What happens to the compressor in reverse cycle heat pumps during the defrost cycle?

During the defrost cycle of reverse cycle heat pumps, the compressor operates only partially. This process is necessary because, in colder conditions, the outdoor coil can accumulate frost or ice, which reduces the heat pump's efficiency. During defrosting, the system temporarily changes the refrigeration cycle to melt the accumulated frost.

In this state, the compressor is still running, but it is not operating at its full capacity or in the same manner as during normal heating operation. Instead, new heating and cooling processes are initiated where the flow of refrigerant is reversed. This is essential to heat the outdoor coil, allowing it to melt the ice.

Full operation is not maintained because the system needs to conserve energy and efficiently manage the transition for thawing. Complete stopping, continuous operation, or partial operation at normal levels do not align with the design and function of the defrost cycle in heat pumps.