LENNOX Controls And HVAC Accessories Manual L0806363

User Manual: LENNOX LENNOX Controls and HVAC Accessories Manual LENNOX Controls and HVAC Accessories Owner's Manual, LENNOX Controls and HVAC Accessories installation guides

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ZENNOX

t,_2004 Lennox industries Inc,

Dallas, Texas, USA

HEAT PUMP

KITS AND ACCESSORIES

_pu Technical

blications

Lithe U.S.A.

502,755M

09/2004

Supersedes 05/2003

FUELMASTER 21 ¢

CONTROL BOARD

INSTALLATION INSTRUCTIONS FOR FUELMASTER 21 ¢(FM21) CONTROL BOARD

Package 1 of 1 contains:

1 - FM21 board

1 - Mounting box with cover

1 - Bag assembly containing:

4 - #8 - 18 x 1/2" screws

The FM21 FueIMaster 21° control board is designed for

use with a conventional gas or oil furnace in combination

with a heat pump.Optional kits for service light (SLC1)

and defrost thermostat probe (DTR1) are available. An

outdoor thermostat may be used with the FM21 when

low temperature heat pump lockout is desired.

NOTE -A time delay relay (54G5701) is required when

an outdoor thermostat is used.

When the outdoor temperature is below the outdoor ther-

mostat setting, the time delay relay (DL10) will provide a

two-second delay before the compressor contactor is

energized. Refer to figure 3 for field wiring.

During a call for heat with the FM21, the heat pump will

provide first- stage heating. However, if first-stage op-

eration does not satisfy the heating demand, second-

stage heat is provided by the furnace as the secondary

source of heat. The FM21 automatically terminates heat

pump operation and starts the furnace.

The FM21 also controls the indoor blower speed. The in-

door blower runs in high speed during first-stage heating

(provided by the heat pump). When there is a need for

second-stage heating, the FM21 stops the blower, al-

lows the furnace heat exchanger to warm up, and then

operates the indoor blower on heating speed. In situa-

tions that require the blower to run continuously, the

blower speed will change automatically from heat pump

(high speed) to furnace (heating speed).

If the optional defrost thermostat probe, DTR1, is used,

the indoor blower will run continuously on high speed

during both first-stage and second-stage heating without

interruption.

1. Determine an appropriate indoor location close to

the furnace to install the FM21 control box. The box

may be installed on the furnace to facilitate wiring.

IMPORTANT

Use the provided screws to secure the control box.

Refer to figure 1 for dimensions.

NOTE -Standard 18-gauge thermostat wire is rec-

ommended for all wiring.

Remove the FM21 control box cover and make the

thermostat connections to the FM21 board, Termi-

nals for the thermostat connections are located on

the left side of the FM21 board,

Make furnace and heat pump connections to termi-

nals on the FM21 board, These terminals are lo-

cated on the right side of the FM21 board,

NOTE -If the furnace is equipped with a SureLighltb

ignition control board, a wire must be connected

from the heat pump Y1 terminal on the FM21 board

to the Y terminal on the furnace SureLight ignition

control board. This will ensure indoor blower opera-

tion on cooling speed during heat pump operation.

Run wires through the electrical inlets as shown in

figure 2.

If outdoor thermostat (S26) is being used with FM21,

remove jumper JR2 that is located on the upper left

side of the FM21 board. The jumper may be stored

by placing it on one pin only. Wire the outdoor ther-

mostat (S26) to the outdoor thermostat terminals on

the FM21 board. See figure 3 for wiring.

Page 1

7. If usingoptionalDTRI-1defrostthermostatboard,

removejumperJR1whichis locatedat theupper

rightsideoftheFM21board.Jumpermaybestored

byplacingitononepinonly.InstallDTRI-1boardas

outlinedintheinstallationinstructionshippedwith

thekit,

8. If usingoptionalSLC1servicelightcontrol,install

andadjustasoutlinedintheinstallationinstruction

shippedwiththekit,

Checktheoperationof the controlusingthe trouble-

shootingtablesandoperationdiagrams.

LENNOX FM21 DIMENSIONS

MOUNTING

HOLES (4)

DTR1

DEFROST KIT

(OPTIONAL)

FM21

CONTROL

BOARD

SLCl

SERVICE

LIGHT KIT

(OPTIONAL)

FRONT VIEW

2-5/8

(67)

3/16

(5)

5-1/4

(133)

2-5/8

(67)

10-1/2

(267)

1-7/8

_!-- (48)_"

SIDE VIEW

Figure 1

Page 2

ToOptionalOutdoor

Thermostat(3wires)

LENNOX FM21 WIRING INLETS

To Optional DTRI-1

Probe (2 wires)

To Furnace (5 wires)

MOUNTING

HOLES (4) _

DTR1

DEFROST KIT

(OPTIONAL)

Wire used only

if furnace is

/equipped with

SureLight ignition

control board

FM21

CONTROL

BOARD

SLCl SERVICE

LIGHT KIT

(OPTIONAL)

To Room

Thermostat (10

wires maximum) FRONT VIEW

Figure 2

To Heat Pump (8

wires maximum)

Page 3

"-O

(.Q

"11

(_" C

(- G

REMOVE JUMPER IF

OUTDOOR THERMOSTAT

IS USEO_

sz6 N

OUTDOOR

THERMOSTAT

(OPTIONAL)

WARM

COOL

" 24VAC COMMON

0INDOOR BLOWER

024VAC POWER

0 IST STAGE COOL/HEAT

(_ 2ND STAGE COOL '/_

0 AUXILIARY HEAT

0 REVERSING VALVE

0 AMBIENT SENSOR "/_

0EMERGENCY HEAT

SERVICE LIGHT ZZiX

ROOM

THERMOSTAT

DEFROST OPTION

SB9

DISCHARGE THERMOSTAT PROBE

OTl-i

DISCHARGE RELAY

BOARD

]

FIRRRRRRRRR

I r

LUUUUUUUUUUI

]

DTRI-I

A30

IWARM

2 COMMON

3 COOL

0 C

0 o

O R

0 Yi

0 YZ

0wl

0 o

0 T

SERVICE LIGHT

OPTION BOARD

0 _ w,

b_ o

A2g

5 z i A

0 _ JR5

DE -/ LWR

TYP TYP A31

FM21 Heat Pump Control

NOTE -

EXTERNAL 75VA,24V TRANSFORMER

(REQUIRED IF DEFROST OPTION IS USED)

TRANSFORMER MOUNTED IN ELECTRICAL BOX

DISCONNECT TRANSFORMER IN 7

FURNACE AND CONNECT NEW /

TRANSFORMER SECONDARY {24V) /

TO FURNACE WIRING /

/-.JUMPER MUST BE REMOVED /

/IF DEFROST OPTION /

/KIT IS USED /

FUR C

'VA° OI'C-&l II

Z4VACPOWER DIR I_l

BLOWER - I 75VA,24.V

INDOOR 91 G TRANSFORMER

Y2 DLIO

DEFROST DETECT @1 Z_ (2 SEC

REVERSING VALVE 0 DELAY)

24VAC COMMON L_R_,_

AMBIENT SENSOR Z_

24VAC POWER

SERVICE LIGHT

HEAT PUMP

LIST STAGE COOLIHEA_-_=Y,

2ND STAGE COOL _ (_)

Z_ NOT USED ON ALL UNITS

POSITION JUMPER (JR3) ON %2 (SHOWN) FOR

WHITE-RODGERS THERMOSTAT. IF GE OR

HONEYWELL THERMOSTAT USED, SWITCH JUMPER

(JR3) TO POSITION 2-3.

Y TO YI CONNECTION REQUIRED IN SURELIGHT

APPLICATIONS ONLY TO ENSURE INDOOR SLOWER

OPERATION ON COOLING SPEED DURING HEAT PUMP

OPERATION.

/2'_ DL10 NOT USED WHEN DTRI-1 IS INSTALLED.

AMBCOMPTHERM

[_ STG2COOL

24VPWR

[_]qAUXHEAT

COOL

o _ STG_COMP

;u OUTDOOR

T'STAT

0 (OPT)

REVVALVE

24V COM

[_ FAN

[_ EM HEAT

E_ SERV LIGHT

DISCHARGE

T'STAT

LOW VOLTAGE BOARD

FIELD WIRING (DEFROST

CONNECTIONS HT. OPT.

DTRI-1 )

FM21 SCHEMATIC DIAGRAM

FM21

q_J

12Kq r_

Y1 24V POWER _

8 q4 _

-4 1K-1 4Kq mO4_ DEFROST

COOL DEFR _ LED

MODE OST 0 :_ [_

REMOVE

JR2

JUMPER

WHEN

OUTDOOR

T'STAT IS O>

USED. m

D []

ICOOL 12K

MODE

2K_1

AUX HT

COM

Y1 OUT

K Y1 IN

8K-1

COMP FAN

S89

FURNACE

SUPPLY

D]SCHARGE

T'STAT

OPEN 90F

CLOSE 80F

6K 8K

DEF/COOL COMP

MODE FAN

_,MB COMP THERMISTER

STG 2 COOL

24V PWR

[]

-N

[] c

[] o

[]

STAT

SLC1 OPTIONAL

SERVICE LIGHT

BOARD

POSITION 1-2 SHOWN - USED

FOR WHITE-RODGERS ROOM

Z_ T'STAT. tF GE OR HONEYWELL

T'STAT IS USED, SWITCH

JUMPER TO POSITION 2-3.

$54 NOT STANDARD ON MERIT

z_ HEAT PUMPS. KITAVAILABLE.

Wiring Connections

This diagram represents the internals of the FM21.

Operating Sequence

The diagrams on the following pages show the sequence of events which take place during normal

operation. During most normal operation, an input received from the indoor thermostat will evoke a

response in the furnace or heat pump.

Page 5

ALTERNATE ROOM THERMOSTAT JUMPERS AND WiRiNG CONNECTIONS TO FM21 CONTROL

"-0

Z_ MOST UNUSED THERMOSTAT TERMINALS NOT SHOWN.

z_ CONNECTION USED ONLY WITH HEAT

SERVICE LIGHT

PUMPS EQUIPPED WITH $54 SERVICE LIGHT T'STAT.

$54 AVAILABLE IN MONITOR KIT #76F53.

Z_ JR 3 SET FOR "WR TYR", SERVICE LIGHT ENERGIZED

WHEN 24VAC IS APPLIED TO T'STAT TERMINAL L.

ELITE

THERMOSTAT

# 49M57

cc_

G O_

RO_

YI (_

Y2O_

Z_ EIW17( m,

43 w2"O

SIGNATURE

THERMOSTAT

# 51M28

cC)_--

G C)_--

RC)_--

Y/ O_--

Y20_--

w2'_ I

42)

-(3 L Q)@ --

HC_

DC_

OUTDOOR SENSOR, IF USED.

REQUIRES SEPARATE CABLE

FROM T'STAT TWISTED PAIR.

MIN. 22AWG, 300 FT. MAX.

Z_ THE FM21 OUTDOOR T'STAT & THE ROOM T'STAT

OUTDOOR SENSOR SHOULD NOT BOTH BE USED.

USE ONE OR THE OTHER. USE OF BOTH SENSORS

CREATES BALANCE POINT CONFLICT.

THE E INPUT OF THE FM21 IS USED ONLY WHEN A

Z_ DTRI _1 BOARD IS USED. THE E INPUT REQU IRES A

CONSTANT WRVAC INPUT DURING EMERGENCY HEAT MODE.

Z_ E,_Y1 OF THE THERMOSTAT IS THE 1ST STAGE OF

EMERGENCY HEA1L DO NOT CONNECT THE E INPUT

(OPTIONAL MANUAL SWITCH MAY BE WIRED FROM "R" TO "E")

W2 IS THE 1ST STAGE OF AUXIALARY HEAT JUMPER

z_ E,_YI TO W2.

$26

OUTDOOR

THERMOSTAT

z_(OPTIONAL)

DSL-450 #32M07

DSL-600 #13K97 L23 #91H73

24V _

RS20

RS+V

RS1

OUTDOOR SENSOR IF USED

REQUIRES SEPARATE 3-21RE

CABLE FROM T'STAT, 22AWG

MINIMUM, 300 FT. MAX.

T8611G 2101 TYPICAL ROOM

L22 #91H72 (2000 SERIES) THERMOSTAT

24VAC COMMON

INDOOR BLOWER

24VAC POWER

1ST STG COOL/HEAT

2ND STG COOL

AUXILIARY HEAT

REVERSING VALVE

AMBIENT SENSOR

EMERGENCY HEAT

SERVICE LIGHT

# 37L60

G _ G (_

R _ R ([_

(_ YI O

W1 YI Y20

w20 L w_ O

OlBC_ o O

T O

E CF_ E O

L_ L O

CHANGE T'STAT

FACTORY SETTING

INSTALLER SETUP

#29 FROM "0" TO "1"

TO ENERGIZE

REVERSING VALVE

O/B/TERMINAL IN

COOLING (sEE

T'STAT INSTALLATION

MANUAL).

TO HUMIDIFIER RELAY IF USED.

-- DEHUMIDIFICATION CONTROL, IF USED

CONNECT TO FURNACE DS ON VARIABLE

SPEED MODELS (REMOVE DS*R JUMPER).

THE ELITE & SIG. T'STATS AUTOMATICALLY TURN

ON THE BALANCE POINT FUNCTIONS WHEN THE

OUTDOOR SENSOR IS CONNECTED. THE ELITE &

SIG. T'STATS CANNOT READ THE OUTDOOR TEMP.

WITHOUT EMPLOYING THE BALANCE POINT

FUNCTION. IF DISPLAYING THE OUTDOOR TEMP. OR

USING OUTDOOR SENSOR FOR THE HUMIDITY

FUNCTION, THE FM21 $26 OUTDOOR THERMOSTAT

MUST NOT BE CONNECTED. (EUTE T'STAT DOES

NOT HAVE AN ADD HUMIDITY FUNCTION.)

DO NOT USE ELITE, SIG,, DSL T'STATS WITH FM21 WHEN

Z_ DEFROST HEAT OPTION MODULE tS USED ON FM21 (NO

EM, HT, 24V OUTPUT TERMINAL ON STAT).

O REMOVE JUMPER /

IsIFOUTDOORusEDSTAT/

OUTDOOR

THERMOSTAT

1 WARM 1

2COMMO

3 COOL

G60UHV/G61MPV WITH FM21, HPXA19 & SIGNATURE THERMOSTAT 51 M28

"-O

I THERMOSTAT MAY BE SET FOR DUAL FUEL

OR NORMAL HEAT PUMP OPERATION SEE

SEQUENCE OF OPERATION

OUTDOOR SENSOR REQUIRES SEPARATE

CABLE FROM T'STAT TWISTED PAIR. MIN.

22AWG 300 FT. MAX.

SIGNATURE

THERMOSTAT

CAT# 51 M28

DO NOT CONNECT "1'

DO NOT CONNECT "2'

DO NOT CONNECT "3'

THERMOSTAT

DO NOT CONNECT "E'

ODISCH. STAT

(DTI-1) 1

CLOSED WHEN 2

COOL

°000°000 000°0

PLUGS INTO THE /

FM21-I BOARD ] DTRI-1 REVA

O REMOVE JUMPER REMOVE JUMPER O

IFOUTDOOR STAT IFDTRI-1 BOARD

IS USED IS USED

OUTDOOR

THERMOSTAT FURNACE

1 WARM

2 COMMON

3 COOL

THERMOSTAT

® R

_) Y1

Q Wl

@ 0

® T

@ E

_ HEAT PUMP

O Y2

Q T

£Sb'H_Z

FM21 FUELMASTER O

$89

DISCHARGE

THERMOSTAT

I | PROBE

G60U HV/G61 MPV

_:D DS

@ Y1

_) C

__ R

_) Wl

HEAT PUMP

O Wl

4Do

©c

HPXA19,HP21

HPXA12,HPXB15

75VA, 24V

TRANSFORMER

OIL FURNACE WITH FM21, HEAT PUMP AND HEAT PUMP THERMOSTAT

DISCHARGE

THERMOSTAT

PROBE

NOTE - IF OPTIONAL

OUTDOOR TEMR

SENSOR tS USED,

DO NOT USE 56A87

OUTDOOR T'STAT.

56A87

OUTDOOR

THERMOSTAT

(OPTIONAL)

G O

R O

Y O

E©

HEAT PUMP

THERMOSTAT

ODISCH. STAT

(DT1-1) 1

CLOSED WHEN 2

COOL

00o 000o 000_

PLUGS INTOTHE F

FM2%1 BOARD

@REMOVE JUMPER

IF OUTDOOR STAT

IS USED

OUTDOOR

THERMOSTAT

WARM

COMMON

COOL

000°0

I.ENNDXO

DTRI-1 REVA

THERMOSTAT

@ E

REMOVE JUMPER O

IF DTR%l BOARD

IS USED

FURNACE

_ w

HEAT PUMP

0000

0000 000

I_ENNDX

FM21-1 REVA

16J92 FM21

HEAT PUMP CONTROL

16J93

DEFROST

CONTROL

NOTE:

EXTERNAL 75VA, 24V TRANSFORMER

REQUIRED,

MOUNTED IN ELECTRICAL BOX

75VA, 24V

TRANSFORMER

JHEAT PUMP

@ Y1

_} wl

©o

©c

_) R

h48G95

RELAY

48G95

RELAY

OIL FURNACE

WITH HONEYWELL

ST9103A CONTROL

FM21 COOLING SEQUENCE -WITHOUT DEFROST OPTION

ii!!i_ii!_ iiliiiitj_

i!_ _¸ _b_

YI _'-- IST STAGE COOL/HEAT _YI

ooo

Operating Sequence -Cooling:

The diagram above shows the input and output signals in the

FM21. The following operating sequence steps through the in-

puts (left side of diagram) and the resulting outputs (right side

of diagram).

CONDITION:

With or Without Outdoor Thermostat

Constant Fan -Fan Switch "ON"

Blower (G) -Thin Black Line

1 - Blower demand from the thermostat passes directly through the

FM21 to energize the furnace blower on high speed.

CONDITION:

Cooling - Fan Switch "ON" or "AUTO"

Compressor (Y1) -Heavy Black Line

Reversing Valve (O) -Heavy Gray Line

1 - Reversing valve (O) is immediately energized when the indoor

thermostat is switched to cooling.

2 - On a call for first stage cooling (Y1 & G), indoor blower is ener-

gized on high speed and compressor is energized on low speed.

3 - Additional second stage cooling (Y2), compressor is energized on

high speed.

4 - Outdoor Thermostat (if used) has no effect on cooling.

Page 9

FM21 COMPRESSOR HEATING SEQUENCE - WITHOUT DEFROST OPTION

G(_- INDOORBLOWER

Y I _: ST STAGE COOL/Ia_AT

__ YI

iiii!i

jii!ii_i!:i!!i_

CI::_¸'!

....:iii iiii !iii!iiiii:iiiiii!ii::: :ii iiiii!i

• .-o,...............

IST STAGE CO(]L/HEAT

Y2 _""""'i END STAGE COOL _y:_

Operating Sequence -Compressor Heating:

The diagram above shows the inputsand outputs of the FM21.

The following operating sequence steps through the inputs (left

side of diagram) and the resulting outputs (right side of dia-

gram).

CONDITION:

Constant Fan - Fan Switch "ON"

Blower (G) - Thin Black Line

1 - Blower demand from the thermostat passes directly through the

FM21 to energize the blower in the furnace on high speed.

CONDITION:

Heating - Fan Switch "ON" or "AUTO"

Without Outdoor Thermostat or

With Warm Outdoor Thermostat

Compressor (Y1) - Heavy Black Line

Compressor (Y2) - Heavy Gray Line

1 - On a call for first stage heating (Y1 & G), indoor blower is energized

on high speed and compressor is energized on low speed.

Additional second stage heating (Y2 - if thermostat has 2nd stage

compressor output during heating) energizes the compressor on

high speed,

NOTE -Lennox two-speed heat pumps automatically energize

high speed when outdoor temperature drops below setpoint of

speed control thermostat.

CONDITION:

With Cold Outdoor Thermostat

Furnace (W) - Heavy Black Dashed Line

When outdoor thermostat drops to cold position, compressor (Y1

and Y2) outputs are immediately de-energized. Indoor blower

stops operating and furnace output (W) is energized. When heat

exchanger warms up, furnace energizes indoor blower on low

speed.

Page 10

FM21 AUXILIARY HEATING SEQUENCE - WITHOUT DEFROST OPTION

;i:iii:iiiii_ii

Operating Sequence - 1st Stage Heating:

The diagram above shows the inputs and outputs of the FM21.

The following operating sequence steps through the inputs (left

side of diagram) and the resulting outputs (right side of dia-

gram).

CONDITION:

Auxiliary Heating

With or Without Outdoor Thermostat

Auxiliary Heat (Wl) - Heavy Black Line

1 - On a call for auxiliary heating (Y1, Wl & G inputs), compressor (Y1

and Y2) outputs are immediately de-energized. Indoor blower stops

operating and furnace output (W-output) is energized. When heat

exchanger warms up, furnace energizes indoor blower on low

speed.

Page 11

FM21 EMERGENCY HEATING SEQUENCE - WITHOUT DEFROST OPTION

i!i i i!iiiii ili ii iiiii,i iiiii !i:;;iiii ii:i I'I iiiiiiiiiiiiiiiii!i !

i ....................

I ...................................

Operating Sequence - Compressor Heating:

The diagram above shows the inputsand outputs of the FM21

The following operating sequence steps through the inputs (left

side of diagram) and the resulting outputs (right side of dia-

gram).

CONDITION:

Emergency Heat Switch "ON" (E) - Heavy Black Line

1 - When the emergency heat switch is turned on, the compressor and

indoor blower are immediately de-energized by the room thermo-

stat. The 'E" terminal (input) is energized constantly (not swtiched

by demand) as long as the Emergency Heat switch is turned on. In

this case, without the defrost option, the E terminal has no effect.

CONDITION:

Heating - Fan Switch "ON" or "AUTO"

With or Without Outdoor Thermostat

Heat Demand (Wl) while E is energized - Heavy Gray Line

1 - On a call for heating (Y1 & G), indoor blower and compressor are

locked-out while E is energized.

2- Additional heating demand (W1 - input) energizes the furnace

(W - output).

The indoor blower is energized on low speed by the furnace after

the heat exchanger warms up.

Page 12

FM21DEFROST SEQUENCE -WITHOUT DEFROST OPTION

!!Hii!iii;%ii,iH_iii_¸¸ii ii¸

ii:¸¸i!iii%HAi_ii!!!

ISTSTA_COOW_AT

YI YI

" o ''

Ji;;!%!}

Operating Sequence -Defrost:

The diagram above shows the inputs and outputs of the FM21.

The following operating sequence steps through the inputs (left

side of diagram) and the resulting outputs (right side of dia-

gram).

CONDITION:

Defrost Input (Wl) From Outdoor Unit - Heavy Gray Line

in conjunction with

Heating Demand (Y1 - input)

1 - When the FM21 senses a defrost cycle the defrost indicator LED is

energized.

2 - The compressor continues operating and the furnace is not ener-

gized (locked-out in order to prevent overheating the indoor coil).

Since the furnace is locked-out and indoor coil is cool, the indoor

thermostat may call for auxiliary (W1) heating during defrost.

3 - When defrost is complete, the furnace (W - output) will be ener-

gized to satisfy remaining thermostat demand.

1 -

CONDITION:

Defrost Input (Wl) From Outdoor Unit - Heavy Gray Line

in conjunction with

Auxiliary Heating Demand (Y1 and W1 - input)

Not possible since outdoor unit is de-energized during auxiliary

(W1 - input) heating.

Page 13

FM21COOLINGSEQUENCE-WITH DEFROST OPTION

_ i¸_oo_

oi:_i¸_0ill,i,

iiii_i:iili

i, ii

_=_i:ii;:;::iil]i_......:!!!!E_!i!!:!_!!Li!i!!:!_!!'!!_!!!!_!!i!!!!:L_,ii.__!iiiil;:::::(ii _:;

YI _ ST STAGE COOL/HEAT )

[ ??: : i

i iiili!i

ilil I=i i: iii=i:

I ST STA6E COOL/HEAT _ii

YI _YI

i ii!:i Iii;! i

Operating Sequence - Cooling:

The diagram above shows the inputs and outputs of the FM21.

The following operating sequence steps through the inputs (left

side of diagram) and the resulting outputs (right side of dia-

gram).

CONDITION:

Constant Fan -Fan Switch "ON"

Blower (G) - Thin Black Line

1 - Blower demand from the thermostat passes directly through the

FM21 to energize the blower in the furnace on high speed.

CONDITION:

Cooling - Fan Switch "ON" or "AUTO"

Without Outdoor Thermostat

Compressor (Y1) - Heavy Black Line

Reversing Valve (O) - Heavy Gray Line

1 - Reversing valve (O) is immediately energized when the indoor

thermostat is switched to cooling.

2 - On a call for first stage cooling (Y1 & G), indoor blower is energized

on high speed and compressor is energized on low speed.

3 - Additional second stage cooling (Y2), compressor is energized on

high speed.

1 -

CONDITION:

Cooling - Fan Switch "ON" or "AUTO"

With Outdoor Thermostat

Compressor (Y1) - Heavy Black Line

Reversing Valve (O) - Heavy Gray Line

When outdoor thermostat is warm, previous sequence applies,

Outdoor thermostat acts as a low ambient control for the outdoor

unit, When outdoor thermostat is cold, compressor (Y1 and Y2 out-

puts) are de-energized and indoor blower (G output) continues to

run on high speed.

Page 14

FM21 COMPRESSOR HEATING SEQUENCE - WITH DEFROST OPTION

WARM

COOL

' !!ii!,

2 COMMON

3cool

ii:il

y ST STA6E COOL/HEAT

ii................................ii

YI IST STAGE COQ./HEAT YI

Operating Sequence - Compressor Heating: 2-

The diagram above shows the inputs and outputs of the FM21.

The following operating sequence steps through the inputs (left

side of diagram) and the resulting outputs (right side of dia-

gram).

CONDITION:

Constant Fan -Fan Switch "ON"

Blower (G) - Thin Black Line 1-

1 - Blower demand from the thermostat passes directly through the 2 -

FM21 to energize the blower in the furnace on high speed.

CONDITION:

Heating -Fan Switch "ON" or "AUTO"

Without Outdoor Thermostat 3 -

Compressor (Y1) - Heavy Black Line

Compressor (Y2) - Heavy Gray Line 4 -

1 - On a call for first stage heating (Y1 & G), indoor blower is energized

on high speed and compressor is energized on low speed.

Additional second stage heating (Y2 - if thermostat has 2nd stage

compressor output during heating) energizes the compressor on

high speed.

NOTE- Lennox two-speed heat pumps automatically energize

high speed when outdoor temperature drops below setpoint of

speed control thermostat.

CONDITION:

With Outdoor Thermostat

When outdoor thermostat is warm, previous sequence applies.

If outdoor thermostat switches to cold position during compressor

heat operation, the compressor and indoor blower (Y1, Y2 and G)

outputs are immediately de-energized and the furnace (W-output)

is energized. The indoor blower stops and the fumace begins oper-

ating.

When the heat exchanger warms, the indoor blower is energized

on low speed by the furnace.

If the outdoor thermostat is closed when thermostat demand (Y1

and G input) begins, the compressor and indoor blower (Y1 and G

outputs) are locked-out and the furnace (W-output) is energized.

Page 15

FM21 AUXILIARY HEATING SEQUENCE - WITH DEFROST OPTION

i ..................................................................

sTSTA_ECOOL/HEAT

Yl YJ

Operating Sequence -Auxiliary Heating:

The diagram above shows the inputsand outputs of the FM21,

The following operating sequence steps through the inputs (left

side of diagram) and the resulting outputs (right side of dia-

gram).

CONDITION:

Heating - Fan Switch "ON" or "AUTO"

Without Outdoor Thermostat

Compressor and Auxiliary Heat (Y1, Wl inputs} - Heavy

Black Line

Compressor (Y2 output) -Heavy Gray Line

Blower (G input) -This Black Line

1 - On a call for auxiliary heating (Y1, Y2, W1 & G inputs), furnace (W-

output) is energized along with compressor (Y1 and Y2 output) and

high speed blower (G output).

NOTE -Lennox two-speed heat pumps automatically energize

high speed when outdoor temperature drops below setpoint of

speed control thermostat.

2 - When the furnace warms and the discharge thermostat opens, the

compressor and blower (Y1, Y2 and G outputs) are de-energized.

The blower returns to low speed and the furnace satisfies remain-

ing thermostat demand.

CONDITION:

With Outdoor Thermostat

1 - When outdoor thermostat is warm, previous sequence applies.

2 - When outdoor thermostat switches to cold position, compressor

(Y1 and Y2) outputs are immediately de-energized. Indoor blower

stops operating and furnace output (W-output) is energized. When

heat exchanger warms up, furnace energizes indoor blower on low

speed.

Page 16

FM21 EMERGENCY HEATING SEQUENCE - WITH DEFROST OPTION

iJilit!_iiii_i_;;_ii;!_iilii_i:i!_:ili_ii_!iiiii_ii¸ i:_i_i_i_i_X!!!i_:_il.............................................................................

...................................................... ii

.... z co .

...............................................................................................

iili!i!iii

Operating Sequence - Compressor Heating:

The diagram above shows the inputs and outputs of the FM21.

The following operating sequence steps through the inputs (left

side of diagram) and the resulting outputs (right side of diagram).

CONDITION:

Emergency Heat Switch "ON" (E) - Heavy Black Line

1 - When the emergency heat switch is turned on, the compressor and

indoor blower are immediately de-energized. The "E" terminal (in-

put) is energized constantly (not swtiched by demand) as long as

the Emergency Heat switch is turned on. With the defrost heat op-

tion, the E terminal input energizes a relay in the defrost board to

drop the G fan signal to the furnace and the Y1 signal to the com-

pressor if the unit is in a defrost cycle.

CONDITION:

Heating - Fan Switch "ON" or "AUTO"

With or Without Outdoor Thermostat

Heat Demand (Wl) while E is energized - Heavy Gray Line

1 - On a call for heating (Y1 & G), indoor blower and compressor are

locked-out while E is energized.

2- Additional heating demand (W1 - input) energizes the furnace

(W - output).

The indoor blower is energized on low speed by the furnace after the

heat exchanger warms up.

Page 17

FM21DEFROST SEQUENCE -WITH DEFROST OPTION

y_/_ii_ _i¸¸

WARM

YI _ Isx STA6E_OL/_AT YI

:iii , ,,iiii iii iiiii '

w _o_ .... _ w

_STSTAeeCOOL,_A__

YI i, i i i yi

Operating Sequence -Defrost: 3 -

The diagram above shows the inputs and outputs of the FM21. 4 -

The following operating sequence steps through the inputs (left

side of diagram) and the resulting outputs (right side of diagram).

CONDITION:

Defrost Input (Wl) From Outdoor Unit - Heavy Gray Line

in conjunction with

Heating Demand (Y1 - input)

1 - When the FM21 senses a defrost cycle the defrost indicator LED is

energized.

2 - The compressor continues operating and the furnace (W output is

energized. The furnace operates during defrost.

NOTE- Lennox two-speed heat pumps automatically energize high

speed when outdoor temperature drops below setpoint of speed 1 -

control thermostat..

During defrost, the furnace is cycled on and off by the discharge

thermostat in order to control discharge air temperature.

When defrost is complete, heating demand will be satisfied by either

the furnace or heat pump based on whether the furnace is on or off at

the time the defrost terminals.

If the furnace is ON when the defrost terminates ($89 closed), the fur-

nace will satisfy the Y1 demand.

If the fumace is OFF when the defrost terminates ($89 open) both the

heat pump and furnace will remain off until $89 cools and closes.

When $89 closes, the heat pump will satisfy the Y1 demand.

CONDITION:

Defrost Input (Wl) From Outdoor Unit - Heavy Gray Line

in conjunction with

Auxiliary Heating Demand (Y1 and W1 - input)

Not possible since outdoor unit is de-energized during auxiliary (Wl

- input) heating.

Page 18

FM21SERVICELIGHT SEQUENCE -WITH OR WITHOUT DEFROST OPTION

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i i_ ¸_0_i !

iii ..................................

..................................iil

!iI................................!i_ ii_.................................

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v,............._ ,sTSTA,_C_,_AT V,

iii!!!i i: iii:

Operating Sequence -Service Light:

The diagram above shows the inputs and outputs of the FM21.

The following operating sequence steps through the inputs (left

side of diagram) and the resulting outputs (right side of diagram).

CONDITION:

Compressor Input (Y1) From Indoor Thermostat - Heavy

Gray Line in conjunction with

Service Light (L -input from outdoor unit) and

Auxiliary Heat (W1 -Input from Indoor Thermostat)

1 - When the FM21 senses a closed defrost thermostat during a heating

cycle, the SLCl will begin a 5-1/2 minute (330 sec.) time delay.

2 - If auxiliary heat demand is received after the time delay, the SLCl

energizes the 'L" terminal (output to indoor thermostat) and the ser-

vice light is energized.

Page 19

I[o]_l[o_[o_l

[o_J [o_

[o_J _1

c,Q

TABLE 1

FM21 OPERATION and TROUBLESHOOTING (FM21 Basic Unit)

Input

Unit Room Thermostat

Mode

G I Y1 Y2 Wl I O Y1 G

OFF OFF

Primary

Heating

Auxiliary

Heating

Emergency

Heating

OFF OFF

OFF

OFF I[o]_l[o_J _J

OFF

OFF OFF OFF

OFF OFF I[o]_l[o]_l

[o_ )_1 D_ii OFF

Defrost During

Primary Heat

Defrost During

I[o]_l

*Actually an input used to detect defrost, "On" indicates defrost is bein_ sensed.

**Even though FM21 provides Y2 output, high speed heating is controlled by heat pump in Lennox two speed units.

***Latched in state until Y1 goes off.

tMost heat pump thermostats do not provide Y2 (high speed compressor) output during heating.

$FM21 output is off but voltage from outdoor unit may be measured in some Lennox units.

Response

Heat Pump

Y2 W1 *O

OFF OFF

OFF

Furnace

OFF

OFF$ OFF

OFF

[o_o_.']_l_

c,Q

Unit

Mode G I

Cooling

Primary

Heating

Auxiliary

Heating

Emergency

Heating

Defrost During

Primary Heat

Defrost During

Auxiliary Heat

FM21 OPERATION TABLE 2

and TROUBLESHOOTING (FM21 with Outdoor Thermostat Option)

Input Response

Room Thermostat Outdoor Thermostat Heat Pump Furnace

Terminal 2-3 Terminal 1-2

E (Closed When (Closed When Y2

Cold) Warm)

Y1 Y2 W1

OFF OFF

im--

OFF OFF

OFF

OFF OFF

OFF

*Actually an input used to detect defrost. "On" indicates defrost is being sensed.

OPEN

OFF

OPEN

OPENtt

OFF

OPEN

OFF

OFF OFF

**Even though FM21 provides Y2 output high speed heating is controlled By heat pump in Lennox two speed units.

***Latched in state until Y1 goes off.

tMost heat pump thermostats do not provide Y2 (high speed compressor) output during heating.

$FM21 output is off but voltage from outdoor unit may be measured in some Lennox units.

tSHeat pump cannot go into defrost when outdoor temp. is cold since heat pump unit is de-energized. However, if outdoor thermostat switches to cold position during a defrost cycle, compressor is de-energized

and the furnace completes the heating cycle.

Eo]_l[o_J[o]J_l

[o]_J[o_J[o_l

[o_l[o_J[o_l

[o_J [o_J[o_l

[o_l Eo]J_l

[o]_o_.']_l_ [o]_,J [o]_r-_J [o]_J

[o]_J

[o]_o_.']_l_ [o]_,J [o]_r-_J

TABLE 3

FM21 OPERATION and TROUBLESHOOTING (FM21 with Defrost Option)

Input Response

Room Thermostat Discharge Heat Pump

Unit Thermostat

Mode

Cooling

Primary

Heating

Auxiliary

Heating

Emergency

Heating

Y1 Y2 Wl

OFF OFF

[o_J OFF

OFF OFF

OFF

OFF OFF

OFF

OFF OFF

OFF

[o_OFF

OFF

OFF OFF

[o_

[o]_|.....

_1]11

[o]_J [o]_J

E_o_ [o]_J Eo]_J

[o]_J Eo]_J

Defrost During INN

Primary Heat IHH

OFF

OFF OFF OFF$

OFF OFF$

OFF OFF OFF$

OFF OFF$ [o]_J

[o]_J[o_

OFF OFF$

OFF$

[o_

OFF OFF$

OFF$

[o]_J

Oe,roatOaringINN

Auxiliary

Heat:_

OFF

Terminal 1-2

(Closed When

Cold)

OPEN

[o]_J

*Actually an input used to detect defrost. "On" indicates defrost is being sensed.

OFF

**Even though FM21 provides Y2 output, high speed heating is controlled By heat pump in Lennox two-speed units.

***Latched in state until Y1 goes off.

tMost heat pump thermostats do not provide Y2 (high speed compressor) output during heating.

$FM21 output is off but voltage from outdoor unit may be measured in some Lennox units.

OPEN

OFF

Y2 WI*

OFF OFF

OFF

OFF OFF

OFF

OFF OFF

OFF

OFF OFF

OFF

Furnace

O W

OFF

OFF OFF

OFF

OFF$

OFF$ OFF

OFF$

OFF$ OFF

OFF

¢_-Whendefrost is complete, heating demand will be satisfied by either the furnace or heat pump based on whether the furnace is on or off at the _me the defrost terminals.

If the furnace is ON when the defrost terminates (S89 closed), the furnace will satisfy the Y1 demand.

If the furnace is OFF when the defrost terminates (S89 open) both the heat pump and furnace will remain off until S89 cools and closes. When S89 closes, the heat pump will satisfy the Y1

demand.

Eo]II[o_JEo]_J

Eo]_J[o_JEo_l

Eo_l[o_JEo_l

[o_J Eo_I

[o_l Eo]_J

c,Q

TABLE 4

FM21 OPERATION and TROUBLESHOOTING (FM21 with Defrost Option and 51M28 or 49M57 Thermostat)

Input Response

Room Thermostat Discharge Heat Pump Furnace

Unit Thermostat

Mode

Cooling

Primary

Heating

Auxiliary

Heating

Emergency

Heating

G Y1

[o_l Eo]_J

Defrost During INN

Primary Heat IHH

Y2 Wl

OFF OFF

[o_J OFF

OFF OFF

OFF

OFF OFF

OFF

Terminal 1-2

(Closed When

Cold)

OPEN

OFF

OFF OFF OFF¢

OFF OFF$

OFF OFF OFF$

OFF OFF$ Eo]_J

Eo]_J[o_OFF OFF$

OFF$

[o_

OFF OFF$

OFF$

Eo]_J

Eo]J_l

Oe,roetOaringINN

Auxiliary

HeatY_

OFF

OPEN

OFF

Emergency heat is function of the thermostat.

OPEN

Eo]_J

Eo]J_lOPEN

OFF

OFF Eo]ll

*Actually an input used to detect defrost, "On" indicates defrost is being sensed.

**Even though FM21 provides Y2 output, high speed heating is controlled By heat pump in Lennox two-speed units.

***Latched in state until Y1 goes off.

tMost heat pump thermostats do not provide Y2 (high speed compressor) output during heating.

$FM21 output is off but voltage from outdoor unit may be measured in some Lennox units.

<>Simultaneous Y and W demand will not occur if thermostat is set to add-on dual fuel.

Y2 WI* O

OFF OFF

OFF

OFF OFF

OFF

OFF OFF OFF

Eo]_J

Eo]J_l

Eo]_J

Eo]J_l

Eo]_J

OFF OFF$

OFF$

OFF OFF$

OFF$

OFF OFF$

OFF$

OFF OFF$

OFF$

OFF

€_-Whendefrost is complete, heating demand will be satisfied by either the furnace or heat pump based on whether the furnace is on or off at the time the defrost terminals.

If the furnace is ON when the defrost terminates (S89 closed), the furnace will satisfy the Y1 demand.

If the furnace is OFF when the defrost terminates (S89 open) both the heat pump and furnace will remain off until S89 cools and closes. When S89 closes, the heat pump will satisfy the Y1

demand.

Unit11

Mode

G Y1

Cooling

Primary

Heating

Auxiliary

Heating

Emergen-

Heating

Defrost

During

Primary

Heat

Defrost

During

Auxiliary

Heat_<

TABLE 5

FM21 OPERATION and TROUBLESHOOTING (FM21 with Outdoor Thermostat and Defrost Options)

Inl,ut

Room Thermostat Outdoor Thermostat I DischargeThermostat

Terminal 2-3 Terminal 1-2 Terminal 1-2

(Closed When (Closed When (Closed When Y1 Y2

Cold) Warm[ Cold)

OPEN OFF OFF

OPEN OFF

OPEN

OPEN OPEN OFF

OPEN OPEN

OPEN OPEN OFF

OPEN

OPENer

OPENtt

OPEN

Response

Heat Pump

OPEN

OPEN OPEN

OPEN

Furnace

*Actually/an input used to detect defrost. "On" indicates defrost is bein 9sensed.

**Even mough FM21 provides Y2 output, high speed heating is controued By heat pump in Lennox two speed units.

***Latched in state untiI Y1 goes off.

tMost heat pump thermostats do not provide Y2 (high speed compressor) output durin 9heating.

$FM21 output is off but voltage from outdoor unit may be measured in some Lennox units.

ttHeat pump cannot go into defrost when outdoor temp. is cold since heat pump unit is de-energized. However, if outdoor thermostat switches to cotdposition during a defrost cycle, compressor is de-energized.

_-When defrost is complete, heating demand will be satisfied by either the furnace or heat pump based on whether the furnace is on or off.at the time the defrost terminals.

If the furnace is ON when the defrost terminates (S89 closed), the furnace will satisfy the Y1 demand.

If the furnace is OFF when the defrost terminates ($89 open) both the heat pump and furnace will remain off. un_l S89 cools and closes. When $89 closes, the heat pump will satisfy the Y1

demand.

LENNOX Controls And HVAC Accessories Manual L0806363

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