What measurement can indicate the effectiveness of a heat pump's defrost cycle?

The measurement that accurately indicates the effectiveness of a heat pump's defrost cycle is the temperature rise during defrost. This is because a successful defrost cycle will result in a significant increase in temperature as the heat pump works to melt frost or ice buildup on the outdoor coil. Monitoring the temperature rise allows technicians to assess whether the defrost cycle is operating efficiently and effectively removing the frost.

If the temperature rise is minimal or nonexistent, it may signal that the defrost cycle is not functioning optimally, meaning the heat pump may not be able to maintain efficient operation in cold weather. This parameter directly relates to the heat pump's ability to return to heating mode and continue providing effective heating to the space it serves after the defrost cycle has been completed.

Other measurements, such as air temperature at the outlet, might provide general operational data, but they do not specifically reflect the defrost process's effectiveness. Similarly, the duration of the defrost cycle is important but does not in itself indicate whether the frost was effectively removed. The amount of snow accumulated on the outdoor unit might offer some insight into the conditions affecting the heat pump but does not provide a clear indication of the defrost cycle's effectiveness during its operation.