What is the Defrost Cycle of a Heat Pump?

Feb 11, 2019

We rely on our heating system to keep us warm when temperatures drop in the winter months. The heat pump is an integral part of your home’s central heating and cooling system that can both heat or cool down a controlled space.

One of the most commonly reported HVAC problems that we encounter is concerns around steam and other signs that your home’s heat pump is not working properly, but there is typically no cause for alarm. This is simply a sign that the heat pump has entered the defrost cycle, in order to improve efficiency during particularly cold days.

What is the Defrost Cycle?

Heat pumps have both indoor and outdoor components that deliver air at the desired temperature with high efficiency. If the heat pump is operating in the heating mode when the air outside is cool, the pump actually extracts the heat from the air outside and transfers it to the inside of your home to deliver warmth. As such, one of the heat pump’s coils functions as an evaporator while it is exposed to cold temperatures and other winter conditions.

Moisture can freeze and contribute to a buildup of ice that impairs the efficiency of the unit, thus causing the heat pump to go into “defrost mode.” The colder it is outside, the more frequently the defrost sensor will activate the cycle. While the resulting plume of water vapor that arises during the defrost cycle may closely resemble smoke and cause concern, this is merely an indication that the heat pump is operating normally.

Other Signs of the Defrost Cycle

Along with visible signs of steam, you may also hear loud noises or notice water puddles which are all normal parts of a functional defrost cycle. Your heat pump must regularly defrost in order to allow for proper airflow before resuming its operations with improved efficiency. During the defrost cycle, the heat pump’s outdoor motor
stops running, the fan is turned off, and it actually shifts to the cooling cycle so that the outdoor coil is able to warm up and melt the frost.

However, if you notice that your heat pump switches into defrost mode more frequently than normal, it’s important to contact a certified HVAC professional to inspect your unit and diagnose the underlying issue. Contact us at (912) 597-2458 if you need assistance with your heat pump or for any of your heating service needs.

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