Hive Active Guide D'installation page 10

Terminal descriptions
G – Fan
C – Common wire
W – 1st, 2nd and 3rd stage heating for conventional systems.
W3/AUX is used for auxiliary or emergency heat for heat pump systems.
Y – 1st and 2nd stage cooling or 1st and 2nd stage of heat pump compressor
RC – Cool transformer
RH – Heat transformer
O/B – Heat pump reversing valve
ACC – Accessory terminal for dehumidifiers or humidifiers
(also sometimes called DHUM or HUM)
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