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WIRING DIAGRAMS
Figure 1 – Heat Pump Systems
Figure 2 – Single Stage or Multi-Stage System (No Heat Pump)
with Single Transformer
Heat Pump Connections
If you do not have a heat pump system, refer
to fi gures 2 & 3.
Refer to equipment manufacturers' instructions
for specifi c system wiring information.
You can confi gure the thermostat for use with
the following heat pump systems.
HEAT PUMP TYPE 1 (HP 1). Single stage
compressor system; gas or electric backup.
HEAT PUMP TYPE 2 (HP 2). Multi-stage
compressor or two compressor system with
gas or electric backup.
After wiring, see INSTALLER CONFIGURA-
TION section for proper thermostat confi gura-
tion.
Heat Pump 1
(HP1)
Heat Pump 2
(HP2)
O
Energized in
Cool Mode
B
Energized in
Heat, Off,
Emergency
Mode
No
Output
2nd
Stage
(Com-
pressor)
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
3rd Stage.
Emergency
Mode 2nd
Stage
Heat Mode
4th Stage.
Emergency
Mode 2nd
Stage
Emergency
Mode
1st Stage
Heat Mode
2nd Stage
Heat mode
3rd Stage
Optional*
24 Volt
(Com-
mon)
Diagnostic
Indicator
or System
Malfunction
Switch
24 Volt
(Hot)
Cool
System
Y
W/E
C
L
A1
RC
CLASS II
TRANSFORMER
HOT
24VAC
NEUTRAL
120VAC
24 Volt
(Hot)
Heat
RH
Jumper
Y2
W2
G
Comfort Alert II Module
or Similar System
Diagnostic Module
See Module Instructions
for details
O/B
* Common connection required for diagnostic or malfunction indication.
Single Stage and Multi-Stage Con-
nections
Refer to equipment manufacturers' instructions
for specifi c system wiring information.
This thermostat is designed to operate a
single-transformer or two-transformer system.
You can confi gure the thermostat for use with
the following fossil fuel systems:
SINGLE STAGE (SS 1) gas, oil or electric.
MULTI-STAGE (MS 2) gas, oil or electric.
After wiring, see INSTALLER CONFIGURA-
TION section for proper thermostat confi gura-
tion.
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 A1
L
RC
CLASS II
TRANSFORMER
HOT
24VAC
NEUTRAL
120VAC
24 Volt
(Hot)
Heat
RH
Y2
W2
Jumper
Diagnostic
Indicator
Input
or
System
Malfunction
Switch
Input
Comfort Alert II Module
or Similar System
Diagnostic Module
See Module Instructions
for details
O/B
* Common connection required for diagnostic or malfunction indication.
Figure 3 – Single Stage or Multi-Stage System (No Heat Pump)
with Two Transformers
NOTE: If continuous backlight or hard-
wired power input are desired but do not
function in both HEAT and COOL modes,
cut the heating transformer 24V wires
and tape off. Connect the neutral circuit
disconnected from the heating trans-
former to the neutral circuit of the cooling
transformer. Disconnect the wire to the
RH terminal and install a jumper between
RH and RC. Depending on the system
requirements, replace the cooling trans-
former with a 75VA class II transformer if
needed.
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)
Diagnostic
Indicator
(Optional)
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
Single Stage
3-wire
Zone Valve
application
Blower/Circulator
Fan Energized
Opens
Valve
(4)
Constant
24 Volt
(Com-
mon)
24 Volt
(Hot)
Cool
System
6
Y
W
C
RC
CLASS II
TRANSFORMER
HOT
24VAC
NEUTRAL
120VAC
24 Volt
(Hot)
Heat
(5)
RH
G
Jumper
Closes
Valve
(6)
Figure 4 – 3-Wire (SPDT) Heat Only Zone Valve Wiring