Why Has Your Home's Heat Pump Iced Over?

While it’s normal under certain weather conditions for a heat pump coil to be covered in light frost or ice, it isn’t normal for the entire unit to be encased in ice in the winter. If your heat pump has iced over, you need to know why, and what to do about it.

Following is a summary of why your heat pump may be icing over.

Heat Pump Growing Ice?

While heat pumps periodically ice up slightly in the winter, they should go into defrost cycle, freeing the coils and allowing the unit to run as it should.

But why is there frost in the first place? Outdoor air has water vapor, and water vapor has a dew point, or rather, the temperature at which it becomes a liquid. When outdoor air comes into contact with a surface with a temperature below the dew point, the water vapor condenses on that surface. If the surface and air are below freezing, that condensation will freeze.

The refrigerant in a heat pump is usually colder than outdoor air. If the temperature of the refrigerant is colder than the dew point and the freezing point, frost will form.

As mentioned, a little bit of frost is okay, as the heat pump’s defrost cycle should melt it. If frost stays on the unit for more than two hours, or if the heat pump becomes encased in ice, one of the following things could be wrong:

• Defrost control malfunction in the timer, thermostat or sensor
• Reversing valve malfunction
• Wrong refrigerant level, which may be caused by a leak. Frost forms when there’s insufficient refrigerant charge because the coil gets cold without enough refrigerant to gather heat.
• Faulty outdoor fan motor
• Clogged air filter
• Too many closed vents
• Outdoor unit doesn’t match capacity of indoor coil

You may be able to correct some of these problems, but others will need a service pro’s attention.

For more information about what to do when the heat pump has iced over, contact us at Tempco Heating and Air Conditioning. We proudly serve Arlington Heights and the surrounding area.