Why is my heat pump frosting up in the winter?


Why is my heat pump frosting up in the winter?

Heat Pumps often ice in the winter.

If you see your outdoor heat pump building up ice during the winter, don’t panic. This can be normal during our brief Texas winters. Often, the refrigerant temperatures in the outdoor coils are operating below freezing. The colder it is outside and the longer the system runs, the more frost builds up like the pictures to the left. There are sensors and control boards that should send the heat pump into a “defrost mode” to melt the ice and frost off of the unit. When it is defrosting and the ice melts, you will often see steam if you see it at the correct time. Sometimes customer call in worried that the unit is smoking!

How does it frost up in the winter?

For the more “techy” description: Typically, the refrigerant temperature outside might be 20-25° below the ambient temperature. So if we have outdoor temperatures from 40-50°, the refrigerant could be operating at 15-30°. As the system runs to heat your home, frost can start to develop on the outdoor unit. The colder it is outside, the faster it will build. There are sensors built into the unit to detect this, and it will activate a “defrost mode.” At this time, the outdoor fan will stop running, but the compressor is still operating. Your backup heat should come on to keep your home warm during this defrost time, that can typically last anywhere from a few minutes to 15 minutes and then resume operation again.

Since frost build up varies based on run time, the outside temperature, outdoor humidity level, and size of the unit—accumulation time can vary through out the day.

“What can I do?”

Overall, if the system is keeping the home warm and it is a thin layer of frost, you are probably ok. However, most Heat Pump systems have an “Emergency Heat” setting on the thermostat. By setting the system to this, it will no longer run the heat pump, and will use the back up heat mode (which for us in the Dallas area is usually electric or propane heat). The few days of the year where our temperatures are below 35°, it may be easier to switch to the emergency heat setting to keep the home warm. The Heat Pump efficiency is reduced in extreme temperatures anyhow. Just do not forget to switch back to the regular “Heat” when it gets warmer outside.

As always, we are here to help. If there is a problem — just call us at (972) 296-2604

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Duncanville, TX 75137
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