On this install, the factory apparently did not wire up the crank case heater. After finding the wires and putting them on the correct terminals via the schematic, I was looking at the schematic and wondered how the crank case heater becomes energized when there is a two pole contactor. Then, it dawned on me: this is a three phase unit, and there is still one hot leg. So, for those of you who are used to dealing with single phase residential units, this might throw you off, but it’s just the same as a single phase unit with a single pole contactor; the difference is that now we have an additional leg. The heater will de-energize on a call for heat then, because the heater is on the same hot leg. #teachme

Posted by hvac_grammarian at 2021-02-23 18:41:14 UTC