How to Defrost a Heat Pump

Did you know that the heat pump connected to your HVAC system can freeze? Heat pumps are designed to have a defrosting cycle in order keep them from freezing over, but what do you do if the cycle fails?

Understanding the Defrost Cycle

When frost begins to form, your heat pump will briefly switch from heating to cooling until the frost subsides. Although it sounds strange, the quick switch from heating to cooling will direct warmth towards the coil, which will melt frosty build up. According to NACHI.org, “the heat pump will operate in the defrost cycle until the outdoor coil temperature reaches around 57°F. The time it takes to melt and remove accumulated frost from an outdoor coil will vary on the amount of frost and the timing device of the system.”

Taking Action

Unfortunately there isn’t a whole lot you can do to defrost your own pump once it freezes other than to preemptively take care of potential issues. The first line of defense is to anticipate frosty conditions. Pay attention to the weather and keep the heat pump clear of obstructions such as leaves, branches, or snow. The best way to ensure the defrosting cycle’s success is to keep the coil free from debris, enabling it to do the work on its own.

Depending on the model of your heat pump, you may have to switch the fan on yourself to initiate cooling. If this is the case, directions should be found in your HVAC system’s manual or potentially on the manufacturer’s website.

If you are unsure why your heat pump is not defrosting on its own, the International Associate of Certified Home Inspectors lists several reasons in this article covering the ins and outs of heat pumps. Some of the items on the list include: a broken fan, a bad reversing valve, a bad thermostat, or a dirty coil.

If your heat pump is beyond the point where you can get it moving on its own, the best course of action is to call an HVAC repair specialist for assistance. A professional will be able to identify the potential issue from the list above and quickly help you fix the problem to keep you cozy for home stretch of the winter season.


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