WIRING DIAGRAMS
O/B
Changeover
Relay*
* Changeover Relay is energized in COOL when O/B switch is in the "O" position
Changeover Relay is energized in HEAT when O/B switch is in the "B" position
Figure 2. Typical wiring diagram for single transformer single stage systems
NOTE
If safety circuits are in
only one of the systems,
remove the transformer
of the system with NO
safety circuits.
CUT AND
TAPE OFF!
HOT
120 VAC
24 VAC
NEUTRAL
* Changeover Relay is energized in COOL when O/B switch is in the "O" position
Changeover Relay is energized in HEAT when O/B switch is in the "B" position
Figure 3. Typical wiring diagram for two transformer single stage systems with NO safety circuits
Optional Jumper for
Single Stage Heat Pump
O/B
Y
G
Changeover
Fan
Relay*
Relay
Compressor
Contactor
* Changeover Relay is energized in COOL when O/B switch is in the "O" position
Changeover Relay is energized in HEAT when O/B switch is in the "B" position
Figure 4. Typical wiring diagram for two transformer single stage systems with safety circuits in BOTH systems
Optional Jumper for
Single Stage Heat Pump
Y
G
Fan
Compressor
Relay
Contactor
Optional Jumper for
Single Stage Heat Pump
O/B
Y
G
Changeover
Fan
Relay*
Relay
Compressor
Contactor
W
C
Optional
Heat
Relay
TWO COMMONS MUST
BE JUMPERED TOGETHER!
W
C
Optional
Heat Relay
W
C
Optional
Heat Relay
TWO COMMONS MUST
BE JUMPERED TOGETHER!
Polarity must be observed. If the HOT side of the
second transformer is jumpered to the COMMON side
of the first transformer a short will be made. Damage
to equipment will occur when power is restored.
R
Limit or
Safety
Switches
ACCESSORY
Limit or
Safety
Switches
COMMON
THERMOSTAT
R
SYSTEM
Hot
24 VAC
120 VAC
Neutral
TRANSFORMER
(Class II Current Limited)
THERMOSTAT
R
Limit or
Safety
Switches
24 VAC
(Class II Current Limited)
NOTE
THERMOSTAT
SYSTEM
24 VAC
120 VAC
24 VAC
Auxiliary
Heating
RELAY N.O.
Transformer
The accessory relay scheme
CONTACT
(Class II
is
Current Limited)
circuits exist in both systems.
COMMON
Limit or
Safety
Switches
24 VAC
120 VAC
Heat Pump Transformer
(Class II Current Limited)
SYSTEM
Hot
120 VAC
Neutral
TRANSFORMER
Limit or
Safety
HOT
Switches
NEUTRAL
NOTE
required
when
safety
HOT
NEUTRAL