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Reasons There Is Frost on Your Heat Pump

Heat pumps have become increasingly popular as home comfort solutions. They offer both air conditioning and heating in a single unit, and developments in technology have significantly improved their ability to work energy efficiently during colder weather. As you turn your heat pump to heating mode for the winter, you might notice frost developing along the outdoor coil and cabinet. Is this normal, or a sign that the heat pump needs repairs?

There are a number of reasons for ice on a heat pump. Here are the main ones:

  • Part of normal operation: Most of the time, frost on the outside of a heat pump is nothing to worry about. As the outdoor refrigerant coil draws heat from the ambient air, it also draws moisture. If there is sufficient outdoor humidity combined with below freezing temperatures, the water will turn to ice on the coil. The heat pump has defrost controls to deal with this, and will periodically melt the ice so it doesn’t interfere with the unit’s operation.
  • Broken defrost controls: No mechanical system is 100% malfunction-proof, and the defrost controls that signal the heat pump to go into to the defrost cycle can malfunction, allowing frost to buildup continuously.
  • Broken reversing valve: In order for the heat pump’s defrost cycle to work, it must change the direction that refrigerant moves through the system. This will make the refrigerant coil outside heat up to melt away the frost. Should the valve that changes the refrigerant’s direction break, the defrost control will not be able to activate the cycle.
  • Refrigerant loss: This is a serious possible issue. When refrigerant levels drop because of a leak, it will cause the coil to be unable to defrost the ice. Low refrigerant endangers the entire heat pump (it can cause the compressor to break down) and requires repairs from professionals right away.

If the frost on your heat pump doesn’t melt away after two hours, then something might be wrong with it. Call HVAC technicians to look into the issue.

Red Rock Mechanical LLC provides quality heating services in Burlington, VT and throughout Northwest Vermont and the Plattsburgh, NY area.

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