nest Learning thermostat - Wiring Diagrams: Heat Pump Systems

Conventional 2 stage heating and 1 stage cooling
Conventional 2 stage heating and 1 stage cooling
Conventional 2 stage heating and 1 stage cooling
Label
Function
Y1
Compressor Relay (Stage 1)
Y2
Compressor Relay (Stage 2)
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 connector: W3, E, HUM, or DHUM
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.
† Common wire (C) not required in most cases, but strongly recommended.
‡ Use 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.
* 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.
‡ Use 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.
* 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.
‡ Use 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.
Conventional 2 stage heating and 2 stage cooling
Conventional 2 stage heating and 2 stage cooling
Conventional 2 stage heating and 2 stage cooling
Label
Function
Y1
Compressor Relay (Stage 1)
Y2
Compressor Relay (Stage 2)
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 connector: W3, E, HUM, or DHUM
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.
† Common wire (C) not required in most cases, but strongly recommended.
‡ Use 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.
* 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.
‡ Use 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.
* 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.
‡ Use 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.
Nest Learning Thermostat installation & configuration guide Page 10