Defrost Cycle


Heat Pump Defrost Cycle

A heat pump has a cycle called a defrost cycle, which removes the frost from the outdoor coil. A heat pump unit will defrost regularly when frost conditions occur. The heat pump defrost cycle should be long enough to melt the ice, and short enough to be energy-efficient. In the defrost cycle, the heat pump is automatically operated in reverse, for a moment, in the cooling cycle. This action temporarily warms up the outdoor coil and melts the frost from the coil. In this defrost cycle, the outdoor fan is prevented from turning on when the heat pump switches over, and the temperature rise of the outdoor coil is accelerated and increased.

The heat pump will operate in the defrost cycle until the outdoor coil temperature reaches around 57° F. The time it takes to melt and remove accumulated frost from an outdoor coil will vary, depending on the amount of frost and the internal timing device of the system. When the ice melts you may see steam come from the outdoor unit and the unit will make noises that are different from the regular run cycle. During the defrost cycle, the auxiliary heat should run to keep your home comfortable.

If you are having a problem with your heat pump and the defrost cycle, contact Mitchell Mechanical to help you out. We can service any unit, diagnose any problem and help repair any issue you may be having.