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Heat Pump 2
(HP2)
Heat Pump 1
(HP1)
O
Energized in
Cool Mode
B
Energized in
Heat, Off,
Emergency
Mode
2nd
Stage
(Com-
pressor)
No
Output
Heat and
Cool Mode
1st Stage
(Compressor)
Blower/
Circulator
Fan Energized
on Call for
Heat or Cool.
Set Elect/Gas
Option for
Emergency
Mode
Heat Mode
2nd Stage.
Emergency
Mode 2nd
Stage
Heat Mode
3rd Stage.
Emergency
Mode 2nd
Stage
Emergency
Mode
1st Stage
Optional*
24 Volt
(Com-
mon)
Fault Indicator
or System
Malfunction
Switch
24 Volt
(Hot)
Cool
System
Y W/E C L RC
CLASS II
TRANSFORMER
HOT
24VAC
NEUTRAL
120VAC
24 Volt
(Hot)
Heat
RH
Jumper
Y2 W2 G
Jumper
Comfort Alert II Module
or Similar System
Malfunction Module
O/B
TYPICAL WIRING 1F85-0477
TYPICAL WIRING DIAGRAMS
Single
Stage 1
(SS1)
Multi-
Stage 2
(MS2)
O
Energized Constantly
in Cool Mode
B
Energized Constantly
in Heat, Off,
Emergency
Mode
No
Output
Cool
Mode
2nd
Stage
Cool Mode
1st Stage
Blower/
Circulator
Fan Energized
on Call for
Cool (and
Heat if
configured
for Electric
Heat)
No Output
Heat Mode
2nd Stage
Heat
Mode
1st Stage
Optional*
24 Volt
(Com-
mon)
24 Volt
(Hot)
Cool
System
Y G W/E C L RC
CLASS II
TRANSFORMER
HOT
24VAC
NEUTRAL
120VAC
24 Volt
(Hot)
Heat
RH Y2 W2
Jumper
Fault
Indicator
or
System
Malfunction
Switch
System Malfunction
Module
O/B
Heat Pump Systems
NOTE: If your system
does not provide an
E connection, jumper
W2 to W/E to use the
Auxiliary Heat in the
Emergency Mode.
* Common connection
required for fault or
malfunction indication.
Single Stage or Multi-Stage System (No Heat Pump) with Single Transformer
* Common connection
required for fault or
malfunction indication.
Single Stage or Multi-Stage System (No Heat Pump) with Two Transformers
Single
Stage 1
(SS1)
Multi-
Stage 2
(MS2)
No
Output
Cool
Mode
2nd
Stage
Cool Mode
1st Stage
Blower/
Circulator
Fan Energized
on Call for
Cool (and
Heat if
configured
for Electric
Heat)
No Output
Heat Mode
2nd Stage
Heat
Mode
1st Stage
Optional
24 Volt
(Com-
mon)
Fault
Indicator
(NOT
USED)
24 Volt
(Hot)
Cool
System
Y G W/E C L RC
CLASS II
TRANSFORMER
HOT
24VAC
NEUTRAL
120VAC
24 Volt
(Hot)
Heat
RH
120VAC
Remove Jumper Wire
between RH & RC
HOT
24VAC
NEUTRAL
CLASS II
TRANSFORMER
HEATING
COOLING
Y2 W2
Jumper
O/B
O
Energized Constantly
in Cool Mode
B
Energized Constantly
in Heat, Off,
Emergency
Mode
152
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