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How HVAC Experts Defrost a Heat Pump

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Some Cincinnati area homeowners have trouble with their heat pump freezing up in winter. This problem prevents your home from receiving the heat it needs and has the potential to damage your heating system. We share tips on thawing a heat pump so you are prepared to take action if this issue occurs.

Why Do Heat Pumps Ice Up?

In a nutshell, it’s all about the water vapor. Even the cold, dry air outside your Cincinnati home contains small amounts of water vapor. When it reaches its dew point, the water vapor undergoes a phase change into liquid form.

Now consider your heat pump’s refrigerant runs up to 20 degrees colder than the air outdoors. If the cold weather is just right — around 20 to 40 degrees with a relative humidity above 70 percent — there’s a good chance that frost will form all over the condenser coils.

To prevent frost formation, a heat pump occasionally undergoes a defrost cycle. This essentially takes all of the heat that’s being transferred inside your home and instead sends it back outdoors through the condenser coils, thus melting the ice that forms around the unit.

Unfortunately, this may not be enough to remove severe ice formation. In some cases, an underlying problem may prevent the defrost cycle from working. As such, it is important you know the steps to thaw a heat pump manually to protect your unit.

How to Defrost a Heat Pump

If your heat pump has visible ice accumulation, follow these steps for thawing a heat pump:

  • Turn the heat pump off at the circuit breaker. You don’t want it to suddenly energize while you’re working on the problem.
  • Next, grab a garden hose and spray the heat pump with water until the ice melts. Hammering or chipping away the ice could cause major damage.
  • If it’s warm enough, you can reactivate the heat pump and run it on “fan” mode until the ice melts.

Once you’ve defrosted your heat pump, you need to determine if there is a clear and correctable source that caused your unit to freeze over. One common culprit is a leaking overhead gutter. Damage or improper pitch causes water to spill out of the gutter onto the heat pump below where ice forms. If you notice a gutter leak, make repairs right away to prevent further problems with your heat pump.

Your Heat Pump’s Defrost Cycle

All heat pumps, regardless of the age, have a built-in defrost cycle. This is the system’s method for defrosting a heat pump. The older units have a mechanical timer that triggers the cycle, while newer units are controlled by a solid state control module and temperature sensors. Either way, the system itself works the same. 

A well-running heat pump should run in defrost mode at timed intervals and can run from 30 seconds to a few minutes. The defrost cycle helps rid the outdoor unit of frost and ice buildup to prevent the system from freezing over.

The entire system is reversed as the air conditioning is turned on, which causes the refrigerant to heat up and run through the outdoor coil to melt ice. The outdoor fan is stopped to prevent it from cooling the outside coil. The defrost will continue until the temperature of the outside coil reaches about 57 degrees.

During the heat pump’s defrost cycle, the indoor fan continues to run, and your system is in cooling mode. In order to avoid cold air from circulating throughout the house, a backup heating system can be utilized when the pump goes into defrost mode.

My Defrost Cycle Isn’t Working

There are several reasons why your heat pump defrost cycle isn’t working properly. An older system may begin running the cycle when it isn’t necessary. In other cases, the defrost cycle may not come on when it needs to, which can damage the heat pump. There are a few reasons this may happen:

  • Wiring problems
  • Thermostat malfunction
  • The outdoor coil is dirty or covered with debris

If your heat pump defrost cycle doesn’t kick on periodically, it’s likely not defrosting the ice. And, if your heat pump ices up too far, the cycle doesn’t have the power to remove such buildup. There are many causes for the defrost cycle to not work, and most of them have to do with the internal parts of the heat pump itself. You need to call for HVAC service to have such issues corrected. When the defrost cycle fails, it falls on you to protect your system by knowing how to dethaw a heat pump.

Heat Pump Repair from Apollo Home

If your heat pump’s defrost cycle does not work or the steps how to thaw a heat pump do not get rid of ice, it’s time to call for help. Call Apollo Home today for quick and reliable heat pump repairs to eliminate ice and restore proper cycle functioning.

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