The Defrost Cycle & What It Means

An energy efficient heat pump is a powerful tool to ensure your home has effective air comfort in any season. If you're just becoming interested in this technology, you likely have questions about how one system can provide both cooling and heating. Defrost cycle operation is the key to the latter.

Heat Pump Heating

First, you need to know how a heat pump works. Like a conventional air conditioner, a heat pump uses a pressurized refrigerant to move heat in and out of an environment. It moves the heat out to cool, and moves it back in again to heat.

During the heating cycle, it relies on the outside air to find the heat it puts into your home. There is often plenty of heat necessary to do the job in many cold weather conditions. However, as the temperature drops, frost can start to form on the outside coil. This, as you might expect, can be a problem.

The Defrost Cycle - An Essential Function

Frost build up on the coil can effect performance the same way any dirt or debris would. You experience inferior performance that costs both money and comfort. The defrost cycle is key to ensuring the coil remains frost-free.

When the defrost cycle begins the heat pump temporarily stops heating and switches to cooling mode. This allows the system to bring hot refrigerant into the outside coil to melt the frost. Next, it deactivates the outside fan to increase melting efficiency. When the outdoor coil reaches 57 F, the defrost cycle ends, and normal function resumes.

As noted, the heat pump must stop heating during the defrost cycle. This is an unfortunate, but necessary step. On the good side, the defrost cycle is often short, and a typical heat pump is quick to resume a now much more efficient heating cycle.

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