Installation Manual

Wiring Diagrams: Conventional Heating/Cooling Systems

Conventional 1 Stage Heating



Label:

Function:



Y1

Compressor Relay (Stage 1)

G

Fan Relay

R

24VAC power from heating/cooling

transformer

W1

Heat Relay (Stage 1), Aux heat, Emergency

heat

C

24VAC Common Wire †

*/OB

Compressor Relay (Stage 2), Heat Relay

(Stage 2), Changeover Valve Relay (Stage 1)



Conventional 2 Stage Heating



Label:

Function:



Y1

Compressor Relay (Stage 1)

G

Fan Relay

R

24VAC power from heating/cooling

transformer

W1

Heat Relay (Stage 1), Aux heat, Emergency

heat

C

24VAC Common Wire †

*/OB

Compressor Relay (Stage 2), Heat Relay

(Stage 2), Changeover Valve Relay (Stage 1)



* Fan relay (G) is optional. However, without a G wire, Nest will not be able to control the fan independent of heating.

† Common wire (C) not required in most cases, but strongly recommended.

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