAT RELAY 2

HEAT RELAY 1

C815A THERMISTOR

H2 ANTICIPATOR

FALL

H3 ANTICIPATOR

C2 ANTICIPATOR

RISE

COOL CHANGEOVER VALVE

C1 ANTICIPATOR

RESET HEATER

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8102

Fig. 55. Schematic and hookup of T874A,D,F with Q674D. Used in standard applications.

Fig. 56. Schematic and hookup of T874C with Q674B. Used in standard applications.

M3667A

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

JUMPER RC, RH FOR SINGLE TRANSFORMER.

B AND 5 TERMINALS AVAILABLE ON SOME MODELS.

COMPRESSOR

CONTACTOR 1

H2 ANTICIPATOR

C1 ANTICIPATOR

H1 ANTICIPATOR

HEAT RELAY 1

HEAT RELAY 2

COMPRESSOR

CONTACTOR 2

FALL L1

(HOT)

FALL H2

RISE

C2 ANTICIPATOR

RISE

FAN

SWITCH

SYSTEM

SWITCH

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FALL

(HOT)

L2 1

H2 FALL

C1 RISE

FAN

SWITCH

SYSTEM

SWITCH

AUTO

HEAT

OFF

COOL

COMPRESSOR

CONTACTOR 1

O RELAY

B RELAY

AUX. HT. RELAY

FAN RELAY

RESET

LED (RED)

C1 ANTICIPATOR

H2 ANTICIPATOR

H1 ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

11 Y1

SUBBASE SYSTEM COMPONENTS

M5975

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

103 60-2485—8

Fig. 57. Schematic and hookup of T874P with Q674B. Used in heat pump applications.

Fig. 58. Schematic and hookup of T874G with Q674D. Used in standard applications.

FALL

RISE

(HOT)

RISE

POWERSUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

JUMPER HONEYWELL SUPPLIED, FIELD INSTALLED.

C1 ANTICIPATOR

H1 ANTICIPATOR

FAN SWITCH

AUTO

SYSTEM

SWITCH

OVERRIDE

HEAT

OFF

COOL

10 T

COMPRESSOR

CONTACTOR FAN RELAY

CLOSED-DAY

OPEN-NITE B RELAY

JUMPER

COOL CHANGEOVER

VALVE

M8004

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H1 ANTICIPATOR

FALL

M3722

H2 ANTICIPATOR

FALL

ECONOMIZER

PACKAGE

RISE

C1 ANTICIPATOR

CONTROL

PANEL

THERMOSTAT SUBBASE SYSTEM COMPONENTS

NO FAN

SWITCH

NO SYSTEM

SWITCH

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8104

Fig. 59. Schematic and hookup of T874A with Q674Q. Used in fan coil applications.

Fig. 60. Schematic and hookup of T874C with Q674N. Used in evaporative cooler applications.

(HOT)

K2 RELAY

SYSTEM

SWITCH

HIGH

ANTICIPATOR

H1 FALL

1POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

M3729

HEAT

COOL

FAN

SWITCH

COMPRESSOR

CONTACTOR

MED G2

K1 RELAY

ANTICIPATOR

C1 RISE

HEAT

RELAY 1

OFF

HI LOMED

3 SPEED FAN

SCHEMATIC

LO L2 L1

THERMOSTAT SUBBASE SYSTEM COMPONENTS

(HOT) L2 1

H2 ANTICIPATOR

M2863

H1 ANTICIPATOR

C1 ANTICIPATOR

FALL

ELEC. HT. RELAY

FAN RELAY

COOL RELAY

CONTACT

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

AUTO

FAN

SWITCH

SYSTEM

SWITCH

EVAP

HEAT

OFF

COOL

CHANGEOVER

VALVE

COMPRESSOR

CONTACTOR

EVAPORATOR

RELAY

RISE

FALL

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

105 60-2485—8

Fig. 61. Schematic and hookup of T874C with Q674N. Used in evaporative cooler applications.

Fig. 62. Schematic and hookup of T874F with Q674B. Used in wood/coal applications.

(HOT)

EVAPORATOR

RELAY

ELEC. HT. RELAY

FAN RELAY

COMPRESSOR

CONTACTOR

CHANGEOVER

RELAY

ANTICIPATOR

AUTO

FAN

SWITCH

H1 ANTICIPATOR

RISE

FALL

SYSTEM

SWITCH

EVAP.

HEAT

COOL

OFF

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

ANTICIPATOR

M2862

THERMOSTAT SUBBASE SYSTEM COMPONENTS

(HOT)

FAN RELAY

SYSTEM

SWITCH

OFF

H2 ANTICIPATOR

FALL

1POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED. M3723A

AUTO

FAN SWITCH

COMPRESSOR

CONTACTOR

H1 ANTICIPATOR

AUX. HT. RELAY

HEAT

EXTERNAL COOLING

THERMOSTAT

(SUCH AS T87 F)

COOL

CWOOD/COAL

RELAY

FALL

YELLOW

GREEN

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8106

Fig. 63. Schematic and hookup of T874F with Q674D. Used in wood/coal applications.

Fig. 64. Schematic and hookup of T874A with Q674Q. Used in fan coil applications.

(HOT)

SYSTEM

SWITCH

H2 ANTICIPATOR

H2 FALL

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

M3725

NO FAN

SWITCH

H1 ANTICIPATOR

AUX. HT. RELAY

WOOD/COAL

RELAY

FALL

YELLOW

GREEN

THERMOSTAT SUBBASE SYSTEM COMPONENTS

HEAT/COOL

SWITCH

FALL

(HOT)

C1 RISE

M8005

ANTICIPATOR

1W1

Y1 HI

MED

K2 K2

COMPRESSOR CONTACTOR

O RELAY

K2 RELAY

K1 RELAY

B RELAY

HEAT RELAY 1

SYSTEM

SWITCHHEAT

OFF

COOL

FAN

SWITCH

MED

HIGH

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

SINGLE SETPOINT LEVER AND BIMETAL.

L2 L1

THERMOSTAT SUBBASE SYSTEM COMPONENT

3-SPEED FAN SCHEMATIC

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

107 60-2485—8

Fig. 65. Schematic and hookup of T874A with Q674B. Used in standard applications.

Fig. 66. Schematic and hookup of T874A,D,F with Q674D. Used in standard applications.

C1 RISE

(HOT)

L2 1

(HOT)

FALL

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M5976

ANTICIPATOR

H1 ANTICIPATOR

SYSTEM

SWITCH

HEAT

OFF

COOL

FAN

SWITCH

AUTO

NO. 1 HEAT RELAY

HEAT DAMPER

COOL DAMPER

FAN RELAY

NO. 1 COMP. RELAY

FILTER

LED (RED)

SERVICE LED

(YELLOW)

THERMOSTAT SUBBASE SYSTEM COMPONENTS

M7011

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H1 ANTICIPATOR

H2 ANTICIPATOR

H1 FALL

FALL

NO FAN

SWITCH

NO SYSTEM

SWITCH

(HOT)

L2 1

(HOT)

L2 1

HEAT RELAY 1

HEAT RELAY 2

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8108

Fig. 67. Schematic and hookup of T874R with Q674B. Used in heat pump applications.

Fig. 68. Schematic and hookup of T874P with Q674B. Used in heat pump applications.

M5998

FALL

(HOT)

L2 1

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H1/C1 ANTICIPATOR

FAN SWITCH

AUTO

SYSTEM

SWITCH

HEAT

OFF

COOL COMPRESSOR

CONTACTOR

AUX. HT. RELAY

HEAT CHANGEOVER

VALVE

FAN RELAY

FALL

RISE

CO L1

(HOT)

RISE

COMPRESSOR CONTACTOR

FAN RELAY

CLOSED-DAY

OPEN-NITE

B RELAY

SERVICE

LED (RED)

OVERRIDE

LED (RED)

FAN

SWITCH

AUTO

ANTICIPATOR

SYSTEM SWITCH

JUMPER

COOL CHANGEOVER VALVE

OVERRIDE

HEAT

OFF

C1 ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT

MEANS AND OVERLOAD PROTECTION

AS REQUIRED.

JUMPER HONEYWELL SUPPLIED, FIELD INSTALLED.

H2 MAKE OFFEST 8˚ F BELOW H1 MAKE.

3M101A

THERMOSTAT SUBBASE SYSTEM COMPONENTS

COOL

COMPRESSOR

FAULT

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

109 60-2485—8

Fig. 69. Schematic and hookup of T874V with Q674R. Used in fan coil applications.

Fig. 70. Schematic and hookup of T874C with Q674S. Used in heat pump applications.

RISE L1

(HOT)

L2 1

M107A

FAN SWITCH

AUTO HI

CONT.

SYSTEM SWITCH

OFF

COOL

C1 ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

COOL RELAY

FAN RELAY

Z RELAY

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H1 FALL

(HOT)

H2 FALL

FALL

NO FAN

SWITCH

SYSTEM

SWITCH

HEAT

COOL

THERMOSTAT SUBBASE SYSTEM COMPONENTS

SERVICE

LED (RED)

AUX. HT. RELAY

COMPRESSOR

CONTACTOR

M1402A

POWER SUPPLY. PROVIDE DISCONNECT

MEANS AND OVERLOAD PROTECTION AS REQUIRED.

COMPRESSOR

FAULT

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8110

Fig. 71. Schematic and hookup of T874A-D with Q674A. Used in standard applications.

Fig. 72. Schematic and hookup of T874D,E,F with Q674C. Used in standard applications.

FALL

(HOT)

HEAT RELAY 2

HEAT RELAY 1

HEAT

AUTO

COOL

SYSTEM

SWITCH

ANTICIPATOR

C1 ANTICIPATOR

AUTO

FAN SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

JUMPER RH, RC FOR SINGLE TRANSFORMER.

M932B

(HOT)

FAN RELAY

COMPRESSOR

CONTACTOR 2

COMPRESSOR

CONTACTOR 1

FALL

C2 ANTICIPATOR

RISE

3OPTIONAL LED ON SOME MODELS.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H2 ANTICIPATOR

CHECK

(HOT)

H2 ANTICIPATOR

H1 ANTICIPATOR

C1 ANTICIPATOR

C2 ANTICIPATOR

FALL

H1 W2

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

JUMPER TERMINALS RC-RH FOR SINGLE SYSTEM TRANSFORMER ONLY.

B,O TERMINALS ON SOME MODELS.

AUTO

FAN

SWITCH

SYSTEM

SWITCH

AUTO

OFF

RISE

FALL

RISE

HEAT DAMPER

COOL DAMPER

FAN RELAY

COMPRESSOR

CONTACTOR 2

COMPRESSOR

CONTACTOR 1

(HOT)

HEAT RELAY 1

HEAT RELAY 2

M5122A

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

111 60-2485—8

Fig. 73. Schematic and hookup of T874G with Q674C. Used in heat pump applications.

Fig. 74. Schematic and hookup of T874H with Q674C. Used in heat pump applications.

FALL

FAN RELAY

REVERSING

VALVE RELAY

OFF

AUTO

SYSTEM

SWITCH

H ANTICIPATOR

C ANTICIPATOR

AUTO

FAN SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M7008

THERMOSTAT SUBBASE SYSTEM COMPONENTS

OPEN-NIGHT

CLOSED-DAY

SETBACK

FALL

RISE

CO L1

(HOT)

COMPRESSOR

CONTACTOR

SETBACK

RELAY

RISE

(HOT)

L2 1

FAN RELAY

SYSTEM

SWITCH

OFF

AUTO

ANTICIPATOR

FALL

1POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

SERVICE LED ON SELECT MODELS. M3680A

AUTO

FAN SWITCH

COMPRESSOR

CONTACTOR

COOL CHANGEOVER

VALVE

RISE

ANTICIPATOR

THERMOSTAT SUBBASE SYSTEM COMPONENTS

SERVICE LED

(YELLOW)

COMPRESSOR

FAULT

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8112

Fig. 75. Schematic and hookup of T874A with Q674C. Used in standard applications.

Fig. 76. Schematic and hookup of T874A-D with Q674C. Used in standard applications.

RISE

(HOT)

H1 FALL

THERMOSTAT SUBBASE SYSTEM COMPONENTS

SYSTEM SWITCH

OFF

AUTO

FAN SWITCH

AUTO

HEAT RELAY

FILTER LED

(YELLOW)

SERVICE

LED (RED) FAN RELAY

ANTICIPATOR

THERMISTOR

ANTICIPATOR

EXTERNAL

TEMP.

READOUT

COMPRESSOR CONTACTOR

MOMENTARY

CIRCUIT

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE.

FILTER LED ON SELECT MODELS.

3M5731

M7025

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H1 ANTICIPATOR

H2 ANTICIPATOR

RISE

H1 FALL

FALL

RISE

C2 ANTICIPATOR

C1 ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

FOR T874C, DELETE C2.

AUTO

FAN

SWITCH

SYSTEM

SWITCH

OFF

HEAT CHANGEOVER

VALVE

HEAT RELAY 1

COMPRESSOR

CONTACTOR 1

HEAT RELAY 2

(HOT)

L2 1

COMPRESSOR

CONTACTOR 2

AUTO

FILTER

LED (YEL)

SERVICE

LED (RED)

(HOT)

COOL CHANGEOVER

VALVE

FAN RELAY

FILTER LED ON SELECT MODELS.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

113 60-2485—8

Fig. 77. Schematic and hookup of T874K with Q674C. Used in heat pump applications.

Fig. 78. Schematic and hookup of T874P with Q674C. Used in heat pump applications.

RISE

FALL

(HOT)

L2 1

(HOT)

L2 1

POWER SUPPLY. PROVIDE DISCONNECT

MEANS AND OVERLOAD PROTECTION

AS REQUIRED.

JUMPER RH AND RC FOR SINGLE

TRANSFORMER SYSTEM.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H1 ANTICIPATOR

ANTICIPATOR

SYSTEM

SWITCH

FAN

SWITCH

AUTO

OFF

AUTO

FAN RELAY

HEAT CHANGEOVER

VALVE

COMPRESSOR

CONTACTOR

M4729

RESET

LED (RED)

"O" RELAY

"B" RELAY

HEAT RELAY 1

HEAT RELAY 2

THERMOSTAT SUBBASE SYSTEM COMPONENTS

ANTICIPATOR

RISE

H2 FALL

ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

JUMPER HONEYWELL SUPPLIED, FIELD INSTALLED.

AUTO

FAN

SWITCH

SYSTEM

SWITCH

OFF

COMPRESSOR

CONTACTOR

AUTO

(HOT)

FAN RELAY

SETBACK

CONTACT

M7026

HEAT

CHANGEOVER

VALVE

REVERSING

VALVE

JUMPER

RISE

OVERRIDE

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8114

Fig. 79. Schematic and hookup of T874G,H with Q674C. Used in standard applications.

Fig. 80. Schematic and hookup of T874D with Q674E. Used in standard applications.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H1 ANTICIPATOR

RISE

H1 FALL

FALL

ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

SETBACK CONTACT ON Q674C1124.

AUTO

FAN

SWITCH

SYSTEM

SWITCH

OFF COMPRESSOR

CONTACTOR

AUTO

(HOT)

COOL

CHANGEOVER

VALVE

RESET

FAN RELAY

SETBACK

CONTACT

RISE

RESET

LED (RED)

H2 ON T874G. M7027

FALL

(HOT)

L2 1

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

OPTIONAL FIELDWIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

M5997

HEAT

RELAY 1 CONTACTOR

COMPRESSOR 1

FAN RELAY

HEAT RELAY 2

COMPRESSOR

FAULT COMPRESSOR

CONTACTOR 2

SERVICE

LED (RED)

SYSTEM

SWITCH OFF

HEAT

AUTO

COOL

C2 ANTICIPATOR

C1 ANTICIPATOR

RISE

H2 ANTICIPATOR

H1 ANTICIPATOR

11 Y2

FAN SWITCH

AUTO

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

115 60-2485—8

Fig. 81. Schematic and hookup of T874C with Q674C. Used in heat pump applications.

Fig. 82. Schematic and hookup of T874A,C,D with Q674E. Used in standard applications.

FALL

(HOT)

H2 ANTICIPATOR

OFF

AUTO

FAN

SWITCH

CHANGEOVER

RELAY

M5981

POWER SUPPLY. PROVIDE DISCONECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

SYSTEM COMPONENTSSUBBASETHERMOSTAT

FALL

C1 RISE

C1 ANTICIPATOR

AUTO

FAN

RELAY

COMPRESSOR

CONTACTOR

SYSTEM

SWITCH

FALL

RISE

(HOT)

L2 1

POWER SUPPLY. PROVIDE DISCONNECT

MEANS AND OVERLOAD PROTECTION

AS REQUIRED.

JUMPER RC, RH FOR SINGLE TRANSFORMER.

O AND B TERMINALS ON SELECTED MODELS.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H1 ANTICIPATOR

H2 ANTICIPATOR

C2 ANTICIPATOR

ANTICIPATOR

SYSTEM

SWITCH

FAN

SWITCH

AUTO

OFF

HEAT

AUTO

COOL

HEAT RELAY 2

HEAT RELAY 1

COMPRESSOR

CONTACTOR 1

COMPRESSOR

CONTACTOR 2

FAN RELAY

M934

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8116

Fig. 83. Schematic and hookup of T874G with Q674C. Used in standard applications.

Fig. 84. Schematic and hookup of T874G with Q674E. Used in heat pump applications.

FAN

SWITCH

AUTO

CHECK LED

(RED)

M5982

POWER SUPPLY. PROVIDE DISCONECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

H2 ANTICIPATOR

FALL

RISE

C1 ANTICIPATOR

RISE

FALL

H1 ANTICIPATOR

SYSTEM COMPONENTSSUBBASE

THERMOSTAT

(HOT)

L2 1

COMPRESSOR

CONTACTOR 1

C2 ANTICIPATOR

AUTO

COOL

HEAT

OFF

HEAT RELAY 1

FAN RELAY

HEAT RELAY 2

COMPRESSOR

CONTACTOR 2

H1 FALL

H2 FALL

RISE

(HOT)

L2 1

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H1 ANTICIPATOR

H2 ANTICIPATOR

C1 ANTICIPATOR

SYSTEM

SWITCH

FAN

SWITCH

AUTO

OFF

HEAT

AUTO

COOL

AUX. HT.

RELAY

DEFROST

RELAY

DEFROST

RELAY

FAN RELAY

HIGH PRESSURE

SWITCH

DEFROST

SWITCH

COOL

CHANGEOVER

VALVE OUTDOOR

FAN RELAY

COMPRESSOR

CONTACTOR

DEFROST

RELAY

M4666

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

117 60-2485—8

Fig. 85. Schematic and hookup of T874A-D with Q674E. Used in standard applications.

Fig. 86. Schematic and hookup of T874G with Q674E. Used in heat pump applications.

FALL

ANTICIPATOR

HEAT RELAY 2

(HOT)

L2 1

COMPRESSOR

CONTACTOR 1

M5983

POWER SUPPLY. PROVIDE DISCONECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

SYSTEM COMPONENTSSUBBASETHERMOSTAT

FAN RELAY

RISE

OFF

SYSTEM

SWITCH

FAN

SWITCH

HEAT

AUTO

COOL

AUTO

FALL

H2 ANTICIPATOR

ANTICIPATOR

C2 ANTICIPATOR

HEAT RELAY 1

COMPRESSOR

CONTACTOR 2

FALL

H2 FALL

RISE

C1 RISE

(HOT)

L2 1

(HOT)

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H1 ANTICIPATOR

H2 ANTICIPATOR

C1 ANTICIPATOR

SYSTEM

SWITCH

FAN

SWITCH

AUTO

OFF

HEAT

AUTO

COOL

AUX. HT. RELAY

DEFROST RELAY

CONTACT

COOL

CHANGEOVER

VALVE

COMPRESSOR

CONTACTOR

DEFROST

RELAY

M4667

HIGH

PRESSURE

SWITCH

DEFROST RELAY

CONTACT

FAN RELAY

DEFROST

SWITCH

D. F. O.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8118

Fig. 87. Schematic and hookup of T874D with Q674E. Used in standard applications.

Fig. 88. Schematic and hookup of T874B,D with Q674E. Used in standard applications.

RISE

FALL

H1 FALL

(HOT)

L2 1

(HOT)

L2 1

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

FIELDWIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER.

H1 ANTICIPATOR

H2 ANTICIPATOR

C1 ANTICIPATOR

C2 ANTICIPATOR

SYSTEM

SWITCH

FAN

SWITCH

AUTO

OFF

HEAT

AUTO

COOL

COMPRESSOR

CONTACTOR 1

COMPRESSOR

CONTACTOR 2

M4668

SYSTEM

FAULT CONTACT

FAN RELAY

HEAT RELAY 1

HEAT RELAY 2

LOCKOUT LED

(RED)

THERMOSTAT SUBBASE SYSTEM COMPONENTS

RISE

FALL

H1 FALL

(HOT)

L2 1

1POWER SUPPLY. PROVIDE DISCONNECT

MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

ANTICIPATOR

H2 ANTICIPATOR

C1 ANTICIPATOR

C2 ANTICIPATOR

SYSTEM

SWITCH

FAN

SWITCH

AUTO

OFF

HEAT

AUTO

COOL

COMPRESSOR

CONTACTOR 1

COMPRESSOR

CONTACTOR 2

M4669

FAN RELAY

HEAT RELAY 1

HEAT RELAY 2

HIGH LED (RED)

LOW LED (GREEN)

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

119 60-2485—8

Fig. 89. Schematic and hookup of T874D with Q674E. Used in standard applications.

Fig. 90. Schematic and hookup of T874D with Q674G. Used in standard applications.

1M7023

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H1 ANTICIPATOR

H2 ANTICIPATOR

RISE

H1 FALL

FALL

C2 RISE C2 ANTICIPATOR

C1 ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

AUTO

FAN

SWITCH

SYSTEM

SWITCH

HEAT

OFF

COOL

HEAT CHANGEOVER

VALVE

HEAT

RELAY 1

COMPRESSOR

CONTACTOR 1

FAN RELAY

HEAT RELAY 2

(HOT)

L2 1

(HOT)

L2 1

COOL CHANGEOVER

VALVE

COMPRESSOR

CONTACTOR 2

AUTO

FILTER

LED (YEL)

SERVICE

LED (RED)

OFF

AUTO

SYSTEM

SWITCH

1M7022

THERMOSTAT SUBBASE SYSTEM COMPONENTS

(HOT)

L2 1

H1 ANTICIPATOR

H2 ANTICIPATOR

C1 RISE

H1 FALL

FALL

C2 RISE C2 ANTICIPATOR

C1 ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

NO FAN

SWITCH

HEAT RELAY 1

HEAT RELAY 2

T RELAY

HEAT

CHANGEOVER

VALVE

COMPRESSOR

CONTACTOR 2

COMPRESSOR

CONTACTOR 1

(HOT)

L2 1

FILTER LED (YEL)

SERVICE

LED (RED)

FILTER

LED (YEL)

SERVICE

LED (RED)

COOL

CHANGEOVER

VALVE

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8120

Fig. 91. Schematic and hookup of T874A-F,Q with Q674G. Used in standard applications.

Fig. 92. Schematic and hookup of T874C with Q674G. Used in heat pump applications.

FALL

(HOT)

HEAT RELAY 2

HEAT RELAY 1

OFF

AUTO

SYSTEM

SWITCH

ANTICIPATOR

C1 ANTICIPATOR

NO FAN

SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

JUMPER RH, RC FOR SINGLE TRANSFORMER.

M3201B

(HOT)

COOL DAMPER

HEAT DAMPER

COMPRESSOR

CONTACTOR 2

COMPRESSOR

CONTACTOR 1

FALL

C2 ANTICIPATOR

RISE

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H2 ANTICIPATOR

OFF

H1 ANTICIPATOR

H2 ANTICIPATOR

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED. M6008A

C1 ANTICIPATOR

AUTO

FALL

CHANGEOVER

RELAY

(HOT)

FAN RELAY

COMPRESSOR

CONTACTOR

THERMOSTAT SUBBASE SYSTEM COMPONENTS

NO FAN

SWITCH

SYSTEM

SWITCH

RISE

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

121 60-2485—8

Fig. 93. Schematic and hookup of T874D with Q674K. Used in standard applications.

Fig. 94. Schematic and hookup of T874D with Q674G. Used in standard applications.

H1 FALL

H2 FALL

RISE

(HOT)

L2 1

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

NO FAN

SWITCH

SYSTEM

SWITCH

OFF

HEAT

AUTO

COOL

C2 ANTICIPATOR

C1 ANTICIPATOR

ANTICIPATOR

H1 ANTICIPATOR

HEAT FAN RELAY

HEAT RELAY

COMPRESSOR

CONTACTOR 1

COMPRESSOR

CONTACTOR 2

M4664

HEAT CHANGEOVER

VALVE

OFF

AUTO

SYSTEM

SWITCH

1M7013

THERMOSTAT SUBBASE SYSTEM COMPONENTS

(HOT)

L2 1

HEAT

RELAY 2

COMPRESSOR

CONTACTOR 1

COMPRESSOR

CONTACTOR 2

(HOT)

L2 1

H1 ANTICIPATOR

H2 ANTICIPATOR

RISE

H1 FALL

FALL

C2 RISE C2 ANTICIPATOR

C1 ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

NO FAN

SWITCH

HEAT

RELAY 1

COOL CHANGEOVER

VALVE

"T" RELAY

FILTER

LED (YELLOW)

SERVICE

LED (RED)

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8122

Fig. 95. Schematic and hookup of T874F with Q674K. Used in wood/oil applications.

Fig. 96. Schematic and hookup of T874C with Q674C. Used in standard applications.

FALL

OFF

WOOD

SYSTEM

SWITCH

H1 ANTICIPATOR

WOOD/OIL

OIL

OIL LED

(RED)

M5984

POWER SUPPLY. PROVIDE DISCONECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

SYSTEM COMPONENTSSUBBASETHERMOSTATS

FALL

NO FAN

SWITCH

OIL RELAY

WOOD RELAY

(HOT)

L2 1

WOOD LED

(GREEN)

H2 ANTICIPATOR

FALL

(HOT)

POWER SUPPLY. PROVIDE DISCONNECT

MEANS AND OVERLOAD PROTECTION AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

(HOT)

RISE

H1 FALL

FAN SWITCH

AUTO

SYSTEM

SWITCH

OFF

AUTO

C1 ANTICIPATOR

H2 ANTICIPATOR

NO. 1 HEAT RELAY

NO. 2

HEAT RELAY

HEAT

DAMPER

COOL DAMPER

FAN RELAY

NO. 1 COMPRESSOR

CONTACTOR

ON LED

(YELLOW)

SERVICE

LED (RED)

M104A

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

123 60-2485—8

Fig. 97. Schematic and hookup of T874P with Q674C. Used in heat pump applications.

Fig. 98. Schematic and hookup of T874D with Q674E. Used in standard applications.

FALL

RISE

(HOT)

RISE

COMPRESSOR CONTACTOR

FAN RELAY

CLOSED-DAY

OPEN-NITE

B RELAY

SERVICE

LED (RED)

OVERRIDE

LED (RED)

FAN

SWITCH

AUTO

ANTICIPATOR

SYSTEM SWITCH

JUMPER

COOL CHANGEOVER VALVE

OVERRIDE

AUTO

OFF

C1 ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

JUMPER HONEYWELL SUPPLIED, FIELD INSTALLED.

H2 MAKE OFFEST 8˚ F BELOW H1 MAKE.

3M100A

THERMOSTAT SUBBASE SYSTEM COMPONENTS

COMPRESSURE FAILURE

M5106A

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H1 ANTICIPATOR

H2 ANTICIPATOR

RISE

H1 FALL

FALL

RISE

C2 ANTICIPATOR

C1 ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

T874A IS SINGLE-STAGE (NO W2 OR Y2).

AUTO

FAN

SWITCH

SYSTEM

SWITCH

OFF

CHANGEOVER

RELAY

HEAT RELAY 1

COMPRESSOR

CONTACTOR 1

HEAT RELAY 2

(HOT)

L2 1

COMPRESSOR

CONTACTOR 2

AUTO

HEAT

SERVICE

LED (RED)

(HOT)

CHANGEOVER

RELAY

FAN RELAY

SYSTEM MONITOR

COOL

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8124

Fig. 99. Schematic and hookup of T874C with Q674C. Used in standard applications.

H1 ANTICIPATOR

H2 ANTICIPATOR

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED.

MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE.

H1 AND C1 ARE DPST SWITCHES.

M531

C1 ANTICIPATOR

AUTO

FALL

HEAT RELAY 1

HEAT RELAY 2

COMPRESSOR RELAY

(HOT)

RFAN RELAY

AUTO

OFF

SERVICE

LED (RED)

MOMENTARY

CIRCUIT

TEXTERNAL

TEMP.

READOUT

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FAN

SWITCH

SYSTEM

SWITCH

RISE

THERMISTER

H3 OFFSET 12°F FROM H2 FOR NIGHT SETBACK.

THERMISTOR INTERNAL TO THERMOSTAT.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

125 60-2485—8

Fig. 100. Schematic and hookup of T874W with Q674C. Used in standard applications.

Fig. 101. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

H1 ANTICIPATOR

H2 ANTICIPATOR

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED.

MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE.

H1 AND C1 ARE DPST SWITCHES.

M532

ANTICIPATOR

C2 ANTICIPATOR

AUTO

FALL

HEAT RELAY 1

HEAT RELAY 2

HEAT RELAY 3

COMPRESSOR RELAY

(HOT)

RFAN RELAY

AUTO

OFF

SERVICE

LED (RED)

MOMENTARY

CIRCUIT

TEXTERNAL

TEMP.

READOUT

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FAN

SWITCH

SYSTEM

SWITCH

RISE

THERMISTER

COMPRESSOR

CONTACTOR 2

H3 OFFSET 12°F FROM H2 FOR NIGHT SETBACK.

THERMISTOR INTERNAL TO THERMOSTAT.

(HOT)

COOL CHANGEOVER

VALVE

SYSTEM

SWITCH

OFF

HEAT

H1/C1

ANTICIPATOR

FALL

1POWER SUPPLY. PROVIDE

DISCONNECT MEANS AND

OVERLOAD PROTECTION

AS REQUIRED.

M3718A

AUTO

FAN SWITCH R

COMPRESSOR

CONTACTOR

EM. HT.

LED (RED)

AUX. HT. RELAY

EM. HT.

ANTICIPATOR

FALL

COOL

FAN RELAY

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8126

Fig. 102. Schematic and hookup of T874J,R with Q674L. Used in heat pump applications.

H2 FALL

FALL

(HOT)

L2 1L1

(HOT)

L2 1

POWER SUPPLY. PROVIDE DISCONNECT

MEANS AND OVERLOAD PROTECTION

AS REQUIRED.

FIELD WIRE JUMPER TO ALLOW SINGLE

SYSTEM TRANSFORMER.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H1/C1

ANTICIPATOR

H2 ANTICIPATOR

SYSTEM

SWITCH

FAN

SWITCH

AUTO

OFF

HEAT

EM. HT.

COOL

INTERNAL

THERMOSTAT

OVERLOAD

SWITCH

SUPPL. ELEC.

HT. RELAY

COOL CHANGEOVER

VALVE

COMPRESSOR

CONTACTOR

M4726

EM. HT.

LED (RED)

EM. HT. RELAY

TIME DELAY

FAN RELAY

OUTDOOR

THERMOSTAT

EM. HT.

RELAY CONTACT

FAN RELAY

HIGH

PRESSURE

SWITCH

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

127 60-2485—8

Fig. 103. Schematic and hookup of T874G with Q674L. Used in heat pump applications.

Fig. 104. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

H2 ANTICIPATOR

SUPL. HT.

LED (RED)

M4665

POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

SYSTEM COMPONENTSSUBBASETHERMOSTAT

(HOT)

H1 FALL

H2 FALL

CO RISE

C1 RISE

H1 ANTICIPATOR

C1 ANTICIPATOR

SYSTEM

SWITCH

SUPL. HT.

COOL

OFF

FAN

SWITCH

AUTO

ON FAN RELAY

COOL CHANGEOVER VALVE

OUTDOOR

THERMOSTAT

HEAT RELAY 1

HEAT RELAY

CONTACT 1 HEAT RELAY 2

HEAT RELAY

CONTACT 2 HEAT RELAY 3

COMPRESSOR

CONTACTOR 1

N.O. SWITCH – INSTALLER ADDED, TO LIGHT SUPL. HT. LED

WHEN COMPRESSOR OPERATION IS NOT NORMAL.

COMPRESSOR

FAULT

HEAT

(HOT)

POWER SUPPLY. PROVIDE DISCONNECT

MEANS AND OVERLOAD PROTECTION

AS REQUIRED.

OPTIONAL FIELD WIRE JUMPER TO CYCLE

AUXILIARY HEAT RELAY H1 INSTEAD OF

H2 (FASTER RESPONSE).

THERMOSTAT SUBBASE SYSTEM COMPONENTS

M4728

FAN

SWITCH

AUTO

EM. HT. LED

(RED)

FALL

H2 ANTICIPATOR

COM

R8233B

SYSTEM

SWITCH

OFF

HEAT

EM. HT.

COOL

FALL

EM. HT. RELAY

AUX. HT. RELAY

"B" RELAY

COMPRESSOR

CONTACTOR

ELEC. HT.

RELAY

H1/C1

ANTICIPATOR

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8128

Fig. 105. Schematic and hookup of T874C with Q674L. Used in heat pump applications.

Fig. 106. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

OFF

COOL

IHRI

RHI

FAN SWITCH

SYSTEM

SWITCH

SYSTEM

MONITOR

SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

M8384

EM. HT. RELAY

EM. HT. LED

(RED)

EM. HT.

HEAT

FAN RELAY

HEAT RELAY 2

HEAT RELAY 1

AUTO

H1 FALL

H2 ANTICIPATOR

H1 ANTICIPATOR

C1 ANTICIPATOR

FALL

RISE

COMPRESSOR

CONTRACTOR

(HOT)

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FALL

(HOT)

L2 1

1POWER SUPPLY. PROVIDE DISCONNECT

MEANS AND OVERLOAD PROTECTION

AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H1/C1

ANTICIPATOR

H2 ANTICIPATOR

SYSTEM

SWITCH

FAN SWITCH

AUTO

OFF

HEAT

EM. HT.

COOL

AUX. HT. RELAY

EM. HT. RELAY

COOL CHANGEOVER

VALVE

COMPRESSOR

CONTACTOR

FAN RELAY

M4724

EM. HT.

LED

(RED)

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

129 60-2485—8

Fig. 107. Schematic and hookup of T874D with Q674L. Used in heat pump applications.

Fig. 108. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

C2 RISE

RISE

H2 FALL

FALL

(HOT)

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

ANTICIPATOR

C2 ANTICIPATOR

ANTICIPATOR

C1 ANTICIPATOR

SYSTEM

SWITCH

FAN

SWITCH

AUTO

OFF

HEAT

EM. HT.

COOL

M4727

EM. HT.

LED (RED)

COMPRESSOR

CONTACTOR 1

COMP.

FAILURE

EM. HT.

RELAY CONTACT

EM. HT. RELAY

COMPRESSOR

CONTACTOR 2

OUTDOOR

THERMSTAT SUPPL. HT.

RELAY

FAN RELAY

COOL CHANGEOVER

VALVE

FALL

(HOT)

L2 1

1POWER SUPPLY. PROVIDE DISCONNECT

MEANS AND OVERLOAD PROTECTION

AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H1/C1

ANTICIPATOR

FAN

SWITCH

AUTO

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

AUX. HT. RELAY

FAN RELAY

COOL CHANGEOVER

VALVE

COMPRESSOR

CONTACTOR

M4725

AUX. HT.

LED (YELLOW)

EM. HT.

LED (RED)

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8130

Fig. 109. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

FALL

(HOT)

L2 1

1POWER SUPPLY. PROVIDE DISCONNECT

MEANS AND OVERLOAD PROTECTION

AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FALL

C1 H1/ C1

ANTICIPATOR

SYSTEM

SWITCH

FAN

SWITCH

AUTO

OFF

HEAT

EM. HT.

COOL

AUX. HT. RELAY

FAN RELAY

AUX. HT.

LED (GREEN)

COOL

CHANGEOVER

VALVE

COMPRESSOR

FAILURE

EM. HT.

LED (RED)

OUTDOOR

THERMOSTAT

OUTDOOR

THERMISTOR

COMPRESSOR

CONTACTOR

RESET

HEATER

M5071

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

131 60-2485—8

Fig. 110. Schematic and hookup of T87C,R with Q674L. Used in heat pump applications.

(HOT)

EM. HT.

LED (YELLOW)

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

ANTICIPATOR

1POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

M2854

FALL

AUTO

FAN SWITCH

OUTDOOR

THERMOSTAT SUPL. ELEC.

HT. RELAY

COMPRESSOR

CONTACTOR

OVERLOAD

SWITCH

INTERNAL

THERMOSTAT

HI PRESSURE

SWITCH

FAN

RELAY

EM. HT. RELAY

CONTACT TIME DELAY

FAN RELAY

ELEC. HT. RELAY

FALL

ANTICIPATOR

RISE

ANTICIPATOR

REMOVE FACTORY INSTALLED V-VR JUMPER WHEN

CONNECTING A TWO TRANSFORMER SYSTEM.

SERVICE

C815A OUTDOOR

THERMISTOR

COOL CHANGEOVER

VALVE

SERVICE

LED (RED)

RESET

REMOVE FACTORY-INSTALLED S-Y JUMPER TO DISABLE SERVICE LIGHT.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8132

Fig. 111. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

(HOT)

COOL

HEAT

FALL

SYSTEM

SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED. M2851

OFF

H1 C1

2REMOVE FACTORY INSTALLED V-VR JUMPER WHEN

CONNECTING A TWO TRANSFORMER SYSTEM.

COMPRESSOR

CONTACTOR

OVERLOAD

SWITCH

INTERNAL

THERMOSTAT

HIGH

PRESSURE

SWITCH

FAN RELAY SERVICE

OUTDOOR

THERMOSTAT

EM. HT.

RELAY

SUPPL. ELEC.

HT. RELAY

EM. HT.

RELAY EM. HT.

RELAY

C815A

OUTDOOR

THERMISTOR

COOL CHANGEOVER

VALVE

EM. HT. LED

(YELLOW)

SERVICE

LED (RED)

EM. HT.

AUTO

FAN

SWITCH

RESET

HEATER

H1/ C1

ANTICIPATOR

FALL

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

133 60-2485—8

Fig. 112. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

OFF

COOL

COMPRESSOR

FAILURE

FAN

SWITCH

SYSTEM

SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT

MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

M8383

AUX. HT. RELAY

EM. HT. LED

(RED)

AUX. HT. LED

(GREEN)

EM. HT.

HEAT

COOL CHANGEOVER

VALVE

FAN RELAY

EM. HT. RELAY

AUTO

FALL

H1/C1

ANTICIPATOR

H2 FALL

COMPRESSOR

CONTACTOR

(HOT)

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8134

Fig. 113. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

FALL

(HOT)

L2 1

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H1/C1

ANTICIPATOR

FALL

H2 ANTICIPATOR

SYSTEM

SWITCH

FAN

SWITCH

AUTO

OFF

HEAT

EM. HT.

LED (RED)

EM. HT.

COOL

EM. HT. RELAY

DEFROST RELAY

DEFROST

RELAY

FAN RELAY

M4720

COMPRESSOR

CONTACTOR

HIGH

PRESSURE

SWITCH

COOL CHANGEOVER

VALVE

LOW AMBIENT

CUTOFF

CHECK LED

(GREEN)

OPTIONAL COMP.

FAILURE DEVICE

HEAT

CONTRACTOR 3

HEAT

CONTRACTOR 2

OUTDOOR

THERMOSTAT

HEAT

CONTRACTOR 1

HIGH LIMIT

SWITCH

REVERSING

VALVE

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

135 60-2485—8

Fig. 114. Schematic and hookup of T874D with Q674L. Used in heat pump applications.

(HOT)

L2 1

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

ANTICIPATOR

1POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

FALL

AUTO

FAN SWITCH

FAN

RELAY

FALL

H2 ANTICIPATOR

RISE

ANTICIPATOR

REMOVE FACTORY INSTALLED V-VR JUMPER WHEN CONNECTING

A TWO TRANSFORMER SYSTEM.

OUTDOOR

THERMOSTAT HIGH SPEED

COMPRESSOR

CONTACTOR

LOW SPEED

COMPRESSOR

CONTACTOR

COOL

CHANGEOVER

VALVE

OUTDOOR

THERMOSTAT

SUPPL. ELEC.

HT. RELAY

SUPPL. ELEC.

HT. RELAY

EM. HT.

RELAY

C815A OUTDOOR

THERMISTOR

M2853

EM. HT. LED

(YELLOW)

EM. HT.

RELAY

SERVICE

LED (RED)

RESET

HEATER

ANTICIPATOR

SERVICE

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8136

Fig. 115. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

M5072A

(HOT) L1 L2

LACO CHP

RODT 1

RTD 1 EHR 1 RTD 2

ODT 2

EHR 2 RTD 3

SYSTEM

MONITOR

FAN RELAY

COMPRESSOR

CONTACTOR

COOL CHANGEOVER

VALVE

EM. HT.

RELAY

RTD 1

AUX. HT.

LED

(GREEN)

EM. HT.

LED (RED)

FAN SWITCH

AUTO

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

FALL

H1/C1

ANTICIPATOR

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

AUXILIARY HEAT LED AVAILABLE ON SOME MODELS.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

137 60-2485—8

Fig. 116. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

FALL

COM

OEH

(HOT)

COMPRESSOR

CONTACTOR

AUX. HT. RELAY

EM. HT. RELAY

EM. HT.

LED (RED)

EM. HT.

HEAT

OFF

COOL

COMP. FAULT

LED (YELLOW)

SYSTEM

SWITCH

FAN

SWITCH

AUTO

1 POWER SUPPLY. PROVIDE DISCONNECT

MEANS AND OVERLOAD PROTECTION

AS REQUIRED.

OPTIONAL FIELD WIRE JUMPER TO CYCLE

AUXILIARY HEAT RELAY WITH H1 INSTEAD

OF H2 (FASTER RESPONSE).

2ELEC.

HT. RELAY

M2857

H1/C1

ANTICIPATOR

H2 ANTICIPATOR

R8233B

THERMOSTAT SYSTEM COMPONENTS

SUBBASE

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8138

Fig. 117. Schematic and hookup of T874D with Q674L. Used in heat pump applications.

FALL

(HOT)

ENTHALPY

CONTROL RELAY

HEAT RELAY

CONTACT 1

DEFROST

RELAY

H1 ANTICIPATOR

H2 ANTICIPATOR

C1 ANTICIPATOR

C2 ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

OPTIONAL ECONOMIZER HOOKUP (DOTTED LINES).

M7755

FALL

RISE

THERMOSTAT SUBBASE SYSTEM COMPONENTS

MOTOR

OUTDOOR

FAN RELAY 1

DEFROST SWITCH

RELAY

TM1 TM2

OUTDOOR

FAN RELAY 2

DEFROST

SWITCH

LOW AMBIENT

THERMOSTAT 1

OUTDOOR

FAN RELAY 3

1ST STAGE

SHORT

CYCLE

CONTROL

2ND STAGE

SHORT

CYCLE

CONTROL

1ST STAGE LOW

PRESSURE LIMIT

2ND STAGE LOW

PRESSURE LIMIT

TIME DELAY

HEATER

ECONOMIZER

RELAY

ENTHALPY

CONTROL

ENTHALPY

CONTROL

RELAY 2

ENTHALPY

CONTROL

RELAY 1

TIME DELAY

DEFROST

RELAY

HEAT

RELAY 1

OUTDOOR

THERMOSTAT

SERVICE

DEFROST

RELAY

COOL CHANGEOVER

VALVE

SYSTEM

SWITCH

OFF

COOL

HEAT

EM. HT. LED

(GREEN)

SERVICE

LED (RED)

FAN

SWITCH

AUTO

MOTOR

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

139 60-2485—8

Fig. 118. Schematic and hookup of T874W with Q674L. Used in heat pump applications.

FALL

(HOT)

ECONOMIZER

RELAY

HEAT RELAY

CONTACT 1

DEFROST

RELAY

H2 ANTICIPATOR

ANTICIPATOR

C2 ANTICIPATOR

C1 ANTICIPATOR

RESET HEATER

POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

OPTIONAL ECONOMIZER HOOKUP (DOTTED LINES).

M7756

FALL

RISE

THERMOSTAT SUBBASE SYSTEM COMPONENTS

MOTOR

OUTDOOR

FAN RELAY 1

DEFROST SWITCH

RELAY

DEFROST

RELAY

TM1 TM2

OUTDOOR

FAN RELAY 2

DEFROST

SWITCH

OUTDOOR

THERMOSTAT 1

OUTDOOR

FAN RELAY 3

1ST STAGE

SHORT

CYCLE

CONTROL

2ND STAGE

SHORT

CYCLE

CONTROL

1ST STAGE LOW

PRESSURE LIMIT

2ND STAGE LOW

PRESSURE LIMIT

TIME DELAY

HEATER

ECONOMIZER

RELAY

ENTHALPY

CONTROL

ECONO-

MIZER

RELAY 2

ECONOMISER

RELAY 1

TIME DELAY

RELAY

DEFROST

RELAY

COOL CHANGEOVER

VALVE

EMERGENCY

HEAT RELAY

AUXILIARY

HEAT RELAY

SYSTEM

SWITCH

OFF

COOL

HEAT

EM. HT.

AUX. HEAT

LED (GREEN)

EM. HEAT

LED (RED)

FAN

SWITCH

AUTO

DEFROST

RELAY

CONTACT

DEFROST

RELAY

CONTACT

C815 OUTDOOR

THERMISTOR

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8140

Fig. 119. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

Fig. 120. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

FALL

(HOT)

FALL

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

H1 ANTICIPATOR

ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

RESET

HEATER

H2 ANTICIPATOR

FAN SWITCH

AUTO

C815A

OUTDOOR

THERMISTOR

AUX. HT. RELAY

FAN RELAY

SERVICE

EM. HT. RELAY

COMPRESSOR

CONTACTOR

HEAT CHANGEOVER

RELAY

SERVICE LED

(YELLOW)

EM. HT.

LED (RED)

THERMOSTAT SUBBASE SYSTEM COMPONENTS

M5955

H2 FALL

H1 FALL

(HOT) L2

FAN SWITCH

AUTO

FAN RELAY

AUX. HT. RELAY

"H" RELAY

EM. HT. RELAY

CHANGEOVER VALVE (COOL)

COMPRESSOR

CONTACTOR

C815A1039

THERMISTOR

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

EM. HT.

LED (RED)

H1/C1

ANTICIPATOR

RESET HEATER

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M3173B

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

141 60-2485—8

Fig. 121. Schematic and hookup of T874C with Q674L. Used in heat pump applications.

(HOT)

L2 1

ODT1

EHR1

ODT2

EHR2

RTD2

RTD3

RTD1

COMPRESSOR

FAILURE

HEAT CHANGEOVER

VALVE

COMPRESSOR

CONTACTOR

LACO CHP

EM. HT.

RELAY

COOL CHANGEOVER

VALVE

FAN RELAY

RTD1

FALL

RISE

AUX. HT.

LED (GRN)

EM. HT.

LED (RED)

AUTO

FAN

SWITCH

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

H2 ANTICIPATOR

H1 ANTICIPATOR

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

M7012

ANTICIPATOR

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8142

Fig. 122. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

H1 C1

FALL 5

H1/C1

ANTICIPATOR

AUTO

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

FAN RELAY

SERVICE

LED (RED)

EM. HT. LED

(YELLOW)

SERVICE

COMPRESSOR

CONTACTOR

EM. HT. RELAY

AUX. HT. RELAY

POWER SUPPLY. PROVIDE DISCONNECT

MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

(HOT)

CHANGEOVER

VALVE

FALL

M8379

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FAN

SWITCH

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

143 60-2485—8

Fig. 123. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

FALL

(HOT) L2

POWER SUPPLY. PROVIDE

DISCONNECT MEANS AND

OVERLOAD PROTECTION

AS REQUIRED.

CONNECT CHANGEOVER

RELAY TO B FOR HEAT

CHANGEOVER, TO O FOR

COOL CHANGEOVER.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

LACO CHP

ODT 1

RTD 1

EHR 1 RTD 2

ODT 2

EHR 2 RTD 3

COMPRESSOR

MONITOR

BHEAT

CHANGEOVER VALVE

COMPRESSOR

CONTACTOR

EM. HT. RELAY

COOL

CHANGEOVER VALVE

FAN RELAY

RTD 1

ANTICIPATOR

H1/C1

ANTICIAPTOR

FAN

SWITCH

AUTO

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

EM. HT.

LED (RED)

AUX. HT.

LED

(GREEN)

M1030A

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8144

Fig. 124. Schematic and hookup of T874J with Q674L. Used in heat pump applications.

FALL

C1 RISE

FALL

RISE

(HOT) L2

THERMOSTAT SUBBASE SYSTEM COMPONENTS

COMPRESSOR CONTACTOR

FAN RELAY HEAT RELAY 1

OUTDOOR

THERMOSTAT

HEAT RELAY

CONTACT 1 HEAT RELAY 2

HEAT RELAY

CONTACT 2 HEAT RELAY 3

"X" RELAY

"P" RELAY

COOL

CHANGEOVER VALVE

SYSTEM

SWITCH

EM. HT. OR

SUPL. HT.

HEAT

OFF

FAN

SWITCH

AUTO

ANTICIPATOR

C1 ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

ON MODELS INCLUDING EXTERNAL JUMPER, W2=W1 AND L=F.

EM. HT. OR

SUPL. HT.

LED (RED)

M8003

COOL

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

145 60-2485—8

Fig. 125. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

(HOT)

EM. HT.

LED (RED)

AUX. HT.

LED (GRN) AUX. HT.

RELAY

FAN RELAY

"B" RELAY

COOL CHANGEOVER

VALVE

EM. HT. RELAY

COMPRESSOR

CONTACTOR

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

H1/C1

ANTICIPATOR

FALL

AUX. HT.

RELAY

ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

TERMINAL LABELED C/X ON SOME MODELS.

W3 TERMINAL AVAILABLE ON SOME MODELS ONLY.

M3683A

AUTO

FAN

SWITCH

FALL

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8146

Fig. 126. Schematic and hookup of T874G with Q674P. Used in heat pump applications.

Fig. 127. Schematic and hookup of T874C with Q674L. Used in heat pump applications.

FALL

RISE

C1 RISE

(HOT)

L2 1

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

N.O. SWITCH INSTALLER ADDED, TO LIGHT EM. HT. LED WHEN COMPRESSOR OPERATION IS NOT NORMAL.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H1 ANTICIPATOR

H2 ANTICIPATOR

C1 ANTICIPATOR

SYSTEM

SWITCH

FAN

SWITCH

AUTO

SUPL. HT.

HEAT

COOL

FAN RELAY

COOL CHANGEOVER

VALVE

COMPRESSOR

CONTACTOR 1

HEAT RELAY 2

HEAT RELAY 1

M4722

HEAT RELAY

CONTACT 2

HEAT RELAY

CONTACT 1

HEAT RELAY 3

OUTDOOR

THERMOSTAT

FALL

SUPL. HT.

LED (RED)

FALL

AUTO

HEAT

OFF

COOL

M5652A

POWER SUPPLY. PROVIDE

DISCONNECT MEANS AND

OVERLOAD PROTECTION

AS REQUIRED.

FAN SWITCH

(HOT)

SYSTEM SWITCH

COMPRESSOR

FAILURE

FAN RELAY

LACO CHP

COMPRESSOR

CONTACTOR

EM. HT.

RELAY

COOL CHANGEOVER

VALVE

EM. HT.

LED (RED)

AUX.HT.

LED (GREEN)

RISE

FALL

C1 ANTICIPATOR

EM. HT.

ODT1

RTD1

EHR1

RTD2

ODT2

EHR2 RTD3

RTD1

H2 ANTICIPATOR

H1 ANTICIPATOR

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

147 60-2485—8

Fig. 128. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

Fig. 129. Schematic and hookup of T874G with Q674L. Used in heat pump applications.

FALL

AUTO

HEAT

OFF

COOL

M5653A

POWER SUPPLY. PROVIDE

DISCONNECT MEANS AND

OVERLOAD PROTECTION

AS REQUIRED.

FAN

SWITCH

(HOT)

SYSTEM

SWITCH

SYSTEM

MONITOR

FAN RELAY

LACO CHP

COMPRESSOR

CONTACTOR

EM. HT. RELAY

COOL CHANGEOVER

VALVE

EM. HT.

LED

(YELLOW)

AUX. HT.

LED

(GREEN)

FALL

EM. HT.

RTD1 EHR1

RTD2

ODT2

EHR2 RTD3

RTD1

H1/C1

ANTICIPATOR ODT1

SERVICE

LED (RED)

H2 ANTICIPATOR

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FALL L1

(HOT)

L2 1

FALL

RISE

H1 ANTICIPATOR

H2 ANTICIPATOR

ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

COMPRESSOR

CONTACTOR

M102A

COOL CHANGEOVER VALVE

EM. HT. RELAY AUX. HT. RELAY

FAN RELAY

EM. HT.

LED (RED)

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

FAN

SWITCH

AUTO

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8148

Fig. 130. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

FALL

(HOT)

L2 1

1POWER SUPPLY. PROVIDE DISCONNECT

MEANS AND OVERLOAD PROTECTION

AS REQUIRED.

FACTORY-INSTALLED JUMPER.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H1/C1

ANTICIPATOR

H2 ANTICIPATOR

SYSTEM

SWITCH

FAN

SWITCH

AUTO

OFF

HEAT

EM. HT.

COOL

FAN RELAY

EM. HT. RELAY

COOL

CHANGEOVER VALVE

COMPRESSOR

CONTACTOR

M1628A

COMPRESSOR

FAILURE

C815A OUTDOOR

THERMISTOR

SYSTEM

LED (GREEN)

CHECK

LED

(RED)

AUX. HT.

LED

(YELLOW)

RESET

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

149 60-2485—8

Fig. 131. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

H2 FALL

FALL

(HOT)

L2 1

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

FOR Q674L1454, IS "OFF".

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H1/C1 ANTICIPATOR

H2 ANTICIPATOR

SYSTEM

SWITCH

FAN

SWITCH

AUTO

SUPL. HT.

HEAT

COOL

COOL CHANGEOVER

VALVE

COMPRESSOR

CONTACTOR

FAN RELAY

M4723

SUPL. HT.

LED (RED)

HCR 1 HCR 2

HCR 2 HCR 3

ODT

HCR 1

RESET

HEATER

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8150

Fig. 132. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

Fig. 133. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

FALL

(HOT)

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

REMOVE JUMPER FOR INDEPENDENT CONTROL OF W1 AND E TERMINALS.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H1/C1

ANTICIPATOR

RESET

SYSTEM

SWITCH

FAN

SWITCH

AUTO

OFF

HEAT

EM. HT.

COOL

COMPRESSOR

CONTACTOR

FAN RELAY

M1858

COOL CHANGEOVER

VALVE

SEQ 1

SEQ 2

EM. HT. RELAY

HPS 4R

C815A

OUTDOOR

THERMISTOR

SYSTEM

LED

(GREEN)

EM. HT.

LED

(RED)

AUX. HT.

LED

(YELLOW)

FALL

(HOT)

L2 1

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FAN

SWITCH

AUTO

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

M2018

H1/C1

ANTICIPATOR

H2 ANTICIPATOR

FAN

RELAY

EM. HT.

RELAY

AUX. HT.

RELAY

CO W1 RELAY

COMPRESSOR

CONTACTOR

EM. HT.

LED (YEL)

RESET

LED (RED)

COMPRESSOR

FAILURE

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

151 60-2485—8

Fig. 134. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

FALL

LACO CHP

POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

(HOT)

L2 1

H1/C1

ANTICIPATOR

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

FAN SWITCH

AUTO

AUX. HT.

LED (GREEN)

EM. HT.

LED (RED)

COMP.

FAILURE

CHANGEOVER

VALVE (HEAT)

COMPRESSOR

CONTACTOR

EM. HT. RELAY

RTD 1

FAN RELAY

RTD 1 ODT 1

EHR 1 RTD 2

ODT 2

EHR 2 RDT 3

CHANGEOVER VALVE (COOL)

M106A

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8152

Fig. 135. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

Fig. 136. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

FALL

(HOT)

L2 1

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FAN

SWITCH

AUTO

SYSTEM

SWITCH

SUPL. HT.

HEAT

OFF

COOL

M2017

HCR 1

ODT HCR 1 HCR 2

FAN RELAY

COOL

CHANGEOVER VALVE

HCR 2 HCR 3

COMPRESSOR

CONTACTOR

SUPL. HT.

LED (RED)

H1/C1

ANTICIPATOR

RESET

HEATER

H2 ANTICIPATOR

FALL

(HOT)

FAN RELAY

AUX. HEAT

RELAY

COMP.

FAILURE

O.D.

STAT

C815A OUTDOOR

THERMISTOR

COOL CHANGEOVER

VALVE

COMPRESSOR

CONTACTOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

FIELD REMOVABLE JUMPER

THERMOSTAT SUBBASE SYSTEM COMPONENTS

RESET

FAN

SWITCH

AUTO

AUX. HT.

LED (GRN)

EM. HT.

LED (RED)

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

M2012

ANTICIPATOR

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

153 60-2485—8

Fig. 137. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

FALL

LACO CHP

POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

(HOT)

L2 1

H1/C1

ANTICIPATOR

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

FAN SWITCH

AUTO

AUX. HT.

LED (GREEN)

EM. HT.

LED

(RED)

CHECK

LED (RED)

COMP.

FAILURE

CHANGEOVER

VALVE (HEAT)

COMPRESSOR

CONTACTOR

EM. HT. RELAY

RTD 1

FAN RELAY

RTD 1 ODT 1

EHR 1 RTD 2

ODT 2

EHR 2 RDT 3

CHANGEOVER VALVE (COOL)

M105A

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8154

Fig. 138. Schematic and hookup of T874L with Q674B. Used in heat pump applications.

Fig. 139. Schematic and hookup of T874D with Q674F. Used in heat pump applications.

M103A

R1 NO2 S1 RELAY

S1 NC

SOLIENOID

RELAY FAN RELAY

FAN SWITCH

AUTO

AUX. HT. RELAY

COMPRESSOR

CONTACTOR

R1 NC1

R2 NO1

REVERSING

VALVE

R1 RELAY

SYSTEM SWITCH

HEAT

OFF

COOL

H1 ANTICIPATOR

H2 ANTICIPATOR

C1 ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

FIELD REMOVABLE JUMPER

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FALL

(HOT)

L2 1

RISE

H1 FALL

H2 FALL

C1 RISE

C2 RISE

(HOT)

L2 1

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H1 ANTICIPATOR

H2 ANTICIPATOR

C1 ANTICIPATOR

C2 ANTICIPATOR

SYSTEM

SWITCH

FAN

SWITCH

AUTO

OFF

2 STG. HEAT

HEAT PUMP

AUX. HT.

COOL

FAN RELAY

AUX. HT. RELAY

COOL CHANGEOVER

VALVE

COMPRESSOR

CONTACTOR 1

COMPRESSOR

RELAY

COMPRESSOR

CONTACTOR 2 M4730

HEAT PUMP

LED (GREEN)

AUX. HT

LED (RED)

11 Y2

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

155 60-2485—8

Fig. 140. Schematic and hookup of T874W with Q674L. Used in heat pump applications.

C815A OD THERMISTOR

AUX. HT. RELAY

FAN RELAY

EM. HT. RELAY

COMPRESSOR

MONITOR

HEAT CHANGEOVER

RELAY

COOL CHANGEOVER

RELAY

COMPRESSOR

CONTACTOR 1

COMPRESSOR

CONTACTOR 2

EM.HT.

AUTO

FAN SWITCH

H1 ANTICIPATOR

H2 ANTICIPATOR

H3 ANTICIPATOR

RESET

FALL

AUX. HT.

LED

(GREEN)

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

CONNECT CHANGEOVER RELAY TO 'O' TERMINAL FOR CHANGEOVER IN COOLING OR TO 'B' TERMINAL FOR CHANGEOVER IN HEATING. M1

C1 ANTICIPATOR

RISE

RISE C2 ANTICIPATOR

EM. HT.

LED (RED)

CHECK LED

(RED)

HEAT

OFF

COOL

SYSTEM

SWITCH

THERMOSTAT SUBBASE SYSTEM COMPONENTS

(HOT)

L2 1

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8156

Fig. 141. Schematic and hookup of T874C with Q674F. Used in standard applications.

Fig. 142. Schematic and hookup of T874C,D with Q674F. Used in standard applications.

FALL

RISE

(HOT)

L2 1

ANTICIPATOR

RISE

ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED.

AUTO

FAN

SWITCH

SYSTEM

SWITCH

OFF

EM. HT.

HEAT

AUTO

COOL

HEAT RELAY 1

HEAT RELAY 2

EM. HT. LED

(RED)

EM. HT. RELAY

FAN RELAY

COMPRESSOR

CONTACTOR 1

COMPRESSOR

CONTACTOR 2

M8376

THERMOSTAT SUBBASE SYSTEM COMPONENTS

ANTICIPATOR

FALL

EM. HT.

HEAT

SYSTEM

SWITCH

H1 ANTICIPATOR

H2 ANTICIPATOR

ANTICIPATOR

AUTO

COOL

M5985

POWER SUPPLY. PROVIDE DISCONECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

SYSTEM COMPONENTSSUBBASE

THERMOSTAT

OFF

AUTO

FAN

SWITCH

(HOT)

L2 1

EM. HT. RELAY

FAN RELAY

COMPRESSOR

CONTACTOR 2

COMPRESSOR

CONTACTOR 1

HEAT RELAY 1

HEAT RELAY 2

RISE

FALL

CHECK

LED (RED)

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

157 60-2485—8

Fig. 143. Schematic and hookup of T874G with Q674B. Used in heat pump applications.

Fig. 144. Schematic and hookup of T874J with Q674J. Used in heat pump applications.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

M8378

FALL 1

H1 ANTICIPATOR

FAN

SWITCH

AUTO

COMPRESSOR

CONTACTOR

FAN RELAY

FALL

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED.

RISE

ANTICIPATOR

(HOT)

RISE

AUX. HT. RELAY

AUX. HT. LED

(RED)

SYSTEM

SWITCH

OFF

AUTO

ANTICIPATOR O

COOL

CHANGEOVER VALVE

FALL

C1 RISE

H2 FALL

RISE

(HOT) L2

THERMOSTAT SUBBASE SYSTEM COMPONENTS

COMPRESSOR CONTACTOR

FAN RELAY

HEAT RELAY 1

OUTDOOR

THERMOSTAT

HEAT RELAY

CONTACT 1 HEAT RELAY 2

HEAT RELAY

CONTACT 2 HEAT RELAY 3

"X" RELAY

"P" RELAY

COOL CHANGEOVER

VALVE

SYSTEM

SWITCH

SUPL. HT.

OFF

FAN

SWITCH

AUTO

H1 ANTICIPATOR

H2 ANTICIPATOR

C1 ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

11 O

SUPP. HT.

LED (RED)

M5956

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8158

Fig. 145. Schematic and hookup of T874G with Q674F. Used in heat pump applications.

Fig. 146. Schematic and hookup of T874D with Q674F. Used in heat pump applications.

OFF

COOL

OUTDOOR

THERMOSTAT

SYSTEM

SWITCH

FAN

SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED.

M8375

EM. HT. RELAY

TIME DELAY

FAN RELAY

EM. HT.

LED (RED)

EM. HT.

HEAT

AUTO

SUP. ELEC.

HT. RELAY

DEFROST

RELAY

COMPRESSOR

CONTACTOR INTERNAL

THERMOSTAT

COOL CHANGEOVER

VALVE

HIGH

PRESSURE

SWITCH

OVERLOAD

AUTO

ANTICIPATOR

C1 ANTICIPATOR

C1 RISE

FALL

EM. HT. RELAY

FALL

L2 (HOT) L1

FAN RELAY

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FALL

AUTO

COOL

SYSTEM

SWITCH

H1 ANTICIPATOR

AUTO

FAN

SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED. M7010

THERMOSTAT SUBBASE SYSTEM COMPONENTS

ANTICIPATOR

SUPL.

HEAT

LED

(RED)

SUPL. HT.

HEAT

OFF

RVR RVR

EHR EHR

COMPRESSOR

CONTACTOR 1

DFR 2

REVERSING

RELAY

FAN RELAY

(HOT)

ODT 3

HEAT

RELAY 2

HEAT RELAY 1

ODT 2

HEAT RELAY 3

SUPL. HT.

RELAY

DFR 2 COMPRESSOR

CONTACTOR 2

LPCO

FALL

RISE

ANTICIPATOR

RISE C2

EHT

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

159 60-2485—8

Fig. 147. Schematic and hookup of T874G with Q674F. Used in heat pump applications.

Fig. 148. Schematic and hookup of T874G with Q674F. Used in heat pump applications.

FALL

AUTO

COOL

SYSTEM

SWITCH

ANTICIPATOR

AUTO

FAN

SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

CONNECT TO Y OR W TERMINAL WITH FACTORY INSTALLED JUMPER. M7024

THERMOSTAT SUBBASE SYSTEM COMPONENTS

ANTICIPATOR

EM. HT.

HEAT

OFF

FALL

RISE

ANTICIPATOR

RISE C1

(HOT)

MODE SIGNAL

COOL

CHANGEOVER

VALVE

COMPRESSOR

CONTACTOR

EM. HT. RELAY

HEAT RELAY 1 HEAT RELAY 2

FAN RELAY

MODE SIGNAL

AUX. HT.

LED (GRN)

EM. HT.

LED (YEL)

SERVICE

LED (RED)

3JUMPER FACTORY INSTALLED.

OFF

COOL

DEFROST

RELAY

FAN

SWITCH

SYSTEM

SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M8382

AUX. HT. RELAY

EM. HT. RELAY

EM. HT.

LED

(RED)

EM. HT.

HEAT

AUTO

COOL CHANGEOVER

VALVE

BLOWER SPEED

RELAY

DEFROST

RELAY

BLOWER RELAY

COOL

CONTRACTOR

LOCKOUT

THERMOSTAT

AUTO

H1 ANTICIPATOR

H2 ANTICIPATOR

ANTICIPATOR

C1 RISE

RISE

FALL

H2 W2

(HOT)

L2 1

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8160

Fig. 149. Schematic and hookup of T874C with Q674F. Used in heat pump applications.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FALL

H1 ANTICIPATOR

FALL

ANTICIPATOR

EMR4 2R

EMR4

EMR2

THERMAL SWITCHES

FOR HEATING

ELEMENTS HTR 1

RISE

HTR 3

HTR 2

OUTDOOR

THERMOSTAT

EMR3

(HOT)

(HOT) L2

RISE

ANTICIPATOR

EM. HT. LED

EMR1

EM. HT. RELAY

POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

OPTIONAL FIELD WIRE JUMPER TO ALLOW

SINGLE SYSTEM TRANSFORMER.

FOR Q674F1048, DELETE C2 STAGE.

M8380

SYSTEM

SWITCH

OFF

EM. HT.

HEAT

AUTO

COOL

FAN

SWITCH

AUTO

3R1

4R2 2R2

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

161 60-2485—8

Fig. 150. Schematic and hookup of T874G with Q674F. Used in heat pump applications.

HOT

EM. HEAT

LED (RED)

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

H1 ANTICIPATOR

1POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED. M2852A

FALL

AUTO

FAN SWITCH

OUTDOOR

THERMOSTAT SUPL. ELEC.

HT. RELAY

COOL CHANGEOVER VALVE

COMPRESSOR

CONTACTOR

OVERLOAD

SWITCH

INTERNAL

THERMOSTAT

HI PRESSURE

SWITCH

FAN

RELAY

EM. HT. RELAY

CONTACT TIME DELAY

FAN RELAY

TIME DELAY

FAN RELAY

SYSTEM

MONITOR

AUTO

FALL

H2 ANTICIPATOR

RISE

ANTICIPATOR

REMOVE FACTORY INSTALLED V-VR JUMPER WHEN CONNECTING

A TWO TRANSFORMER SYSTEM.

HOT

L2 1

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8162

Fig. 151. Schematic and hookup of T874G with Q674F. Used in heat pump applications.

H1 FALL

H2 FALL

RISE

C1 RISE

(HOT)

(HOT) L2

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

OPTIONAL FIELD WIRE JUMPER TO CYCLE W2 WITH H1 IN EM. HT.

(FASTER RESPONSE).

THERMOSTAT SUBBASE SYSTEM COMPONENTS

M4710

ANTICIPATOR

SYSTEM

SWITCH

FAN

SWITCH

AUTO

OFF

HEAT

EM. HT.

AUTO

COOL

EM. HT.

LED

(RED)

EM. HT. RELAY

CONTACT 1

T6031 REFRIGERATON/

TEMPERATURE

CONTROLLER

EM. HT.

EM. HT. RELAY

COMPRESSOR

CONTACTOR

SEQUENTIAL

RELAY

FANREVERSING

SOLENOID

COM

EM.

HT.

FAN

R8233B

CDF

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

163 60-2485—8

Fig. 152. Schematic and hookup of T874D with Q674F. Used in standard applications.

Fig. 153. Schematic and hookup of T874G with Q674F. Used in heat pump applications.

OFF

SYSTEM

SWITCH

FAN SWITCH

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

M8377

HEAT RELAY 2

COMPRESSOR

CONTRACTOR 1

EM. HEAT

LED (RED)

EM. HT.

HEAT

AUTO

HEAT RELAY

COMPRESSOR

CONTRACTOR 2

AUTO

H1 ANTICIPATOR

H2 ANTICIPATOR

C2 ANTICIPATOR

RISE

FALL

FAN RELAY

EM. HT. RELAY

(HOT)

2FACTORY SUPPLIED FIELD INSTALLED JUMPER TO E-X2 FOR CONSTANT POWER TO EM HT LIGHT IN EM HT POSITION.

3OPTIONAL FIELDWARE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER.

C1 ANTICIPATOR

THERMOSTAT SUBBASE SYSTEM COMPONENTS

COOL

OFF

COOL

OUTDOOR

THERMOSTAT

FAN

SWITCH

SYSTEM

SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M8381

AUX. HT. RELAY

CONTACT

AUX. HT. RELAY

EM. HT. LED

(RED)

EM. HT.

HEAT

AUTO

COOL CHANGEOVER

VALVE

FAN RELAY

COMPRESSOR

CONTACTOR

AUTO

ANTICIPATOR

H2 ANTICIPATOR

C1 ANTICIPATOR

C1 RISE

RISE

EM. HT.

RELAY

FALL

(HOT)

L2 1

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8164

Fig. 154. Schematic and hookup of T874G with Q674F. Used in heat pump applications.

FALL

COM

COMPRESSOR

CONTACTOR

EM. HT.

HEAT

AUTO

COOL

COMP. FAULT

LED (YELLOW)

SYSTEM

SWITCH

FAN

SWITCH

AUTO

1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED.

OPTIONAL FIELD WIRE JUMPER TO CYCLE W2 WITH H1

IN EM. HEAT(FASTER RESPONSE).

H2 ANTICIPATOR

CDF RS

FAN

(HOT) L2

EM. HT. RELAY

FAN

REVERSING

SOLENOID

T6031

REFRIGERATION

TEMPERATURE

CONTROLLER

EM. HT. RELAY

CONTACT 1

EM. HT.

(HOT)L2

EM. HT.

LED (RED)

H1 ANTICIPATOR

FALL

H1 ANTICIPATOR

RISE

SEQUENTIAL

RELAY

M2858

R8233B

THERMOSTAT SUBBASE SYSTEM COMPONENTS

OFF

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

165 60-2485—8

Fig. 155. Schematic and hookup of T874G with Q674F. Used in heat pump applications.

FALL

(HOT)

L2 1

RTD1 OTD1

EHR1

ODT2

EHR2

RTD2

RTD3

RTD1

SYSTEM

MONITOR

FAN

RELAY

COOL

CHANGEOVER VALVE

EM. HT.

RELAY

LACO

COMPRESSOR

CONTACTOR CHP

H1 FALL

H1 ANTICIPATOR

ANTICIPATOR

CHANGEOVER

RISE

ANTICIPATOR

OFF

COOL

AUTO

HEAT

EM. HT.

SYSTEM

SWITCH

AUTO

FAN

SWITCH

AUX. HT.

LED (GRN)

EM. HT.

LED (RED)

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

W3 TERMINAL ON SELECT MODELS.

M1589

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8166

Fig. 156. Schematic and hookup of T874G with Q674F. Used in heat pump applications.

Fig. 157. Schematic and hookup of T874G with Q674F. Used in heat pump applications.

COMPRESSOR

FAILURE

FALL

(HOT)L2

RISE

ANTICIPATOR

RISE

OFF

EM. HT.

SYSTEM

SWITCH

FAN

SWITCH

C1 ANTICIPATOR

H2 ANTICIPATOR

HEAT

AUTO

COOL

EM. HT. LED

(RED)

AUX. HT.

RELAY

CONTACT EM. HT.

RELAY

COOL

CHANGEOVER VALVE

FAN RELAY

OUTDOOR

THERMOSTAT

EM. HT. LED

(GREEN)

AUX. HT. RELAY

COMPRESSOR CONTACTOR

M5720

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

SYSTEM COMPONENTSSUBBASETHERMOSTAT

COMPRESSOR

CONTACTOR

H2 ANTICIPATOR

M2860

AUTO

FAN SWITCH

H1 ANTICIPATOR

C1 ANTICIPATOR

RISE

FALL

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

AUTO

TIME DELAY

RELAY 2

FAN RELAY

COOL CHANGEOVER

VALVE

LOCKOUT

RELAY

HI PRESSURE

SWITCH

EM. HT.

LED (RED)

CHECK LED

(GREEN)

TIME DELAY

RELAY 1

DEFROST

RELAY

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

(HOT)

RISE

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

167 60-2485—8

Fig. 158. Schematic and hookup of T874G with Q674F. Used in heat pump applications.

OFF

EM. HT.

SYSTEM

SWITCH

HEAT

AUTO

COOL AUX. HT. LED (GREEN)

M5721

C1 ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

RISE

FALL

C1 RISE

H2 ANTICIPATOR

FALL

H1 ANTICIPATOR

AUTO

FAN

SWITCH

EM. HT. LED

(RED)

(HOT) L2

AUX. HT. RELAY

COMPRESSOR CONTACTOR

B TERMINAL ON SELECT MODELS.

HEAT CHANGEOVER VALVE

FAN RELAY

EM. HT. RELAY

COOL CHANGEOVER VALVE

COMPRESSOR

FAILURE

SYSTEM COMPONENTSSUBBASETHERMOSTAT

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8168

Fig. 159. Schematic and hookup of T874G with Q674J. Used in heat pump applications.

Fig. 160. Schematic and hookup of T874G with Q674J. Used in heat pump applications.

(HOT) L2

H1 FALL

H1 ANTICIPATOR

FALL

RISE

C1 ANTICIPATOR

OFF

AUTO

SYSTEM

SWITCH

FAN SWITCH

OUTDOOR

THERMOSTAT

OFF

AUTO

EM.HT.

EM. HT. LED

(RED)

LIMIT

COMPRESSOR

CONTACTOR

HEAT RELAY

CONTACT

EM. HT.

RELAY

AUX. HT. RELAY

COOL CHANGEOVER VALVE

FAN RELAY

M5722

HEAT RELAY

CONTACT

SYSTEM COMPONENTS

SUBBASETHERMOSTAT

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

H2 ANTICIPATOR

EM. HT.

AUX. HT. RELAY

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

RISE

COMPRESSOR

CONTACTOR

FALL

SYSTEM COMPONENTSSUBBASETHERMOSTAT

H1 ANTICIPATOR

(HOT)

L2 1

FALL

FAN RELAY

COOL CHANGEOVER VALVE

H2 ANTICIPATOR

C1 ANTICIPATOR

FAN

SWITCH

AUTO

SYSTEM

SWITCH

AUTO

OFF

EM. HT.

LED (RED)

M5723

EM. HT. RELAY

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

169 60-2485—8

Fig. 161. Schematic and hookup of T874G with Q674J. Used in heat pump applications.

H2 ANTICIPATOR

SUPL. HT.

LED (RED)

M5724

POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

SYSTEM COMPONENTSSUBBASETHERMOSTAT

(HOT)

FALL

RISE

H1 ANTICIPATOR

C1 ANTICIPATOR

SYSTEM

SWITCH

SUPL. HT.

OFF

FAN

SWITCH

AUTO

ON FAN RELAY

COOL CHANGEOVER VALVE

OUTDOOR

THERMOSTAT

EM. HT. RELAY 1

EM. HT. RELAY

CONTACT 1

EM. HT. RELAY 2

EM. HT. RELAY

CONTACT 2 EM.HT.

RELAY 3

COMPRESSOR

CONTACTOR 1

N.O. SWITCH — INSTALLER ADDED, TO LIGHT EM. HT. LED

WHEN COMPRESSOR OPERATION IS NOT NORMAL.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8170

Fig. 162. Schematic and hookup of T874G with Q674J. Used in heat pump applications.

FALL

EM. HT.

LED (RED)

(HOT)

AUX. HT. LED

(GREEN)

M5725

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

SYSTEM COMPONENTSSUBBASETHEROMSTAT

FALL

RISE

10 Y

ANTICIPATOR

RESET HEATER

H1 ANTICIPATOR

SYSTEM SWITCH

EM. HT.

AUTO

OFF

FAN SWITCH

AUTO

C815A OUTDOOR

THERMISTOR

FAN RELAY

COOL

CHANGEOVER VALVE

OUTDOOR

THERMOSTAT

AUX. HT. RELAY

EM. HT. RELAY

COMPRESSOR

CONTACTOR

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

171 60-2485—8

Fig. 163. Schematic and hookup of T874G with Q674C. Used in standard applications.

FALL

RISE

(HOT)

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

H2 HAS 10¡F FIXED SETBACK FROM H1 ON T874G1485, 0-12¡F

ADJUSTABLE ON T874G1535.

RESET IN MOMENTARY POSITION, SPRING RETURN TO OFF UPON

SWITCH RELEASE.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

ANTICIPATOR

FAN

SWITCH

AUTO

SYSTEM

SWITCH

AUTO

OFF

RESET

RESET CIRCUIT

COMPRESSOR

RELAY

SERVICE LED (RED)

ON LED (YELLOW)

COOL

CHANAGEOVER VALVE

HEAT RELAY 2

FAN RELAY

HEAT RELAY 1

HEAT DAMPER

M1820C

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8172

Fig. 164. Schematic and hookup of T874H with Q674C. Used in standard applications.

Fig. 165. Schematic and hookup of T874L with Q674C. Used in heat pump applications.

FALL

(HOT)

OFF

FAN SWITCH

SYSTEM SWITCH

ANTICIPATOR

AUTO

M5726

POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

SYSTEM COMPONENTSSUBBASETHERMOSTAT

AUTO

RISE

R-L JUMPER SUPPLIED BY HONEYWELL.

ANTICIPATOR

MALFUNCTION

LED (RED) HEAT CHANGEOVER

VALVE

MALFUNCTION

SWITCH

FAN RELAY

COMPRESSOR

CONTACTOR

COOL CHANGEOVER

VALVE

(HOT)

L2 1

RISE

H1 ANTICIPATOR

FAN

SWITCH

AUTO

M5727

POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

SYSTEM COMPONENTS

SUBBASETHERMOSTAT

SYSTEM

SWITCH

AUTO

OFF

H2 ANTICIPATOR

FIELD REMOVABLE JUMPER.

H1 AND C1 ARE DPST SWITCHES.

FALL

H1 FALL

ANTICIPATOR

R1 N.O.2 S1 RELAY

SOLENOID RELAY S1 N.C.

FAN RELAY

AUX. HT. RELAY

R1 N.C.1

COMPRESSOR

CONTACTOR

R2 N.O. 1

R1 RELAY

REV. VALVE

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

173 60-2485—8

Fig. 166. Schematic and hookup of T874D with Q674F. Used in standard applications.

FALL

(HOT)

L2 1

H1 ANTICIPATOR

OFF

EM. HT.

SYSTEM

SWITCH

FAN

SWITCH

HEAT

AUTO

COOL

AUTO

M5728

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

SYSTEM COMPONENTSSUBBASETHERMOSTAT

FALL

RISE

(HOT)

L2 1

HEAT RELAY 1

HEAT RELAY 2

EM. HT. RELAY

FAN RELAY

COMRESSOR CONTACTOR 1

AUX. HT. LED

(GREEN)

EM. HT. LED

(RED)

COMRESSOR CONTACTOR 2

SYSTEM

MONITOR

C1 ANTICIPATOR

C2 ANTICIPATOR

H2 ANTICIPATOR

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8174

Fig. 167. Schematic and hookup of T874G with Q674F. Used in heat pump applications.

M1592A

(HOT) L1 L2

LACO CHP

RODT 1

RTD 1 EHR 1 RTD 2

ODT 2

EHR 2 RTD 3

COMPRESSOR

FAILURE

FAN RELAY

COMPRESSOR

CONTACTOR

HEAT

CHANGEOVER

VALVE EM. HT.

RELAY

RTD 1

AUX. HT.

LED (GREEN)

EM. HT.

LED (RED)

FAN SWITCH

AUTO

SYSTEM

SWITCH

EM. HT.

HEAT

AUTO

OFF

COOL

FALL

FALL 2

H1 ANTICIPATOR

ANTICIPATOR

RISE

FALL

ANTICIPATOR

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

EHT1

CHANGEOVER

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

175 60-2485—8

Fig. 168. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

FALL

(HOT)

EM. HT.

LED (RED)

AUX. HT.

LED (GRN)

AUX. HT. RELAY

EM. HT. RELAY

HEAT

CHANGEOVER

VALVE

W1 RELAY

COMPRESSOR

RELAY

W3 RELAY

COOL CHANGEOVER

VALVE

COMPRESSOR

MONITOR

FAN RELAY

FALL

ANTICIPATOR

C ANTICIPATOR

ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

REMOVE JUMPER WHEN W1 RELAY IS USED.

FACTORY-INSTALLED JUMPER.

M5067

FAN

SWITCH

AUTO

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8176

Fig. 169. Schematic and hookup of T874G with Q674F. Used in heat pump applications.

FALL

RISE

(HOT)

RISE 1

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED.

TERMINAL LABELED C/X ON SOME MODELS.

W3 TERMINAL ON SOME MODELS ONLY.

C1 ANTICIPATOR

H1 ANTICIPATOR FAN SWITCH

AUTO

SYSTEM

SWITCH

AUTO

HEAT

OFF

COOL

AUX. HT. RELAY

FAN RELAY

EM. HT. RELAY

B RELAY

M5986A

THERMOSTAT SUBBASE SYSTEM COMPONENTS

COMPRESSOR

CONTACTOR

EM. HT.

LED (RED)

AUX. HT.

LED (GREEN)

COOL CHANGEOVER

VALVE

FALL

ANTICIPATOR

AUX HT. RELAY

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

177 60-2485—8

Fig. 170. Schematic and hookup of T874G with Q674F. Used in heat pump applications.

FALL

RISE

(HOT)

RISE

POWER SUPPLY. PROVIDE DISCONNECT

MEANS AND OVERLOAD PROTECTION AS REQUIRED.

ON SOME MODELS, Y TERMINAL MAY BE LABELED Y1.

EMERGENCY HEAT RUNS CONTINUOUSLY WHEN SWITCH IN IN EM. HT. POSITION.

C1 ANTICIPATOR

H1 ANTICIPATOR FAN SWITCH

AUTO

SYSTEM

SWITCH

AUTO

HEAT

OFF

COOL

AUX. HT. RELAY

FAN RELAY

EM. HT.

RELAY

B RELAY

M5987A

THERMOSTAT SUBBASE SYSTEM COMPONENTS

COMPRESSOR

CONTACTOR

EM. HT.

LED (RED)

AUX. HT.

LED (GREEN)

FALL

ANTICIPATOR

W3 RELAY W1 RELAY

COOL

CHANGEOVER

VALVE

COMPRESSOR

FAULT

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8178

Fig. 171. Schematic and hookup of T874J with Q674J. Used in heat pump applications.

Fig. 172. Schematic and hookup of T874H with Q674B. Used in heat pump applications.

FALL

C1 RISE

(HOT)

L2 1

H1 ANTICIPATOR

OFF

EM. HT.

SYSTEM

SWITCH

FAN

SWITCH

AUTO

EM. HT. LED

(RED)

FAN RELAY

M5729

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

SYSTEM COMPONENTS

SUBBASE

THERMOSTAT

H2 FALL

RISE

EXTERNAL JUMPER SUPPLIED BY HONEYWELL.

H2 ANTICIPATOR

C1 ANTICIPATOR

COMPRESSOR

CONTACTOR

O.D.T.

HCR1

"X" RELAY

"P" RELAY

COOL CHANGEOVER

VALVE

HCR2

HCR2 HCR3

FALL

RISE

(HOT)

L2 1

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H1 ANTICIPATOR

C1 ANTICIPATOR SYSTEM

SWITCH

FAN

SWITCH

AUTO

OFF

HEAT

COOL

CHANGEOVER

VALVE

COMPRESSOR

CONTACTOR M1401

FAULT

LED

(RED)

CHECK

FILTER

LED (YELLOW)

FAN RELAY

RISE

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

179 60-2485—8

Fig. 173. Schematic and hookup of T874H with Q674C. Used in heat pump applications.

Fig. 174. Schematic and hookup of T874G with Q674J. Used in heat pump applications.

FALL

RISE

(HOT)

L2 1

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H1 ANTICIPATOR

C1 ANTICIPATOR SYSTEM

SWITCH

FAN

SWITCH

AUTO

OFF

AUTO

COOL

CHANGEOVER

VALVE

COMPRESSOR

CONTACTOR M1400

FAULT

LED

(RED)

CHECK

FILTER

LED (YELLOW)

FAN RELAY

RISE

FALL

RISE

(HOT)

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED.

REMOVABLE JUMPER.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

ODA

SYSTEM

SWITCH

FAN

SWITCH

AUTO

OFF

EM. HT.

AUTO

EM.. HT. RELAY

AUX. HT. RELAY

M1403

COMPRESSOR

CONTACTOR

COOL CHANGEOVER

VALVE

"F" RELAY

C815A

OUTDOOR

THERMISTOR

FAN RELAY

EM. HT.

LED (RED)

AUX. HT.

LED (GREEN)

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8180

Fig. 175. Schematic and hookup of T874G with Q674J. Used in heat pump applications.

Fig. 176. Schematic and hookup of T874G with Q674C. Used in standard applications.

FALL L1

(HOT)

L2 1

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FAN

SWITCH

AUTO

SYSTEM

SWITCH

SUPL. HT.

OFF

M2112A

H1 ANTICIPATOR

COOL

CHANGEOVER VALVE

FAN RELAY

H.C.R. 1

H.C.R. 1 H.C.R.2

H.C.R. 2 H.C.R.3

COMPRESSOR

CONTACTOR

FALL

RISE

C1 ANTICIPATOR

ANTICIPATOR

RISE

HEAT PUMP

(GRN)

DEFROST

(RED)

MANUAL

(RED)

AUTO

(YEL)

O.D.T.

FALL

(HOT)

H1 ANTICIPATOR

OFF

AUTO

SYSTEM

SWITCH

FAN SWITCH

AUTO

FAN RELAY

M5730

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

SETBACK STAGE OFFSET 12°F (7°C) FROM H1 STAGE.

LEDS ON SOME MODELS.

SYSTEM COMPONENTSSUBBASETHERMOSTAT

SETBACK

FALL

RISE

C1 RISE

COMPRESSOR

CONTACTOR

OPEN-NIGHT

CLOSED-DAY

C1 ANTICIPATOR

SETBACK RELAY

COOL

CHANGEOVER VALVE

LED X1

LED

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

181 60-2485—8

Fig. 177. Schematic and hookup of T874G,H with Q674C. Used in standard applications.

Fig. 178. Schematic and hookup of T874N with Q674F. Used in heat pump applications.

FALL

(HOT)

FALL

M114C

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

USE EITHER 'B' OR 'O' ONLY FOR SYSTEM CHANGEOVER. 0.8A AT 30 VAC MAXIMUM LOAD CURRENT.

SECOND STAGE HEAT MAKES 12oF (7oC) AFTER FIRST STAGE HEAT TO PROVIDE SETBACK

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FAN

SWITCH

AUTO

SYSTEM SWITCH

RESET LED

(RED)

OFF

AUTO

H1 ANTICIPATOR

FAN RELAY

COOL

CHANGEOVER VALVE

HEAT CHANGEOVER

VALVE

COMPRESSOR

CONTACTOR

C1 ANTICIPATOR

RISE

LOCKOUT

(RESET) RELAY

FALL

RISE

FALL

M18623

H1 ANTICIPATOR

H2 ANTICIPATOR

C1 ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

SYSTEM

SWITCH

HEAT

EM.HT.

OFF

COOL

AUTO

FAN

SWITCH

SERVICE

LED (RED)

EM, HT. LED

(YELLOW)

AUX.HT. RELAY

FAN RELAY

CHANGEOVER RELAY

COMPRESSOR RELAY

EM.HT. RELAY

THERMOSTAT SUBBASE SYSTEM COMPONENTS

(HOT)

L2 1

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8182

Fig. 179. Schematic and hookup of T874N with Q674F. Used in heat pump applications.

(HOT)

EM. HT.

LED (RED)

CHECK

LED

(GREEN)

FAN RELAY

EM. HT.

RELAY

COMPRESSOR

CONTACTOR

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

ANTICIPATOR

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M3686

FALL

RISE L

HEAT

RELAY 3

EM.HT. RELAY

CONTACT

OUTDOOR

THERMOSTAT

AUTO

FAN SWITCH

OPTIONAL

COMPRESSOR

FAILURE DEVICE

DEFROST

RELAY REVERSING

VALVE

EM.HT. RELAY

CONTACT

HIGH

PRESSURE

SWITCH

HEAT

RELAY 1

HEAT

RELAY 2

AUTO

FALL

ANTICIPATOR

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

183 60-2485—8

Fig. 180. Schematic and hookup of T874A,D with Q674J. Used in heat pump applications.

FALL

(HOT)

FALL

RISE

M5957

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

FILTER LED ON SOME MODELS.

C2 ANTICIPATOR

C1 ANTICIPATOR

SYSTEM

SWITCH

EM. HT.

AUTO

OFF

FILTER

LED

(YELLOW)

R-3

R-6

RANDOM START

R-8 (OPT.)

R-5

R-5 T2

(HEAT PUMP

OPERATION) R-10

(BIOLERLESS

OPERATION ) R-11

EM. HT. RELAY

ELEC. HT. RELAY

STG. 2

R-10

R-2

R-1

FAN RELAY

R-6

OVERLOADR-6

COMPRESSOR

CONTACTOR

R-8

R-10

R-11

R-11 CHANGEOVER VALVE ELEC. HT.

RELAY STG. 1

FAN DELAY

RELAY

EM. HT.

LED

(RED)

ANTICIPATOR

SYSTEM COMPONENTS

SUBBASE

THERMOSTAT

FAN

SWITCH

AUTO

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8184

Fig. 181. Schematic and hookup of T874K with Q674C. Used in heat pump applications.

Fig. 182. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

FALL

(HOT)

H2 FALL

FALL

RISE

COMPRESSOR

FAULT

REVERSING

VALVE

FAN RELAY

COMPRESSOR

RELAY

TIME

CLOCK

FAN

SWITCH

AUTO

SYSTEM

SWITCH

OFF

AUTO

COMPRESSOR

FAULT LED (RED)

ANTICIPATOR

THERMOSTAT SUBBASE SYSTEM COMPONENT

M18587

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

FAN

SYSTEM

SWITCH

COOL

HEAT

H1/C

ANTICIPATOR

FALL

M3951

AUTO

FAN

SWITCH

EM. HT.

LED (YELLOW)

SERVICE

LED (RED)

COMPRESSOR

FALL

AUX. HT.

OUTDOOR

RESET

EM. HT.

OFF

EM. HT.

W89

HEAT

PUMP

CONTROL

PANEL

COOL/HEAT

ANTICIPATOR

RESET

SERVICE

LIGHT

EM. HT. LIGHT

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

185 60-2485—8

Fig. 183. Schematic and hookup of T874G with Q674J. Used in heat pump applications.

Fig. 184. Schematic and hookup of T874A,F with Q674G. Used in standard applications.

(HOT)

FAN RELAY

SYSTEM

SWITCH

OFF

EM. HT.

ANTICIPATOR

FALL

1POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

M3950

AUTO

FAN

SWITCH

RISE

ANTICIPATOR

RISE

EM. HT.

LED (RED)

AUX. HT.

LED (GREEN)

COMPRESSOR

CONTACTOR

COMPRESSOR

FAILURE

FALL COOL CHANGEOVER

VALVE

2BH

O. D. S.

1BH SH

1BH

ANTICIPATOR

THERMOSTAT SUBBASE SYSTEM COMPONENTS

(HOT)

SYSTEM

SWITCH

OFF

ANTICIPATOR

FALL

1POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED. M3953

RISE

ANTICIPATOR

RISE

AUTO

COMPRESSOR

CONTACTOR 2

FALL

HEAT RELAY 1

ANTICIPATOR

HEAT RELAY 2

COMPRESSOR

CONTACTOR 1

(HOT)

ANTICIPATOR

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FAN

SWITCH

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8186

Fig. 185. Schematic and hookup of T874D with Q674E. Used in standard applications.

Fig. 186. Schematic and hookup of T874D with Q674G. Used in standard applications.

(HOT)

SYSTEM

SWITCH

AUTO

ANTICIPATOR

FALL

1POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

M3954

RISE

ANTICIPATOR

RISE

COOL

COMPRESSOR

CONTACTOR 2

FALL

HEAT RELAY

ANTICIPATOR

HEAT RELAY 2

COMPRESSOR

CONTACTOR 1

(HOT)

AUTO

FAN

SWITCH

FAN RELAY

IGNITION

RELAY

OFF

HEAT B

ANTICIPATOR

THERMOSTAT SUBBASE SYSTEM COMPONENTS

(HOT)

SYSTEM

SWITCH

OFF

ANTICIPATOR

FALL

1POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED. M3955

RISE

ANTICIPATOR

RISE

AUTO

COMPRESSOR

CONTACTOR 2

FALL

HEAT RELAY 1

ANTICIPATOR

HEAT RELAY 2

COMPRESSOR

CONTACTOR 1

(HOT)

FAN RELAY

ANTICIPATOR

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FAN

SWITCH

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

187 60-2485—8

Fig. 187. Schematic and hookup of T874C with Q674B. Used in standard applications.

Fig. 188. Schematic and hookup of T874D with Q674G. Used in standard applications.

SYSTEM

SWITCH

OFF

ANTICIPATOR

FALL

1POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED. M3956

RISE

ANTICIPATOR COOL

FALL

HEAT RELAY 1

HEAT RELAY 2

(HOT)

HI SPEED

FAN RELAY

LO SPEED

FAN RELAY

HIGH

TEMP.

SWITCH

HIGH

PRESSURE

SWITCH

HIGH

LOW

FAN

SWITCH

HEAT

ANTICIPATOR

COOL

CONTACTOR

LOCKOUT

RELAY

THERMOSTAT SUBBASE SYSTEM COMPONENTS

(HOT)

SYSTEM

SWITCH

ANTICIPATOR

FALL

1POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED. M3958

RISE

ANTICIPATOR

RISE

AUTO

COMPRESSOR

CONTACTOR 2

FALL

HEAT RELAY 1

ANTICIPATOR

HEAT RELAY 2

COMPRESSOR

CONTACTOR 1

(HOT)

FAN RELAY

ANTICIPATOR

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FAN

SWITCH

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8188

Fig. 189. Schematic and hookup of T874F with Q674D. Used in standard applications.

Fig. 190. Schematic and hookup of T874C with Q674L. Used in heat pump applications.

FALL

M3960

FALL

ANTICIPATOR

M839

MOTOR

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FAN

SWITCH

SYSTEM

SWITCH

(HOT)

FAN RELAY

SYSTEM

SWITCH

OFF

EM. HT.

ANTICIPATOR

FALL

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

OPTIONAL REMOVABLE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER.

WIRE JUMPER FOR SERVICE LIGHT. M3978

AUTO

FAN

SWITCH

ANTICIPATOR

RISE EM. HT. LED

(YELLOW)

HEAT

SERVICE

LED (RED)

COMPRESSOR

CONTACTOR

FALL

O. D. S.

ANTICIPATOR

THERMOSTAT SUBBASE SYSTEM COMPONENTS

COOL

COOL CHANGEOVER

VALVE

C815A

OUTDOOR THERMISTOR

EM. HT.

EM. HT. RELAY

IN STAT

HI PR

SERVICE

RELAY

ELEC. HT. RELAY

RESET

(HOT)

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

189 60-2485—8

Fig. 191. Schematic and hookup of T874R with Q674B. Used in heat pump applications.

Fig. 192. Schematic and hookup of T874D with Q674C. Used in standard applications.

OFF

H1/C1

ANTICIPATOR

FALL

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M3965

H2 W2

HEAT

FALL

AUX. HT. RELAY

"Z" RELAY

(HOT)

FAN RELAY

AUTO

CONT.

FAN

SWITCH

ANTICIPATOR

COOL

RELAY

COOL

THERMOSTAT SUBBASE SYSTEM COMPONENTS

SYSTEM

SWITCH

C1 LO

HEAT RELAY

COOL CHANGE-

OVER VALVE

ANTICIPATOR

FALL

1POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE. M3959

RISE

ANTICIPATOR

RISE

AUTO

COMPRESSOR

CONTACTOR 2

FALL

HEAT RELAY 1

ANTICIPATOR

HEAT RELAY 2

COMPRESSOR

CONTACTOR 1

(HOT)

RFAN RELAY

AUTO

OFF

SERVICE

LED (RED)

FILTER

LED

(YELLOW) X

MOMENTARY

CIRCUIT

ANTICIPATOR

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FAN

SWITCH

SYSTEM

SWITCH

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8190

Fig. 193. Schematic and hookup of T874D with Q674E. Used in standard applications.

Fig. 194. Schematic and hookup of T874G with Q674F. Used in heat pump applications.

FALL

(HOT)

HEAT RELAY 2

HEAT RELAY 1

OFF

HEAT

COOL

AUTO

SYSTEM

SWITCH

ANTICIPATOR

C1 ANTICIPATOR

FAN

SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

JUMPER RH, RC FOR SINGLE TRANSFORMER.

M3203B

(HOT)

FAN RELAY

CHANGEOVER

RELAY (COOL)

CHANGEOVER

RELAY (HEAT)

COMPRESSOR

CONTACTOR 2

COMPRESSOR

CONTACTOR 1

FALL

C2 ANTICIPATOR

RISE

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H2 ANTICIPATOR

(HOT)

FAN RELAY

SYSTEM

SWITCH

OFF

EM. HT.

ANTICIPATOR

FALL

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M3977

AUTO

FAN

SWITCH

RISE

ANTICIPATOR

RISE

EM. HT.

LED (RED)

HEAT

CHECK

LED

(GREEN)

COOL

CHANGEOVER VALVE

FALL

HBTH

TDR 1

ANTICIPATOR

THERMOSTAT SUBBASE SYSTEM COMPONENTS

AUTO

COOL

TDR 2

HPA

COMPRESSOR

CONTACTOR

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

191 60-2485—8

Fig. 195. Schematic and hookup of T874G with Q674F. Used in heat pump applications.

Fig. 196. Schematic and hookup of T874G with Q674J. Used in heat pump applications.

FALL

FAN RELAY

COOL

CHANGEOVER

VALVE

EM. HT.

OFF

AUTO

SYSTEM

SWITCH

H1 ANTICIPATOR

C1 ANTICIPATOR

AUTO

FAN SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED. M2974

EM. HT.

RELAY

COMPRESSOR

CONTACTOR

AUX. HT. RELAY

FALL

RISE

"B" RELAY

(HOT)

ANTICIPATOR

EM. HT. LED

(RED)

AUX.

HT. LED

(GREEN)

COOL

HEAT

THERMOSTAT SUBBASE SYSTEM COMPONENTS

COMPRESSOR

FAULT

FALL

FAN RELAY

COOL

CHANGEOVER

VALVE

OFF

SYSTEM

SWITCH

H1 ANTICIPATOR

C1 ANTICIPATOR

AUTO

FAN SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

M2975

COMPRESSOR

CONTACTOR

O.D.T.

FALL

RISE

(HOT)

ANTICIPATOR

SUPL. HT.

LED

(RED)

SUPL. HT.

H.C.R.1

H.C.R.2

H.C.R.3

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8192

Fig. 197. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

Fig. 198. Schematic and hookup of T874L with Q674E. Used in standard applications.

FALL

(HOT)

FAN RELAY

AUX. HEATER

RELAY

COMPRESSOR

MONITOR

OUTDOOR

THERMOSTAT

OUTDOOR

THERMISTOR

COOL

CHANGEOVER

VALVE

COMPRESSOR

RELAY

AUX. HT.

LED (GREEN)

EM. HT.

LED (RED)

FAN

SWITCH

AUTO

EM. HT.

HEAT

OFF

COOL

SYSTEM

SWITCH

FALL

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED.

FIELD REMOVABLE JUMPER.

M2970

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FALL

COMPRESSOR

CONTACTOR

HEAT

AUTO

COOL

SYSTEM

SWITCH

H1 ANTICIPATOR AUTO

FAN

SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

M2976

STAGE 2

HEAT RELAY

FALL

C2 ANTICIPATOR

RISE C1

STAGE 1 HEAT RELAY

(HOT)

ANTICIPATOR

FAN RELAY

OFF

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

193 60-2485—8

Fig. 199. Schematic and hookup of T874G with Q674F. Used in heat pump applications.

Fig. 200. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

FALL

FAN RELAY

W3 RELAY

EM. HT.

OFF

AUTO

SYSTEM

SWITCH

H1 ANTICIPATOR

C1 ANTICIPATOR

AUTO

FAN SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED. M2977

COMPRESSOR

CONTACTOR

AUX. HT. RELAY

FALL

RISE

(HOT)

ANTICIPATOR

CHECK

LED

(RED)

AUX. HT. LED

(GREEN)

COOL

HEAT

EM. HT. RELAY

COMPRESSOR

FAULT

HEAT CHANGEOVER

VALVE

COOL CHANGEOVER

RELAY

RISE

EM. HT.

LED (RED)

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FAN RELAY

EM. HT.

OFF

SYSTEM

SWITCH

AUTO

FAN SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M2978

COMPRESSOR

CONTACTOR

SERVICE

(HOT)

SERVICE

LED

(YELLOW)

EM. HT.

LED (RED)

COOL

HEAT

OUTDOOR

THERMOSTAT

SEQ 2

SEQ 1

HEAT CHANGEOVER

VALVE

H2 ANTICIPATOR

RISE

H1 C1

FALL

C1 ANTICIPATOR

H1 ANTICIPATOR

THERMOSTAT SUBBASE SYSTEM COMPONENTS

OUTDOOR

THERMOSTAT

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8194

Fig. 201. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

Fig. 202. Schematic and hookup of T874D with Q674G. Used in standard applications.

FAN RELAY

EM. HEAT

OFF

SYSTEM

SWITCH

AUTO

FAN SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M2979

COMPRESSOR

CONTACTOR

SERVICE

(HOT)

SERVICE

LED

(YELLOW)

EM. HT.

LED (RED)

COOL

HEAT

OUTDOOR

THERMOSTAT SEQ 2

SEQ 1

HEAT CHANGEOVER

VALVE

ANTICIPATOR

RISE

H1 C1

RISE

C1 ANTICIPATOR

H1 ANTICIPATOR

RESET

THERMOSTAT SUBBASE SYSTEM COMPONENTS

C815A

OUTDOOR

THERMISTOR

OUTDOOR

THERMOSTAT

FALL

FAN RELAY B

HEAT RELAY 1

AUTO

OFF

SYSTEM

SWITCH

H1 ANTICIPATOR

C1 ANTICIPATOR

FAN

SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED M2980

THERMOSTAT SUBBASE SYSTEM COMPONENTS

(HOT)

COMPRESSOR

CONTACTOR 2

COMPRESSOR

CONTACTOR 1

FALL

C2 ANTICIPATOR

RISE

HEAT RELAY 2

(HOT)

ANTICIPATOR

"T" RELAY

FAN RELAY O

SERVICE

LED (RED)

SERVICE

LED (RED)

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

195 60-2485—8

Fig. 203. Schematic and hookup of T874L with Q674C. Used in heat pump applications.

Fig. 204. Schematic and hookup of T874D with Q674F. Used in standard applications.

FALL

OFF

SYSTEM

SWITCH

C1 ANTICIPATOR

AUTO

FAN SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

M2981

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FALL

RISE C1

H1 ANTICIPATOR

COMP.

FAULT

(RED)

AUTO

COMPRESSOR

CONTACTOR

(HOT)

FAN RELAY

HEAT CHANGEOVER

VALVE

COMPRESSOR

FAULT

FALL

HEAT RELAY 1

HEAT

OFF

COOL

SYSTEM

SWITCH

H1 ANTICIPATOR

C1 ANTICIPATOR

AUTO

FAN

SWITCH

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

LED IS NOT LABELED. JUMPER W2 TO X FOR AUXILIARY HEAT INDICATION. JUMPER E TO X FOR

EMERGENCY HEAT INDICATION. CONNECT SYSTEM MONITOR TO X TO IDENTIFY WHEN SYSTEM

NEEDS TO BE CHECKED. M2982A

THERMOSTAT SUBBASE SYSTEM COMPONENTS

EM. HT. RELAY

COMPRESSOR

CONTACTOR 2

COMPRESSOR

CONTACTOR 1

FALL

C2 ANTICIPATOR

RISE

HEAT RELAY 2

(HOT)

LED

(RED)

ANTICIPATOR

AUTO

EM. HT.

FAN RELAY

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8196

Fig. 205. Schematic and hookup of T874H with Q674C. Used in heat pump applications.

Fig. 206. Schematic and hookup of T874J with Q674J. Used in heat pump applications.

FALL

OFF

AUTO

SYSTEM

SWITCH

H1 ANTICIPATOR

C1 ANTICIPATOR

AUTO

FAN SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

LEDS ON SOME MODELS.

M2983

THERMOSTAT SUBBASE SYSTEM COMPONENTS

RISE

LED

(RED)

FAN RELAY

COMPRESSOR

CONTACTOR

(HOT)

LED

(RED)

COOL CHANGEOVER

VALVE

FALL Y

FAN RELAY

COMPRESSOR

CONTACTOR

OFF

SYSTEM

SWITCH

H1 ANTICIPATOR

C1 ANTICIPATOR

AUTO

FAN SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED. M2984

THERMOSTAT SUBBASE SYSTEM COMPONENTS

COOL

CHANGEOVER

VALVE

O.D.T.

FALL

RISE CO

(HOT)

ANTICIPATOR

SUPL. HT.

LED (RED)

H.C.R.1

H.C.R.2

H.C.R.3

C1 CO

SUPL. HT.

RISE

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

197 60-2485—8

Fig. 207. Schematic and hookup of T874J with Q674L. Used in heat pump applications.

Fig. 208. Schematic and hookup of T874D with Q674D. Used in standard applications.

FALL Y

FAN RELAY

COMPRESSOR

CONTACTOR

OFF

COOL

SYSTEM

SWITCH

H1 ANTICIPATOR

C1 ANTICIPATOR

AUTO

FAN SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

M2985

THERMOSTAT SUBBASE SYSTEM COMPONENTS

COOL CHANGEOVER

VALVE

O.D.T.

FALL

RISE CO

(HOT)

ANTICIPATOR

SUPL. HT.

LED (RED)

H.C.R.1

H.C.R.2

H.C.R.3

C1 CO

SUPL. HT.

RISE

HEAT

FALL

HEAT RELAY 1

H1 ANTICIPATOR

C1 ANTICIPATOR 1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

RC-RH REMOVABLE JUMPER WHEN SPECIFIED. M2986

THERMOSTAT SUBBASE SYSTEM COMPONENTS

COMPRESSOR

CONTACTOR 2

COMPRESSOR

CONTACTOR 1

FALL

C2 ANTICIPATOR

RISE

HEAT RELAY 2

(HOT)

ANTICIPATOR

(HOT)

FAN

SWITCH

SYSTEM

SWITCH

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8198

Fig. 209. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

Fig. 210. Schematic and hookup of T874Y with Q674E. Used in heat pump applications.

EM. HEAT

OFF

SYSTEM

SWITCH

AUTO

FAN SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

AUX. HT.

LED

(GREEN)

EM. HT.

LED (RED)

COOL

HEAT

H2 ANTICIPATOR

RISE

H1 C1

FALL

H1/C1

ANTICIPATOR

EM. HT. RELAY

COOL

CHANGEOVER

VALVE

COMPRESSOR

CONTACTOR

’"B" RELAY

EM. HT.

RELAY

(HOT)

FAN RELAY

AUX. HT. RELAY

M2987

FALL G

HEAT

OFF

COOL

SYSTEM

SWITCH

H1 ANTICIPATOR

C1 ANTICIPATOR

AUTO

FAN

SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M2988

THERMOSTAT SUBBASE SYSTEM COMPONENTS

COMPRESSOR

CONTACTOR 2

COMPRESSOR

CONTACTOR 1

FALL

C2 ANTICIPATOR

RISE

(HOT)

FILTER

LED

(YELLOW)

ANTICIPATOR

AUTO

FAN RELAY

HCO

FALL

CCO

COOL

CHANGEOVER

VALVE

HEAT

CHANGEOVER

VALVE

RESET

LED

(RED)

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

199 60-2485—8

Fig. 211. Schematic and hookup of T874G with Q674F. Used in standard applications.

Fig. 212. Schematic and hookup of T874A with Q674E. Used in standard applications.

FALL

FAN RELAY

W1 RELAY

EM. HT.

OFF

AUTO

SYSTEM

SWITCH

H1 ANTICIPATOR

ANTICIPATOR

AUTO

FAN SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M2989

THERMOSTAT SUBBASE SYSTEM COMPONENTS

COMPRESSOR

FAULT

AUX. HT. RELAY

FALL

RISE C1

(HOT)

ANTICIPATOR

EM. HT.

LED (RED)

AUX. HT.

LED

(GREEN)

COOL

HEAT

COMPRESSOR

CONTACTOR

FALL

HEAT RELAY 1

H1 ANTICIPATOR

C1 ANTICIPATOR

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

RC -RH REMOVABLE JUMPER WHEN SPECIFIED. M2990

THERMOSTAT SUBBASE SYSTEM COMPONENTS

COMPRESSOR

CONTACTOR 2

COMPRESSOR

CONTACTOR 1

FALL

C2 ANTICIPATOR

RISE

HEAT RELAY 2

(HOT)

ANTICIPATOR

(HOT)

FAN RELAY

HEAT

AUTO

COOL

SYSTEM

SWITCH

AUTO

FAN

SWITCH

OFF

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8200

Fig. 213. Schematic and hookup of T874L with Q674C. Used in heat pump applications.

FALL

LCOMPRESSOR

CONTACTOR

RELAY 1

N.O. 2

HIGH

SYSTEM

SWITCH

H1 ANTICIPATOR

C1 ANTICIPATOR

AUTO

OFF

FAN

SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

M2991

THERMOSTAT SUBBASE SYSTEM COMPONENTS

COOL

CHANGEOVER

VALVE

FALL

RISE CO

(HOT)

H2 ANTICIPATOR

CHECK

LED (RED)

MED

COMPRESSOR

CONTACTOR

RELAY

RELAY N.C.

AUX. HT. RELAY

R1 RELAY N.C. 1

R1 RELAY

K1 RELAY

K2 RELAY

RELAY

N.O 1

FIELD

REMOVABLE

JUMPER

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

201 60-2485—8

Fig. 214. Schematic and hookup of T874A with Q674B. Used in standard applications.

COMPRESSOR

CONTACTOR

HIGH

SYSTEM

SWITCH

COOL

OFF

FAN

SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

M2992

THERMOSTAT SUBBASE SYSTEM COMPONENTS

COOL

CHANGEOVER

VALVE

(HOT)

CHECK

LED (RED)

MED

AUX. HT. RELAY

R1 RELAY

K1 RELAY

K2 RELAY

RELAY

N.O. 1

HEAT

COMPRESSOR

CONTACTOR

FALL

H1 ANTICIPATOR

C1 ANTICIPATOR

RISE

S1 RELAY N.C.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8202

Fig. 215. Schematic and hookup of T874L with Q674B. Used in heat pump applications.

FALL

LCOMPRESSOR

CONTACTOR

RELAY 1

N.O. 2

HIGH

SYSTEM

SWITCH

H1 ANTICIPATOR

C1 ANTICIPATOR

COOL

OFF

FAN

SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

M2993

THERMOSTAT SUBBASE SYSTEM COMPONENTS

COOL

CHANGEOVER

VALVE

FALL

RISE C1

(HOT)

H2 ANTICIPATOR

CHECK

LED (RED)

MED

COMPRESSOR

CONTACTOR

RELAY

RELAY N.C.

AUX. HT. RELAY

R1 RELAY N.C. 1

R1 RELAY

K1 RELAY

K2 RELAY

RELAY

N.O. 1

FIELD

REMOVABLE

JUMPER

HEAT

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

203 60-2485—8

Fig. 216. Schematic and hookup of T874G with Q674J. Used in heat pump applications.

Fig. 217. Schematic and hookup of T874N with Q674C. Used in heat pump applications.

FALL

RISE

C1 RISE

(HOT)

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

REMOVE JUMPER FOR INDEPENDENT CONTROL OF W1 AND E TERMINALS.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

ANTICIPATOR

H2 ANTICIPATOR

ANTICIPATOR

SYSTEM

SWITCH

FAN

SWITCH

AUTO

OFF

EM. HT.

AUTO

EM. HT.

RELAY

COOL CHANGEOVER

VALVE

COMPRESSOR

CONTACTOR

M1629

AUX. HT.

LED

(YELLOW)

CHECK

LED

(RED)

SYSTEM

LED

(GREEN)

HPS 4R

5R 4R

SEQ 1

SEQ 2

FAN RELAY

M5900

(HOT)

ODT

EHR

HEAT CHANGEOVER VALVE

EHR

COMPRESSOR

CONTACTOR

OPTIONAL

COMPRESSOR FAILURE

CHECK LED

(GREEN)

FAN SWITCH

AUTO

SYSTEM

SWITCH

OFF

AUTO

FALL

H1 ANTICIPATOR

ANTICIPATOR

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

RISE

C1 ANTICIPATOR

D. P.

HEAT

CONTACTOR #2

FAN RELAY

HEAT

CONTACTOR #3

HEAT CONTACTOR #1

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8204

Fig. 218. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

(HOT)

EM. HT.

LED (RED)

AUX. HT.

LED (GRN) AUX. HT.

RELAY

FAN RELAY

"B" RELAY

COOL CHANGEOVER

VALVE

EM. HT. RELAY

COMPRESSOR

CONTACTOR

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

H1/C1

ANTICIPATOR

FALL

AUX. HT.

RELAY

ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

TERMINAL LABELED C/X ON SOME MODELS.

W3 TERMINAL AVAILABLE ON SOME MODELS ONLY.

M3683A

AUTO

FAN

SWITCH

FALL

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

205 60-2485—8

Fig. 219. Schematic and hookup of T874C with Q674C. Used in standard applications.

M5901

(HOT)

L2 1

FAN RELAY

SERVICE

LED (RED)

FAN SWITCH

OFF

AUTO

SYSTEM

SWITCH

AUTO

FALL

FALL 2

ANTICIPATOR

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE.

H2 OFFSET 12oF FROM H1.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

COMPRESSOR CONTACTOR 1

RISE

MONENTARY

CIRCUIT

ANTICIPATOR

HEAT RELAY 1

HEAT RELAY 2

CONTROL MODULE

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8206

Fig. 220. Schematic and hookup of T874W with Q674C. Used in standard applications.

Fig. 221. Schematic and hookup of T874H with Q674C. Used in heat pump applications.

M5929

FALL

(HOT)

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FAN

SWITCH

SYSTEM

SWITCH

AUTO

OFF

AUTO

SERVICE

LED (RED)

COMPRESSOR CONTACTOR #2

HEAT RELAY #2

FAN RELAY

COMPRESSOR CONTACTOR #1

HEAT RELAY #3

ANTICIPATOR

C2 RISE

RISE

FALL

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE.

CONTROL MODULE

HEAT RELAY #1

MOMENTARY

CIRCUIT

FALL

H3 SYSTEM MONITOR

M5902

(HOT)

COOL CHANGEOVER

VALVE

FAN SWITCH

AUTO

SYSTEM

SWITCH

OFF

AUTO

FALL

H1 ANTICIPATOR

1POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

C1 RISE

C1 ANTICIPATOR

RISE

FAN RELAY

FILTER LED (RED)

SERVICE

LED (YELLOW)

COMPRESSOR

CONTACTOR

24 VAC

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

207 60-2485—8

Fig. 222. Schematic and hookup of T874B with Q674E. Used in standard applications.

Fig. 223. Schematic and hookup of T874S with Q674F. Used in heat pump applications.

M5920

(HOT)

FAN RELAY

COMPRESSOR

CONTACTOR 2

HEAT RELAY

MALFUNCTION

LED (RED)

LOW

SPEED

LED

(GREEN)

FAN SWITCH

AUTO

SYSTEM

SWITCH

HEAT

AUTO

COOL

RISE

FALL 2

H1 ANTICIPATOR

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

SUBBASE SYSTEM COMPONENTS

OFF

COMPRESSOR

CONTACTOR 1

RISE

ANTICIPATOR

HIGH SPEED

LED (YELLOW)

SYSTEM

MONITOR

THERMOSTAT

M5923

(HOT)

FAN RELAY

COMPRESSOR

CONTACTOR 2

EM.HT. RELAY

MALFUNCTION

LED (RED)

LOW SPEED

LED (GREEN)

SYSTEM

SWITCH

HEAT

AUTO

COOL

RISE

H1 FALL

ANTICIPATOR

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

OFF

COMPRESSOR

CONTACTOR 1

RISE

ANTICIPATOR

HIGH SPEED

LED (YELLOW)

OCOOL

CHANGEOVER VALVE

AUX. HT. RELAY

AUX. HT.

LED (RED)

RISE

EM. HT.

FAN SWITCH

AUTO

FALL

H2 ANTICIPATOR

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8208

Fig. 224. Schematic and hookup of T874A,D with Q674E. Used in standard applications.

M5927

FALL

(HOT)

L2 1

(HOT)

L2 1

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FAN

SWITCH

SYSTEM

SWITCH

AUTO

OFF

HEAT

AUTO

COOL

SERVICE

LED (RED)

COOL CHANGEOVER VALVE

COMPRESSOR CONTACTOR #2

HEAT RELAY #2

FAN RELAY

COMPRESSOR CONTACTOR #1

HEAT CHANGEOVER VALVE

HEAT RELAY #1

ANTICIPATOR

C2 RISE

RISE

FALL

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

CONTROL MODULE

SYSTEM MONITOR

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

209 60-2485—8

Fig. 225. Schematic and hookup of T874D with Q674C. Used in standard applications.

M5928

FALL

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FAN

SWITCH

SYSTEM

SWITCH

AUTO

OFF

AUTO

SERVICE

LED (RED)

COOL DAMPER

COMPRESSOR CONTACTOR #2

HEAT RELAY #2

FAN RELAY

COMPRESSOR CONTACTOR #1

HEAT DAMPER

HEAT RELAY #1

ANTICIPATOR

C2 RISE

RISE

FALL

CONTROL MODULE

RH L1

(HOT)

L2 1

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

SYSTEM MONTIOR

(HOT)

L2 1

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8210

Fig. 226. Schematic and hookup of T874G with Q674G. Used in standard applications.

M5930

FALL

(HOT)

L2 1

(HOT)

THERMOSTAT SUBBASE SYSTEM COMPONENTS

SYSTEM

SWITCH

OFF

AUTO

SERVICE

LED (RED)

FAN RELAY O

COMPRESSOR CONTACTOR #2

HEAT RELAY #2

T RELAY

COMPRESSOR CONTACTOR #1

FAN RELAY B

HEAT RELAY #1

ANTICIPATOR

RISE

FALL

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

CONTROL MODULE

SERVICE

LED (RED)

NO FAN

SWITCH

SYSTEM MONITOR

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

211 60-2485—8

Fig. 227. Schematic and hookup of T874G with Q674F. Used in heat pump applications.

(HEAT)

FALL

RISE

FALL

(HOT)

RISE

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

W1 - Y1 JUMPER IS Y TERMINAL; REMOVE JUMPER WHEN W1 RELAY IS USED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

M1230B

W3 RELAY

FAN RELAY

AUX. HT.

RELAY

EM. HT.

RELAY

COMPRESSOR

FAULT

CHECK

LED (RED)

AUX.

HT. LED

(GREEN)

EM. HT.

LED (RED)

SYSTEM

SWITCH

OFF

EM. HT.

HEAT

AUTO

COOL COOL CHANGEOVER

RELAY

HEAT CHANGEOVER

RELAY

W1 RELAY

COMPRESSOR

CONTACTOR

ANTICIPATOR

(COOL)

H2 ANTICIPATOR

ANTICIPATOR

FAN

SWITCH

AUTO

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8212

Fig. 228. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

H1 FALL

(HOT)

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

REMOVABLE JUMPER (INSTALLED).

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H2 FALL

H1/C1 ANTICIPATOR

H2 ANTICIPATOR

RESET

EM. HT.

HEAT

OFF

COOL

AUX. HT.

LED

(GREEN)

EM. HT.

LED (YELLOW)

C815A OUTDOOR

THERMISTOR

COOL CHANGEOVER

VALVE

ELECTRIC

HEAT RELAY

ELECTRIC

HEAT RELAY

EM. HT.

O.D.S.

SERVICE

EM. HT. RELAY

FAN RELAY

COMP. RELAY O.L. IN. STAT. HI. PRO.

AUTO

M3259

SENSOR

LED (RED)

SYSTEM

SWITCH

FAN

SWITCH

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

213 60-2485—8

Fig. 229. Schematic and hookup of T874G with Q674F. Used in heat pump applications.

Fig. 230. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

H1 FALL

H2 FALL

RISE

(HOT)

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

REMOVABLE JUMPER (INSTALLED).

THERMOSTAT SUBBASE SYSTEM COMPONENTS

O.D.S.

H1 ANTICIPATOR

H2 ANTICIPATOR

C1 ANTICIPATOR

SYSTEM

SWITCH

FAN

SWITCH

AUTO

EM. HT.

OFF

HEAT

AUTO

COOL

ELECTRIC

HT. RELAY

ELECTRIC

HT. RELAY

M3264

EM. HT. RELAY

EM. HT.

LED (YELLOW)

RESET

COMP. RELAY O.L. IN. STAT. HI. PRO

FAN RELAY

SERVICE

C815A OUTDOOR

THERMISTOR

COOL CHANGEOVER

VALVE

AUX. HT.

LED

(GREEN)

SERVICE

LED (RED)

FALL

(HOT)

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

M5068

ANTICIPATOR

C ANTICIPATOR

ANTICIPATOR

FAN

SWITCH

AUTO

SYSTEM

SWITCH

EM .HT.

HEAT

OFF

COOL

AUX. HT.

LED

(GREEN)

EM. HT.

LED

(RED)

W3 RELAY

COOL

CHANGEOVER VALVE

COMPRESSOR

MONITOR

FAN RELAY

AUX. HT. RELAY

EM. HT. RELAY

HEAT

CHANGEOVER VALVE

COMPRESSOR

RELAY

CHECK

LED (RED)

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8214

Fig. 231. Schematic and hookup of T874G with Q674F. Used in heat pump applications.

Fig. 232. Schematic and hookup of T874D with Q674G. Used in standard applications.

C1 RISE

H2 FALL

FALL

RISE

(HOT)

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

ONLY TERMINAL B OR O TO BE USED. 0.8A MAX.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

SYSTEM

SWITCH

FAN

SWITCH

AUTO

OFF

EM. HT.

HEAT

AUTO

COOL

FAN RELAY

EM. HT. RELAY

AUX. HT. RELAY

COOL

CHANGEOVER

VALVE

HEAT CHANGEOVER

VALVE

COMPRESSOR

FAULT

ANTICIPATOR

H2 ANTICIPATOR

ANTICIPATOR

M5152

COMPRESSOR

RELAY

W3 RELAY

AUX. HT.

LED (GREEN)

EM. HT.

LED (RED)

(HOT)

SYSTEM

SWITCH

OFF

ANTICIPATOR

FALL

1POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED. M3957

RISE

ANTICIPATOR

RISE

AUTO

COMPRESSOR

CONTACTOR 2

FALL

HEAT RELAY 1

ANTICIPATOR

HEAT RELAY 2

COMPRESSOR

CONTACTOR 1

(HOT)

FAN RELAY

ANTICIPATOR

THERMOSTAT SUBBASE SYSTEM COMPONENTS

NO FAN

SWITCH

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

215 60-2485—8

Fig. 233. Schematic and hookup of T874W with Q674L. Used in heat pump applications.

Fig. 234. Schematic and hookup of T874G with Q674B. Used in heat pump applications.

FAN

SYSTEM

SWITCH

COOL

HEAT

ANTICIPATOR

FALL

M3952

AUTO

FAN

SWITCH

EM. HT.

LED (YELLOW)

SERVICE

LED (RED)

COMPRESSOR

LOW SPEED

FALL

AUX. HT.

COMPRESSOR

HIGH SPEED

EM. HT.

OFF

EM. HT.

W89

HEAT

PUMP

CONTROL

PANEL

COOL

CHANGEOVER

ANTICIPATOR

SERVICE LIGHT

EM. HT. LIGHT

OUTDOOR

RESET

FALL

ANTICIPATOR

RISE

RESET

THERMOSTAT SUBBASE SYSTEM COMPONENTS

RISE

OFF

ANTICIPATOR

FALL

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M3961

RISE

ANTICIPATOR

RISE

HEAT

FALL

AUX. HT. RELAY

COMPRESSOR

CONTACTOR

(HOT)

FAN RELAY

AUTO

FAN

SWITCH

AUX. HEAT

LED (RED)

ANTICIPATOR

COOL

CHANGEOVER

VALVE

COOL

THERMOSTAT SUBBASE SYSTEM COMPONENTS

SYSTEM

SWITCH

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8216

Fig. 235. Schematic and hookup of T874G and Q674F. Used in heat pump applications.

Fig. 236. Schematic and hookup of T874A-D with Q674C. Used in standard applications.

FALL

(HOT)

L2 1

RTD1 OTD1

EHR1

ODT2

EHR2

RTD2

RTD3

RTD1

SYSTEM

MONITOR

FAN

RELAY

COOL

CHANGEOVER VALVE

EM. HT.

RELAY

LACO

COMPRESSOR

CONTACTOR CHP

H1 FALL

H1 ANTICIPATOR

ANTICIPATOR

CHANGEOVER

RISE

ANTICIPATOR

OFF

COOL

AUTO

HEAT

EM. HT.

SYSTEM

SWITCH

AUTO

FAN

SWITCH

AUX. HT.

LED (GRN)

EM. HT.

LED (RED)

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

1M7064

THERMOSTAT SUBBASE SYSTEM COMPONENTS

M7570

THERMOSTAT SUBBASE SYSTEM COMPONENTS

H1 ANTICIPATOR

H2 ANTICIPATOR

RISE

H1 FALL

FALL

RISE

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

AUTO

FAN

SWITCH

SYSTEM

SWITCH

OFF

HEAT DAMPER

HEAT RELAY 1

COMPRESSOR

RELAY 1

HEAT RELAY 2

COMPRESSOR

RELAY 2

AUTO

SERVICE

LED (RED)

COOL DAMPER

FAN RELAY

CONTROL MODULE

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

217 60-2485—8

Fig. 237. Schematic and hookup of T874C with Q674B. Used in standard applications.

Fig. 238. Schematic and hookup of T874C with Q674F. Used in heat pump applications.

FALL G

FAN RELAY

OFF

COOL

SYSTEM

SWITCH

H2 ANTICIPATOR

H1 ANTICIPATOR

C1 ANTICIPATOR

AUTO

FAN SWITCH

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M7716

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FALL

RISE

(HOT)

COMPRESSOR

CONTACTOR

HEAT 1

HEAT 2

HEAT

LOW LED

(YELLOW)

HI LED

(GREEN)

FALL

(HOT)

L2 1

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

FACTORY INSTALLED JUMPER BETWEEN TERMINALS W1 AND Y1.

ANTICIPATOR FAN SWITCH

AUTO

SYSTEM

SWITCH

OFF

COOL

CHANGEOVER

VALVE

FAN RELAY

AUX. HT.

RELAY

HEAT PUMP

RELAY

M7719

ANTICIPATOR

B RELAY

THERMOSTAT SUBBASE SYSTEM COMPONENTS

COMPRESSOR

CONTACTOR

AUX. HT.

LED (RED)

RISE

FALL

ANTICIPATOR

2 STAGE HT.

HT. PUMP

AUX. HT.

CHECK

LED (RED)

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8218

Fig. 239. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

Fig. 240. Schematic and hookup of T874A with Q674W. Used in standard applications.

(HOT)

L2 1

POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

FAN SWITCH

AUTO

SYSTEM

SWITCH

HEAT

OFF

COOL

M7744

THERMOSTAT SUBBASE SYSTEM COMPONENTS

EM. HT.

FALL

ANTICIPATOR

RESET

FAN RELAY

AUX. HT.

RELAY

OUTDOOR

THERMOSTAT

COOL

CHANGEOVER

VALVE

COMPRESSOR

CONTACTOR

OUTDOOR

SENSOR

COMPRESSOR

MONITOR

AUX. HT.

LED (GREEN)

EM. HT.

LED (RED)

FIELD REMOVABLE JUMPER.

(HOT)

L2 1

POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

FAN CONTINUOUS IN ON POSITION.

SYSTEM

OFF

FAN

MED

M7745

THERMOSTAT SUBBASE SYSTEM COMPONENTS

FALL

RISE

ANTICIPATOR

ANTICIPATOR HEAT

RELAY

K1 RELAY

K2 RELAY

COMPRESSOR

CONTACTOR

B RELAY L2 L1

K1 K1

K2 K2 K2

3 SPEED FAN SCHEMATIC

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

219 60-2485—8

Fig. 241. Schematic and hookup of T874J with Q674L. Used in heat pump applications.

Fig. 242. Schematic and hookup of T874G with Q674C. Used in standard applications.

RISE

(HOT)

L2 1

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

FAN SWITCH

AUTO

SYSTEM

SWITCH

HEAT

OFF

COOL

FAN RELAY

HEAT

CHANGEOVER

VALVE NO. 1

HEAT

CHANGEOVER

VALVE NO. 1

HEAT

CHANGEOVER

VALVE NO. 2

HEAT

CHANGEOVER

VALVE NO. 2

HEAT

CHANGEOVER

VALVE NO. 3

M7742

THERMOSTAT SUBBASE SYSTEM COMPONENTS

COOL CHANGEOVER

VALVE

SUPL. HT.

FALL

RISE

COMPRESSOR

CONTACTOR

P RELAY

X RELAY

O.D.T.

SUPL. HEAT

LED (RED)

ANTICIPATOR

(HOT)

L2 1

H2 ANTICIPATOR

H1 ANTICIPATOR

C1 ANTICIPATOR

FALL

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

OVERRIDE IS MOMENTARY POSITION. SPRING RETURN TO (OFF)

UPON SWITCH RELEASE.

AUTO

FAN

SWITCH

SYSTEM

SWITCH

AUTO

OVERRIDE

OFF

RISE

FALL

RISE

HEAT DAMPER

HEAT RELAY 1

FAN RELAY

HEAT RELAY 2

OVERRIDE

CIRCUIT

OVERRIDE

CIRCUIT

CHANGEOVER

VALVE

COMPRESSOR

RELAY

SERVICE

LED (RED)

ON LED (YEL)

M7212

THERMOSTAT SUBBASE SYSTEM COMPONENTS

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8220

Fig. 243. Schematic and hookup of T874G with Q674F. Used in heat pump applications.

Fig. 244. Schematic and hookup of T874J with Q674J. Used in heat pump applications.

FALL

RISE

(HOT)

RISE 1

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED.

TERMINAL LABELED C/X ON SOME MODELS.

C1 ANTICIPATOR

H1 ANTICIPATOR FAN SWITCH

AUTO

SYSTEM

SWITCH

AUTO

HEAT

OFF

COOL

AUX. HEAT RELAY

FAN RELAY

EM. HT. RELAY

B RELAY

M7715

THERMOSTAT SUBBASE SYSTEM COMPONENTS

COMPRESSOR

CONTACTOR

EM. HT.

LED (RED)

AUX. HEAT

LED (GREEN)

COOL CHANGEOVER

VALVE

FALL

ANTICIPATOR

RISE

(HOT)

L2 1

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

FAN SWITCH

AUTO

SYSTEM

SWITCH

OFF

FAN RELAY

HEAT

CHANGEOVER

VALVE NO. 1

HEAT

CHANGEOVER

VALVE NO. 1

HEAT

CHANGEOVER

VALVE NO. 2

HEAT

CHANGEOVER

VALVE NO. 2

HEAT

CHANGEOVER

VALVE NO. 3

M7743

THERMOSTAT SUBBASE SYSTEM COMPONENTS

COOL CHANGEOVER

VALVE

SUPL. HT.

FALL

RISE

COMPRESSOR

CONTACTOR

P RELAY

X RELAY

O.D.T.

SUPL. HEAT

LED (RED)

ANTICIPATOR

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

221 60-2485—8

Fig. 245. Schematic and hookup of T874R with Q674L. Used in heat pump applications.

Fig. 246. Schematic and hookup of T874C with Q674G. Used in standard applications.

FALL

(HOT)

POWER SUPPLY. PROVIDE DISCONNECT

MEANS AND OVERLOAD PROTECTION

AS REQUIRED.

TERMINAL LABELED C/X ON SOME MODELS.

H1/C1

ANTICIPATOR FAN SWITCH

AUTO

SYSTEM

SWITCH

HEAT

OFF

COOL

AUX. HT. RELAY

FAN RELAY

EM. HT. RELAY

B RELAY

M7718

THERMOSTAT SUBBASE SYSTEM COMPONENTS

COMPRESSOR

CONTACTOR

EM. HT.

LED (RED)

AUX. HT.

LED (GREEN)

COOL CHANGEOVER

VALVE

FALL

ANTICIPATOR

HEAT RELAY 1

OFF

AUTO

SYSTEM

SWITCH

1M7717

THERMOSTAT SUBBASE SYSTEM COMPONENTS

(HOT)

HEAT RELAY 2

COOL CHANGEOVER

VALVE

(HOT)

H1 ANTICIPATOR

H2 ANTICIPATOR

C1 RISE

H1 FALL

FALL

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

NO FAN

SWITCH

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

60-2485—8222

Fig. 247. Schematic and hookup of T874W with Q674L. Used in heat pump applications.

C815A OUTDOOR

THERMISTOR

AUX. HT. RELAY

FAN RELAY

EM. HT. RELAY

CHANGEOVER

RELAY (HEAT)

CHANGEOVER

RELAY (COOL)

COMPRESSOR

CONTACTOR 1

COMPRESSOR

CONTACTOR 2

EM.HT.

AUTO

FAN SWITCH

H1 ANTICIPATOR

H2 ANTICIPATOR

H3 ANTICIPATOR

RESET

FALL

AUX. HEAT

LED (GREEN)

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

CONNECT CHANGEOVER RELAY TO 'O' TERMINAL FOR CHANGEOVER IN COOLING OR TO 'B' TERMINAL FOR CHANGEOVER IN HEATING. M6999

C1 ANTICIPATOR

RISE

RISE C2 ANTICIPATOR

EM. HEAT

LED (RED)

CHECK LED

(YELLOW)

HEAT

OFF

COOL

SYSTEM

SWITCH

THERMOSTAT SUBBASE SYSTEM COMPONENTS

(HOT)

L2 1

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

223 60-2485—8

Fig. 248. Schematic and hookup of T874Y with Q674F. Used in heat pump applications.

M5923

(HOT)

FAN RELAY

COMPRESSOR

CONTACTOR 2

EM.HT. RELAY

MALFUNCTION

LED (RED)

LOW SPEED

LED (GREEN)

SYSTEM

SWITCH

HEAT

AUTO

COOL

RISE

H1 FALL

ANTICIPATOR

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

THERMOSTAT SUBBASE SYSTEM COMPONENTS

OFF

COMPRESSOR

CONTACTOR 1

RISE

ANTICIPATOR

HIGH SPEED

LED (YELLOW)

OCOOL

CHANGEOVER VALVE

AUX. HT. RELAY

AUX. HT.

LED (RED)

RISE

EM. HT.

FAN SWITCH

AUTO

FALL

H2 ANTICIPATOR

60-2485—8 J.H. Rev. 3-01 www.hone

well.com

Home and Building Control Home and Building Control

Honeywell Honeywell Limited-Honeywell Limitée

1985 Douglas Drive North 35 Dynamic Drive

Golden Valley, MN 55422 Scarborough, Ontario

M1V 4Z9

Printed in U.S.A. on recycled

paper containing at least 10%

post-consumer paper fibers.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Fig. 249. Schematic and hookup of T874C with Q674B. Used in heat pump applications.

RISE

(HOT)

L2 1

RISE

FALL

M18622

H1 ANTICIPATOR

H2 ANTICIPATOR

C1 ANTICIPATOR

C2 ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

FIELD WIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER.

11 Y2

SYSTEM

SWITCH

HEAT

OFF

COOL

AUTO

FAN

SWITCH

HEAT RELAY 1

FAN RELAY

HEAT RELAY 2

HEAT DAMPER

COOL DAMPER

COMPRESSOR CONTACTOR 1

COMPRESSOR CONTACTOR 2

THERMOSTAT SUBBASE SYSTEM COMPONENTS

SERVICE

LED (RED)

Bryant Thermostat Q674 Users Manual 60 2485 T874 Multistage Thermostats And Subbases

T874 to the manual ad722da2-d369-4efc-b7c2-1152a01c2f4c

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