empireOfLove2, 1 year ago (edited 10 months ago)

The “exhaust cycle” is defrost. When running in winter heat pump mode the outside coils will freeze over and must be periodically defrosted by warming them back up, else the system will stop moving heat effectively.

Varies by heat pump but some simply have a valve that self recirculates the refrigerant without entering the house, as all the compressor power turns into heat work to melt the ice, and is also why they get noisier.