nest Learning thermostat, Installation And Configuration Manual

Page: 14 / 34

Wiring diagrams: Heat Pump Systems
1 stage heat pump 1 stage heat pump 1 stage heat pump
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.
1 stage heat pump with aux heat 1 stage heat pump with aux heat 1 stage heat pump with aux heat
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 12