Electrical: Heat Pump tips

Short, practical technician tips on electrical for heat pump. Check each one against the manual for your exact model before acting.

Bad run cap = high amps

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A failed run capacitor makes the motor draw excess current, tripping the overload or damaging the motor. Check run caps on every call.

Control circuit vs power circuit

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24 VAC thermostat circuit closes the contactor coil; contactor contacts switch the 230 VAC compressor/fan circuit. Trace problems by separating the two circuits.

Defrosting a frozen coil

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Compressor off, fan on; on a furnace system run heat with all zones calling; on a heat pump run heating but disable electric backup (pull W1 or open the strip-heat breaker) because restricted airflow overheats the elements; clear condensate lines first.

Label thermostat wires by terminal letter, not colour

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Colours aren't standard across brands.

Thermostat must be heat-pump compatible

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Needs O/B, E/W2 etc.