During the winter, the cool surfaces of your heat pump provide the perfect place for water to condense out of the air, which soon freezes if the ambient temperature is cool enough, forming frost on the outdoor coil. A thin layer of frost is normal, and is removed by the system’s defrost cycle when necessary, but if you have an extremely frosty heat pump, it may be necessary to call in an HVAC professional.

The Defrost Cycle

During the winter, your heat pump uses a refrigerant to absorb heat from the outdoor air and release it inside. As the coolant absorbs heat, the outdoor lines cool, allowing any water on the outdoor coil to form frost. The defrost cycle reverses the flow of the refrigerant, putting the system temporarily into air conditioning mode, but without the outdoor fan running. Hot refrigerant cycles through the outdoor coil, melting the frost, while indoors, the indoor coil temporarily cools the air. Supplemental heating is used to warm the indoor air until the defrost cycle is over. The defrost cycle happens automatically on most systems, unless the system is malfunctioning.

Preventing a Frosty Heat Pump

In some cases, a frosty heat pump can easily be avoided, using the following steps:

  • Clear debris such as leaves and grass from around the outdoor coil and from its fan, which could prevent proper air flow. Carefully remove any debris caught in the cooling fins.
  • Make sure that there is no water dripping onto the outdoor coil from nearby sources such as leaky gutters.
  • If ice forms on top of the outdoor unit, turn the system off and remove the ice to prevent the entire coil from freezing over. Use a garden hose to melt any frost that has formed on the coils themselves.

In most cases, however, a frosty heat pump is caused by a major system problem, such as a bad defrost control or improper refrigerant level, requiring the services of an HVAC professional.

For more information about repairing a frosty heat pump, call our HVAC experts at Pruett Air Conditioning, serving the Warner Robins and Eastman areas.

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