frozen heat pump

Heat Pumps: How and Why Frost Can Develop on the Outdoor Unit

January 28, 2015

Ice is the last thing you want to deal with at any time of year, but it can be quite a nuisance when it forms on your home heat pump on chilly winter days. A frosty heat pump is normal in cold weather, to a degree, but it should never be so iced up that air can’t flow through the unit.

Solid ice around your heat pump’s coils not only prevents it from working properly but can also cause significant damage if you don’t deal with it immediately. Here are some common causes for a frosty heat pump and what you can do about them.

You Don’t Have Sufficient Airflow

Heat pumps must have a space free from any debris, plants and other obstructions. In addition, they have to be up above the ground so that air can flow under the unit. Clear out anything within at least a 3-foot radius of the heat pump. If the unit wasn’t placed above the ground, or if it’s been in place long enough to sink into the ground, then it must be lifted to a position that permits better airflow.

Don’t try to move the outdoor portion of the heat pump yourself. It’s heavy and relatively easy to damage, and you could void any warranty. The unit has to remain level, so your HVAC technician may put it on blocks or on special leveling feet to get the right air circulation.

Extra Water is Coming From Somewhere

Sometimes the key to the mystery of a frosty heat pump lies in the surrounding environment rather than the unit itself. Look around for overhanging trees or bushes that may drip water onto the unit. In extreme circumstances, or if you have the unit improperly covered, excess precipitation may also contribute to the formation of ice.

Check the gutters to make sure they’re in good repair and not dripping onto the heat pump. Gutters need to be cleaned at least twice a year to prevent clogs. A clogged gutter may leak or spill over, as well as contribute to pooling on the roof.

Often, icicles hang off the edge of the roof in the coldest weather due to ice dams, and these may contribute steady drops of water on top of the heat pump unit if the problem isn’t fixed. In addition, check every joint in the gutter for even minor leaks. Seal as needed.

The Defrost Cycle Isn’t Working

Every heat pump has a defrost cycle, because every heat pump does have some ice that builds up around it when weather conditions are right. A typical frosty heat pump never gets more than a thin skin of ice or frost on it before the defrost kicks in.

If you don’t know about the defrost cycle, it can be alarming when the heat pump suddenly starts blowing cold air into your home. This is normal. The unit has temporarily changed the refrigerant direction so that the outdoor coils can heat and melt the ice. You’ll usually see this on days that fall below 40 degrees, and when the relative humidity is at or above 70 percent.

The defrost cycle may run at regular intervals on older units, but most modern heat pumps have temperature and humidity sensors so that it only runs when needed. If an entire cold, humid day passes and you don’t notice a single defrost cycle, then you may need a heat pump repair technician.

Remember that there’s too much ice when it blocks free airflow from getting to the coils. Once you think you’ve remedied the cause of extra icing, shut off the heat pump. Don’t chip off the existing ice; you could damage the delicate structures inside the unit. Instead, follow these steps:

  • Turn on an outside tap, if you have them shut off, and attach a garden hose.
  • Using the hose, rinse the unit until all of the ice melts off.
  • Allow the rinse water to drain.
  • Turn the heat pump back on.
  • If the ice re-forms as thick as it was before, then contact a qualified HVAC technician for a professional in-depth analysis of the problem.

A well-maintained heat pump will not only improve your home comfort, but it will also help save you money throughout the heating season as well.

For more advice on how to deal with your frosty heat pump, contact us at Sun Kool Air Conditioning, Inc. We serve Ocala and the surrounding areas, providing top-notch solutions for all your HVAC needs.

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