Emerson 1F73 Tape OFF, Fan Emergency Relay Compressor Aux Contactor Stage

4 MOUNTING AND WIRING

CONTINUED FROM PAGE 2

O/B/Y2				E/W1
	Y1	G	W2
Changeover				See Note **
		Fan		Emergency
Relay*	Compressor		Aux
		Relay		Relay
			Relay
	Contactor
			(Stage 2)

*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

**Jumper required to use a single Aux Heat for both Second Stage Heat and Emergency

THERMOSTAT

CL R

SYSTEM

SYSTEM

MONITOR

SWITCH

Hot

24 VAC 120 VAC

Neutral

TRANSFORMER

(Class II Current Limited)

Figure 2. Typical wiring diagram for single transformer heat pump systems

NOTE

If safety circuits are in only one of the systems, remove the transformer of the system with NO safety circuits.

		O/B/Y2			E/W1
		Y1	G	W2	C	L
CUT AND
TAPE OFF!		Changeover	Fan	See Note **		SYSTEM
					Emergency	MONITOR
HOT		Relay*	Relay			SWITCH
				Aux	Relay
120 VAC	24 VAC	Compressor
				Relay
NEUTRAL		Contactor
				(Stage 2)
					TWO COMMONS MUST
					BE JUMPERED TOGETHER!

*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

**Jumper required to use a single Aux Heat for both Second Stage Heat and Emergency

THERMOSTAT

R

SYSTEM

Limit or

Safety

Switches

24 VAC	Hot
	120 VAC
	Neutral

TRANSFORMER

(Class II Current Limited)

Figure 3. Typical wiring diagram for two transformer heat pump systems with NO safety circuits

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.

O/B/Y2

E/W1

THERMOSTAT

Y1

G

W2

C

L

R

SYSTEM

Limit or

See Note **

Limit or

Safety

HOT

Safety

24 VAC

120 VAC

Switches

SYSTEM

Switches

Changeover

Fan

Emergency

MONITOR

NEUTRAL

Relay*

Relay

Relay

SWITCH

24 VAC

Auxiliary

ACCESSORY

Heating

NOTE

Compressor

Aux

RELAY N.O.

Transformer

The

accessory relay scheme

Relay

Contactor

CONTACT

(Class II

is

required

when safety

(Stage 2)

Current Limited)

COMMON

circuits exist in both systems.

TWO COMMONS MUST

Limit or

Limit or

BE JUMPERED TOGETHER!

Safety

Safety

HOT

* Changeover Relay is energized in COOL when O/B switch is in the “O” position

Switches

24 VAC

120 VAC

Switches

COMMON

Changeover Relay is energized in HEAT when O/B switch is in the “B” position

NEUTRAL

** Jumper required to use a single Aux Heat for both Second Stage Heat and Emergency	Heat Pump Transformer
	(Class II Current Limited)

Figure 4. Typical wiring diagram for two transformer heat pump systems with safety circuits in BOTH systems

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