Why is My Heat Pump Covered In Ice/Frost?

It’s normal for a heat pump to be covered in a bit of frost during the winter. Especially when it’s humid outside after rain.


Because a heat pump in “heat” mode is pulling heat from the outside air and pulling it into your home. When that happens the humidity/moisture in the air around the heat pump becomes frost and clings to the heat pump.

Lucky for you, your heat pump has a defrost mode that starts after 30-90 minutes. So don’t worry.

However, you may have a heat pump maintenance issue if the following occurs:

Heat pump accumulates ice and does not defrost

If your heat pump has been iced over for over 90 minutes, then there’s something wrong with the defrost mode, such as a bad defrost timer or a malfunctioning reversing valve.

A heat pump technician can determine what kind of defrosting system your heat pump has and find the solution.

Heat pump defrosts but frosts over quickly when it’s dry outside

Like we said, it’s natural for a heat pump to frost over quickly because of high relative humidity. But if it’s dry outside and your heat pump frosts over quickly, you may be low on refrigerant.

If that’s the case, a contractor needs to find the refrigerant leak, fix it, and add refrigerant to the heat pump.

Heat pump defrosts but blows cold air into home while defrosting

If you’re getting the cold shoulder from your heat pump while it’s defrosting, here’s why.

When the heat pump starts its defrost cycle, it temporarily reverses to send hot gas to the outdoor coil to melt the frost. Basically, it’s working in air conditioning mode.

To make up for that, the fan in the outdoor unit shuts off. Then your heat pump’s auxiliary heat (either an electric heat strip or a backup furnace) comes on to keep you warm until the defrost cycle finishes.

You’ll know this is working when you see “emergency heat” on your thermostat.

But if you’re not getting any hot air during the defrost cycle, something is wrong with the auxiliary heat, and a contractor will need to repair it.

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Service Champions, your local heating and air conditioning company, serves San Jose, Sacramento, East Bay, and the surrounding areas. For more information on any of our products or services, contact us online.


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