nest Learning - Supported Wiring; Nest Thermostat Connector Definitions

Supported Wiring
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Nest Thermostat Connectors 
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Conventional connectors:
Heat pump connectors:
Y1
Stage 1 compressor relay
Y1
Stage 1 compressor relay
Y2
Stage 2 compressor relay, 2nd-speed fan
relay
Y2
Stage 2 compressor relay
G
Fan relay
G
Fan relay
O/B
Not used
O/B
Changeover valve relay
Rc
24VAC power from cooling transformer*
Rc
Not used
W1
Stage 1 heat relay
W1
Stage 1 heat relay
W2/AUX
Stage 2 heat relay
W2/AUX
Auxiliary heat relay
C
24VAC common wire
C
24VAC common wire.
Star *
Stage 3 heat (W3), humidification (HUM), or
dehumidification (DEHUM), 3rd-speed fan
relay
Star *
Emergency heat (E), humidification (HUM), or
dehumidification (DEHUM)
Rh
24VAC power from heating transformer*
Rh
24VAC power from transformer*
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* No jumper wires required. You don’t need to hang on to any old jumper wires going from Rh (sometimes just called R) to Rc. Nest will
automatically jump these two connectors.
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