5
69-2738EFS—03
W2 G
W
Y R RC
K Y2
C
MCR33878
HEAT PUMP
CONVENTIONAL
AUX/E
G
O/B
Y R RC
K Y2
C
Conventional Terminal Letters:
Y2 2nd stage compressor contactor.
W2 2nd stage heat relay.
K
Optional wirer save module.
Rc Cooling power. Connect to secondary side
of cooling system transformer.
R
Heating power. Connect to secondary side
of heating system transformer.
W 1st stage heat relay.
Y
1st stage compressor contactor.
G
Fan relay.
C
Common wire from secondary side of
cooling transformer (if 2 transformers).
Heat Pump Terminal Letters:
Y2 2nd stage compressor contactor.
Aux/E
Auxiliary/Emergency heat relay.
K
Optional wirer save module.
Rc Cooling power. Connect to secondary side
of cooling system transformer.
R
Heating power. Connect to secondary side
of heating system transformer.
O/B Changeover valve for heat pumps.
Y
1st stage compressor contactor.
G
Fan relay.
C
Common wire from secondary side of
cooling system transformer.
Terminal Designations
Wiring
