Honeywell Trol A Temp Q674B Users Manual 69 0580 T874A,D Zone Thermostats/Q674B,D,E Subbases

TROL-A-TEMP T874A 69-0580

T874A to the manual db3f0361-6f4b-4bb0-a045-8d1dc520f8be

2015-01-23

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T874A,D Zone Thermostats/
Q674B,D,E Subbases
Installation Instructions for the Trained Service Technician.

Application

See Table 1 for thermostat/subbase and system compatibility; see Table 2 for thermostat specifications. For complete
Honeywell Trol-A-Temp System specification and application information, refer to the system specification included with the control panel.

These T874A,D Zone Thermostats and Q674B,D,E
Subbases provide 24 to 30 Vac temperature control in
Honeywell Trol-A-Temp heating/cooling zone systems.

TABLE 1—THERMOSTAT/SUBBASE AND SYSTEM COMPATIBILITY.
Thermostat/
Subbase Model
Numbera
Mini-Zone
T874A/Q674B Zone 1; conventional
heat-cool.
T874A/Q674D Zones other than zone 1;
conventional heat-cool.
T874A/Q674E Not applicable
T874D/Q674B Not applicable
T874D/Q674D Not applicable
T874D/Q674E Not applicable
a

Application
Mabs II, Mabs II-L
Zone 1; conventional
heat-cool.
Zones other than zone 1;
conventional heat-cool.
Not applicable
Zone 1; conventional
heat-cool.
Zones other than zone 1;
conventional heat-cool
and heat pump.
Not applicable

Mabs XX
Stages
Any zone; conventional heat-cool. Single-stage
Not applicable

Single-stage

Any zone; conventional heat-cool. Single-stage
Any zone; conventional heat-cool. Multistage
Not applicable

Multistage

Any zone; conventional heat-cool. Multistage

Subbase not included with thermostat; order separately.
TABLE 2—THERMOSTAT/SUBBASE SPECIFICATIONS.
Thermostat/Subbase
Order Numbera
T874A1465/Q674B1471
T874A1465/Q674D1123
T874A1465/Q674E1379
T874D1801/Q674B1463
T874D1827/Q674B1471
T874D1801/Q674D1115
T874D1827/Q674D1123
T874D1827/Q674E1379

Switching
System
HEAT-OFF-COOL
None
HEAT-OFF-COOL-AUTO
HEAT-OFF-COOL
HEAT-OFF-COOL
None
None
HEAT-OFF-COOL-AUTO

Fan
ON-AUTO
None
ON-AUTO
ON-AUTO
ON-AUTO
None
None
ON-AUTO

Thermostat/
Subbase
Color
White/Gray
White/Gray
White/Gray
Beige/Brown
White/Gray
Beige/Brown
White/Gray
White/Gray

Anticipator Range (A)
Heating
Cooling
(Adj.)
(Fixed)
Stg. 1—
Stg. 1—
0.1 to 1.2
0 to 1.5
Stg. 1—
0.1 to 1.2;
Stg. 2—
0.1 to 1.0.

Stg. 1—
0 to 1.2;
Stg. 2—
0 to 1.0.

Subbase not included with thermostat; order separately.

Operation
On a 2-heat thermostat, the two stages of heat make
sequentially as the temperature drops. Make refers to the
mercury switch initiating a call for heat or cool.
There are about 2° F [1° C] between stages so that the
second stage makes only when the first stage cannot
handle the load. This is the interstage differential.

S. M. • Rev. 6-93 •

M3375

Recycling Notice

This control contains mercury in a sealed tube. Do not
place control in the trash at the end of its useful life.
If this control is replacing a control that contains mercury
in a sealed tube, do not place your old control in the trash.
Contact your local waste management authority for
instructions regarding recycling and the proper disposal of
this control, or of an old control containing mercury in a
sealed tube.
If you have questions, call Honeywell at 1-800-468-1502.

M3375

• ©Honeywell Inc. 1993 • Form Number 69-0580—2

Installation

Fig. 1—Installation of subbase on outlet box.

WHEN INSTALLING THIS PRODUCT…
1. Read these instructions carefully. Failure to follow them could damage the product or cause a hazardous condition.
2. Check the ratings given in the instructions and on
the product to make sure the product is suitable for your
application.
3. Installer must be a trained, experienced service
technician.
4. After installation is complete, check out product
operation as provided in these instructions.

HORIZONTAL
OUTLET
1
BOX
SUBBASE
1

NOT INCLUDED WITH UNIT.

M3703

Fig. 2—Installation of subbase on wall.

CAUTION
1. Disconnect power supply to prevent electrical
shock or equipment damage.
2. To prevent interference with the thermostat
linkage, keep wire length to a minimum and
run wires as close as possible to the subbase.
3. Do not overtighten thermostat captive mounting screws, because damage to subbase threads
can result.
4. Do not short across terminals of systems controls. This can burn out the thermostat heat
anticipator.

WALL

WIRES THROUGH
WALL OPENING

WALL
ANCHORS
(2)

IMPORTANT: Thermostats are calibrated at the factory by
using subbases mounted at true level. Inaccurate subbase leveling will cause thermostat control deviation.

M926

MOUNTING
HOLES

SUBBASE

MOUNTING
SCREWS (2)

Fig. 3—Subbase components and leveling
procedure.

LOCATION
Locate the subbase about 5 ft [1.5 m] above the floor in
an area with good air circulation at average temperature.
Do not mount the subbase where the thermostat may be
affected by:
— drafts or dead spots behind doors and in corners.
— hot or cold air from ducts.
— radiant heat from sun, appliances or fireplace.
— concealed pipes and chimneys.
— unheated (uncooled) areas such as an outside wall
behind the thermostat.

SPIRIT LEVEL

MOUNTING THE SUBBASE
The thermostat subbase can be mounted on a horizontal
outlet box or directly on the wall.
1. To mount on a horizontal outlet box, install the subbase on the outlet box as shown in Fig. 1.
For a wall installation, hold the subbase in position and
mark holes for the anchors (Fig. 2). Obtain wall anchors
locally. Take care that the wires do not fall back into the
wall opening. Set aside subbase. Drill two 3/16 in. [4.8 mm]
holes and gently tap anchors into the holes until flush with the
wall.
2. Pull electrical wires through the cover plate (if used)
and subbase cable opening (Fig. 3). See Wiring the Subbase section before pulling any wires.

MOUNTING
HOLES (2)

TOP
MOUNTING
HOLES (2)

WIRING
TERMINAL

POST (2) FOR
MOUNTING
THERMOSTAT

THERMOSTAT
CABLE OPENING

TO SPRING FINGER
CONTACTS ON THE
THERMOSTAT
(UP TO 12)
M927

4. Level the subbase using a spirit level, as shown in
Fig. 3, and firmly tighten the subbase mounting screws.
The subbase mounting holes allow minor out-of-level
adjustments.
IMPORTANT: An incorrectly leveled subbase will cause
the temperature control to deviate from set point.
WIRING THE SUBBASE
All wiring must comply with local electrical codes and
ordinances. Follow equipment manufacturer wiring instructions when available. To wire subbase:
1. Connect wires to the subbase terminals. Refer to
Figs. 6-10 for wiring diagrams of typical zone systems. A

IMPORTANT: Use 18 gauge, color-coded thermostat
cable for proper wiring.
3. Secure the subbase with the screws provided. Do not
fully tighten the subbase screws.

letter code is located near each subbase terminal for identification. The terminal barrier permits straight or conventional wraparound wiring connection (Fig. 4).
2. Some Q674 Subbases have RC and RH terminals
for isolated heating and cooling transformers. For zoning
systems, jumper RC and RH terminals as shown in Fig. 5
and wire as single R terminal.
3. Firmly tighten each terminal screw.
4. Fit wires as close as possible to the subbase. Push
excess wire back into hole.
5. Plug the hole with nonflammable insulation to prevent drafts from affecting the thermostat.

Fig. 5—Jumper RC and RH terminals for single
transformer system. Strip wire 3/4 in. [19 mm].

Fig. 4—Wiring connections.
FOR STRAIGHT
INSERTION–
STRIP 5/16 in. [8 mm]

FOR WRAPAROUND–
STRIP 7/16 in. [11 mm]

BARRIER
SUBBASE TERMINAL SCREW

M928

M929

Fig. 6—Typical hookup for MM-2 Mini-zone Control Panel with T874A Thermostat/Q674B,D Subbase in
single-stage heating-cooling two-zone system.
T874A THERMOSTAT/
Q674D SUBBASE

T874A THERMOSTAT/Q674B SUBBASE

Y1 RC

RH W1 W2

Y2 RC RH W2 W1

MINIZONE
(MM-2)
CONTROL
PANEL
HEAT
RELAY

COOL
RELAY

ZONE 1
RELAY

ZONE 2
RELAY

Y2
Y1
O
G2
TO SINGLESTAGE
HEATING/
COOLING
EQUIPMENT

CHANGEOVER
CONTROL

ZONE 1

ZONE 2

COOL

FAN

HEAT

24 V, 40 VA

TRANSFORMER

W2
W1
E

L2
1

DAMPER
ACTUATOR

L1
(HOT)

1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2 ZONE 1 O AND B TERMINALS MUST BE CONNECTED FOR PROPER SYSTEM OPERATION.
3 JUMPER RC AND RH TERMINALS TOGETHER AND WIRE AS SINGLE R TERMINAL.
4 DO NOT CONNECT W2 AND Y2 TERMINALS TO CONTROL PANEL.

M1633

69-0580—2

MOUNTING THE THERMOSTAT
1. Remove the thermostat cover by pulling the bottom
edge of the cover outward away from the base until it snaps
free from the cover clip.

spring fingers are not bent flat, preventing proper electrical contact with the subbase.
4. Set the heat anticipator indicator(s) to 0.1A for
proper system operation (Fig. 11).
5. Note the two tabs on the top inside edge of the
thermostat base. The tabs fit into the corresponding slots
on the top of the subbase. Mount the thermostat on the
subbase. See Fig. 12.
6. Align the two captive mounting screws in the thermostat base with the posts on the subbase (Fig. 12). Tighten
both screws. Do not overtighten the screws or damage to
the subbase posts can result.

NOTE: The cover is hinged at the top and is removed by
pulling out at the bottom.
2. Carefully remove and discard the polystyrene packing
insert that protects the mercury switches during shipment.
3. Turn over the thermostat base and note the spring
fingers that engage the subbase contacts. Make sure the

Fig. 7—Typical hookup for MABS II and MABS II-L Control Panels with T874A Thermostat/Q674B,D
Subbases in single-stage heating-cooling zone system. MABS II Control Panel shown; MABS II-L Control
Panel hookup is the same.

3
O

Y1 RC

4
RH

T874A THERMOSTAT/
Q674D SUBBASE

T874A THERMOSTAT/Q674B SUBBASE

4
Y1

W1 W2 Y2

Y2 RC RH

W2 W1

Y2 RC

RH W2

MABS II
CONTROL PANEL

EM. HEAT SECOND FAN
STAGE
RELAY
RELAY
RELAY

HEAT
RELAY

COOL
RELAY

Y
2
Y
1
O

TO SINGLESTAGE
HEATING/
COOLING
EQUIPMENT

G
2
G
1
R
C
R
H
B
W
2
W
1
E

CHANGEOVER
CONTROL
COOL
FAN
ADD-AZONE
A
HEAT
4
A
EM. HEAT
3
A
24 V, 40 VA
2
A
TRANSFORMER
1

O
1
G
1
B
1
E
1
2
1

CAC
RELAY

ZONE 1 ZONE 2
RELAY RELAY

ZONE 3
RELAY

ZONE 1

ZONE 2

ZONE 3

T
8
T
7
T
6
T
5
T
4
M
6
M
4
M
1

1
L2

DAMPER
ACTUATOR

L1
(HOT)
1

DAMPER
ACTUATOR
X

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

JUMPER RC, RH TOGETHER AND WIRE AS SINGLE R TERMINAL.

ZONE 1 O AND B TERMINALS MUST BE CONNECTED FOR PROPER SYSTEM OPERATION.

DO NOT CONNECT W2 AND Y2 TERMINALS TO CONTROL PANEL.

DAMPER
ACTUATOR
X

M1634

Fig. 8—Typical hookup for MABS II and MABS II-L Control Panels with T874D Thermostat/Q674B,D
Subbases in multistage heating-cooling zone system. MABS II Control Panel shown; MABS II-L Control
Panel hookup is the same.

2
RC

Y2 W2

T874D THERMOSTAT/
Q674D SUBBASE

T874D THERMOSTAT/Q674B SUBBASE

RC Y2

RH W1

4
W2

RC Y2

RH W1

4
W2

RH W1

MABS II
CONTROL PANEL

EM. HEAT SECOND FAN
STAGE
RELAY
RELAY
RELAY

HEAT
RELAY

COOL
RELAY

CAC
RELAY

ZONE 1 ZONE 2
RELAY RELAY

ZONE 3
RELAY

ZONE 1

ZONE 2

ZONE 3

CHANGEOVER
CONTROL

COOL

FAN

Y2
Y1

TO SINGLESTAGE
HEATING/
COOLING
EQUIPMENT

G1
RC
RH

ADD-A-ZONE

HEAT

EM. HEAT

24 V, 40 VA

TRANSFORMER

1
L2

DAMPER
ACTUATOR

L1
(HOT)

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

JUMPER RC, RH TOGETHER AND WIRE AS SINGLE R TERMINAL.

ZONE 1 O AND B TERMINALS MUST BE CONNECTED FOR PROPER SYSTEM OPERATION.

IF SINGLE-STAGE COOLING, DO NOT CONNECT Y2; IF SINGLE-STAGE HEATING, DO NOT CONNECT W2.

DAMPER
ACTUATOR
1

M1393A

69-0580—2

Fig. 9—Typical hookup for MABS XX Control Panel with T874A Thermostat/Q674B,E Subbases in singlestage heating-cooling zone system.

MABS XX
CONTROL PANEL
ZONE 1
FAN

HEAT

COOL

ZONE 2
FAN

HEAT

COOL

ZONE 3
FAN

HEAT

COOL

1
MCM
CAC

3
ZONE 2

FAN
ZONE

ZONE 3

FAN
SYS

ZONE

ADD-AZONE

ZONE 1

FAN
SYS

ZONE

SYS

4
5
6

DAMPER

TO SINGLESTAGE
HEATING/
COOLING
EQUIPMENT

DAMPER

7
8

RC RH

W M6 M4 M1 VO VC

OPEN

ZONE 1
1

CLOSE OPEN

OPEN

ZONE 3

ZONE 2
G

M6 M4 M1 VO VC

W M6 M4 M1 VO VC

1
L2
L1
(HOT)

W2
O

O
4

B
T874A
THERMOSTAT/
Q674B OR E
SUBBASE

4
B

DAMPER
ACTUATOR
X

DAMPER
ACTUATOR

T874A
THERMOSTAT/
Q674B OR E
SUBBASE

T874A
THERMOSTAT
Q674B OR E
SUBBASE

DAMPER
ACTUATOR
1

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

WIRE ONLY THE TERMINAL CONNECTIONS SHOWN. SOME TERMINALS NOT AVAILABLE ON ALL THERMOSTATS. IF THERMOSTAT HAS
R/RC/RH TERMINALS, JUMPER TOGETHER AND WIRE AS SINGLE R TERMINAL. DO NOT CONNECT THERMOSTAT O AND B TERMINALS
TO CONTROL PANEL.
M1636

Settings

Checkout
Before beginning checkout of thermostat operation,
set switches on the control panel for the desired system
operation. See instructions provided with the control panel.

Control
Panel
Mini-zone
MABS II
MABS II-L

MABS XX

To set up the system for thermostat checkout, adjust
each thermostat settings as shown in Table 5.

TABLE 5—SYSTEM SET-UP FOR THERMOSTAT CHECKOUT.
Heating
Cooling
Zones Other
Zones Other
Zone 1
Than Zone 1
Zone 1
Than Zone 1
Set thermostat
Move the heating set
Set thermostat
Move the cooling set
system switch to
point lever 10° F
system switch to
point lever 10° F
HEAT; set fan switch
[6° C] below room
COOL; set fan
[6° C] above room
to AUTO. Move the
temperature.
switch to AUTO.
temperature.
heating set point
Move the cooling
lever 10° F [6° C]
set point lever 10° F
below room
[6° C] above room
temperature.
temperature.
On all zone thermostats, set the system
On all zone thermostats, set the system
switch to HEAT; set the fan switch to AUTO.
switch to COOL; set the fan switch to AUTO.
Move the heating set point lever 10° F [6° C]
Move the cooling set point lever 10° F [6° C]
below room temperature.
above room temperature.
NOTE: The control panel provides a threeminute time delay when 24V is applied to
the control panel and at the end of each
equipment cycle. The high-speed fan runs
during this time delay.

HEATING

NOTE: The control panel provides a threeminute time delay when 24V is applied to
the control panel and at the end of each
equipment cycle. The high-speed fan runs
during this time delay.

COOLING

NOTE: If a plenum fan control is used in the heating
system, there will be a short delay on a call for heat to
allow the furnace to heat the plenum. The fan starts
immediately in electric heat systems. Allow 30 seconds
for the damper to open or close completely.
Make sure all zone thermostats are set as instructed in
the Heating column in Table 5. Check each zone thermostat as follows:
1. If thermostat has a fan switch, set it to ON. See
Fig. 13. After 30 seconds, place your hand in front of an
air register in that zone to check for air flow at the register.
2. Reset fan switch, if provided, to AUTO. After 30 seconds, make sure air flow at register has stopped.
3. Move heating set point lever on zone thermostat
10° F [6° C] above room temperature to call for heat.
4. After 30 seconds (longer, if necessary, for time delay
on plenum fan control), check for warm air at the register.
5. Move heating set point lever on the zone thermostat
10° F [6° C] below room temperature to end a call for heat.
After 30 seconds (longer, if necessary, for time delay on
plenum fan control or control panel), check that air flow at
the register has stopped.
6. Repeat steps 1-5 for each zone thermostat.

CAUTION
Do not operate cooling equipment if outdoor
temperature is below 50° F [10° C]. Refer to
manufacturer recommendations.

Make sure all zone thermostats are set as instructed in
the Cooling column in Table 5. Check each zone thermostat as follows:
1. Move cooling set point lever on the zone thermostat
10° F [6° C] below room temperature to call for cooling.
2. After 30 seconds, place your hand in front of an air
register in that zone to check for cool air at the register.
3. Move the cooling set point lever on the zone thermostat 10° F [6° C] above room temperature to end the call for
cooling. After 30 seconds (longer, if necessary, for time
delay on control panel), check that air flow at the register
has stopped.
4. Repeat steps 1-3 for each zone thermostat.
When system checkout is complete, return all thermostats to the desired settings for normal system operation.

69-0580—2

Calibration

Fig. 14—Thermometer calibration.

THERMOSTAT
T874 thermostats are accurately calibrated at the
factory. They do not have provision for field calibration.
THERMOMETER
The thermometer in your thermostat has been accurately calibrated at the factory. The thermometer should
only need adjustment if it has been dropped or shifted due
to mishandling.
If the set point lever and the thermometer reading do
not agree:
1. Remove the thermostat cover by pulling up from the
bottom of cover until it clears the mounting slots.
2. Set the thermostat cover on a table near an accurate
thermometer.
3. Allow ten minutes for the cover thermometer to
sense the area temperature; compare the readings. Be careful not to touch the thermometer or breathe on it.
4. If the readings are the same, replace the cover and put
the system into operation.
5. If the readings are different, insert a small screwdriver in the thermometer slot (Fig. 14) and turn it until the
thermometers have the same reading.
6. Replace the thermostat cover and put the system into
operation.

M5070

NOTE: Hand heat will offset the thermometer reading.
After making each adjustment, wait ten minutes for
the thermometer to stabilize before comparing.

Home and Building Control
Honeywell Inc.
1985 Douglas Drive North
Golden Valley, Minnesota 55422

Printed in U.S.A.

Home and Building Control
Honeywell Limited—Honeywell Limitée
740 Ellesmere Road
Scarborough, Ontario
M1P 2V9

Helping You Control Your World

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Honeywell Trol A Temp Q674B Users Manual 69 0580 T874A,D Zone Thermostats/Q674B,D,E Subbases

TROL-A-TEMP T874A 69-0580

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