nest Learning Installation & Configuration Manual page 17

Dual Fuel - 2 Stage Heat pump, 2 Stage Heat
Label: Function:
Y1 Compressor Relay (Stage 1)
Y2 Compressor Relay (Stage 2)​
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 ‡
, 2nd-speed fan
/ ​ A uxiliary Heat Relay
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