Wiring Diagrams: Conventional Heating/Cooling Systems - nest Learning Installation & Configuration Manual

Wiring Diagrams: Conventional Heating/Cooling Systems
Conventional 1 Stage Heating
Label: Function:
Y1 Compressor Relay (Stage 1)
Y2 Compressor Relay (Stage 2), 2nd-speed fan
relay
G Fan Relay*
O/B Heat Pump Changeover Valve
Rc 24VAC power from cooling transformer
W1 Heat Relay (Stage 1)
W2/AUX Heat Relay (Stage 2) / Auxiliary Heat Relay
C 24VAC Common Wire †
* Star: W3, E, HUM/DHUM, 3rd-speed fan relay
Rh 24VAC power from heating transformer ‡
Conventional 2 Stage Heating
Label: Function:
Y1 Compressor Relay (Stage 1)
Y2 Compressor Relay (Stage 2), 2nd-speed fan
relay
G Fan Relay*
O/B Heat Pump Changeover Valve
Rc 24VAC power from cooling transformer
W1 Heat Relay (Stage 1)
W2/AUX Heat Relay (Stage 2)​
C 24VAC Common Wire †
* Star: W3, E, HUM/DHUM, 3rd-speed fan relay
Rh 24VAC power from heating transformer ‡
* Fan relay (G) is optional. However, without a G wire, Nest will not be able to control the fan independent of heating.
† ​
C ommon wire (C) not required in most cases, but strongly recommended.
‡ ​
U se Rh or Rc in single transformer systems; no jumper wire required. For dual transformer systems, use Rh for the heating
transformer and Rc for the cooling transformer
/ Auxiliary Heat Relay ​
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