NOTE
The following wiring diagrams show typical terminal identification and wiring. For proper installation, refer to
the original manufacturer's instructions.
Relay contacts shown are thermostatically operated.
FAN
AUTO
Heat or Cool
FAN ON
FAN
AUTO
Emer
EMERGENCY
Thermostat
Control
Circuit
MALF
THERMOSTAT
O/B |
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| W2 |
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Changeover |
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| MONITOR |
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Relay* |
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| SWITCH |
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| Compressor |
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| Contactor |
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| 24 VAC |
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* Changeover Relay is energized in COOL when O/B switch is in the “O” position |
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| Changeover Relay is energized in HEAT when O/B switch is in the “B” position |
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Figure 3. Typical wiring diagram for single transformer 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
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120 VAC |
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NEUTRAL
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| FAN ON |
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| Thermostat |
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| FAN |
| FAN |
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| Control |
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| EMERGENCY | Circuit |
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| AUTO |
| AUTO |
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| Heat |
| Emer |
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O/B | Y | G |
| W2 | E | C | L |
Changeover |
| Fan |
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| Emergency | SYSTEM |
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| MONITOR |
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Relay* | Relay |
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| Relay | SWITCH |
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Compressor |
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| Aux/Emer |
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| Contactor |
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THERMOSTAT
R
SYSTEM
Limit or
Safety
Switches
Hot
24 VAC |
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| 120 VAC |
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TWO COMMONS MUST
* Changeover Relay is energized in COOL when O/B switch is in the “O” position BE JUMPERED TOGETHER! Changeover Relay is energized in HEAT when O/B switch is in the “B” position
Neutral
TRANSFORMER
Figure 4. Typical wiring diagram for two transformer systems with NO safety circuits
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| Thermostat | MALF |
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| FAN | FAN |
| Control |
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| EMERGENCY | Circuit |
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| AUTO | AUTO |
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| Heat | Emer |
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O/B | Y | G | W2 | E | C | L |
NOTE
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.
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R | SYSTEM |
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| Limit or |
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| Safety | 24 VAC |
| Switches | ||||||
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Changeover
Fan
Emergency | SYSTEM |
MONITOR |
Switches |
NEUTRAL |
Relay*
Compressor
Contactor
Relay
Relay | SWITCH |
Aux/Emer
Relay
(Stage 2)
TWO COMMONS MUST
BE JUMPERED TOGETHER!
24 VAC |
ACCESSORY |
RELAY N.O. |
CONTACT |
COMMON |
Limit or |
Safety |
Switches |
Auxiliary
Heating
Transformer
NOTE
The accessory relay scheme is required when safety circuits exist in both systems.
Limit or
Safety
Switches HOT
*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
COMMON |
| 24 VAC |
120 VAC
NEUTRAL
Heat Pump Transformer
Figure 5. Typical wiring diagram for two transformer systems with safety circuits in BOTH systems
3
