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Savannah, GA & Hilton Head, SC


Douglas, GA

Savannah, GA & Hilton Head, SC


Douglas, GA



AAction Air Conditioning & Heating Co. Blog

Why Does the Outside Unit of the Heat Pump Run in the Winter?

This is a question that puzzles many homeowners. If you’ve ever found it odd that the outside unit of your comfort system runs when you turn on the heat, you are not alone. It’s not something most people are used to, especially if they grew up with a furnace to heat the home. A furnace is separate from an air conditioner, and it contains an indoor unit only (with no outside portion).

But a heat pump is different. A heat pump is an all-in-one heating and air conditioning system. And most of the same components that are used for air conditioning are also used for heating. That means that you can expect to hear the outside unit running when the heat is on.


What makes the outdoor unit necessary for heating your home with a centralized heat pump? We’ll go over the basics here. For more information about heat pumps or to schedule service in Savannah, GA, contact our team.

Refrigerant Isn’t Just for Cooling

One of the main things that confuses people about refrigerant is the name. It may sound that this chemical blend is intended only for cooling (or refrigerating). But refrigerant cannot actually produce cool air.

Heat is an energy, but “cool” is not. That means that you can’t make something cool, necessarily—you can only remove heat so that it cools down. And that’s where refrigerant comes in.

Under the right temperature and pressure, refrigerant is able to absorb heat and move it from place to place. That’s how refrigerant is able to be used for both cooling and heating in a heat pump. It removes heat from the air indoors and brings it outside, when you need cool air. And it absorbs heat from the outdoor air and brings it indoors when you need heat.

A Heat Pump Runs in Reverse

Typically, an air conditioner cycles refrigerant over and over again in one direction. When your heat pump is in cooling mode, it works in exactly the same way.

  • As air from your home moves over the indoor evaporator coil, heat is transferred from the inside air to the refrigerant as it evaporates (turns to gas).
  • Refrigerant moves to the compressor outdoors as a low-pressure gas, where it gains pressure.
  • Heat transfers to the outside air from the refrigerant at the condenser (which is why the outside unit must run in cooling mode—to give the heat somewhere to go) as refrigerant becomes a liquid (condenses).
  • Refrigerant moves to the expansion valve as a high-pressure liquid before losing pressure at the expansion valve and starting the heat exchange process over again.

If you’ve ever put your hand near the outside unit of your AC while it’s in heating mode, you’ll notice it gets warm as it releases heat outdoors. When this process runs in reverse, that heat releases indoors instead. A reversing valve (and some other valves as well) kicks in to allow refrigerant to change direction.

In addition, the condenser becomes an evaporator coil and vice versa. Refrigerant turns to a gas outdoors so it can absorb heat—yes, even when it’s quite chilly out! When it moves back indoors, refrigerant condenses and lets heat release into your home.

And since moving heat is such an efficient process, using a heat pump instead of electric resistance heating for whole-home comfort in the winter can actually cut your spending by about 50%, according to a statistic by the Department of Energy. We recommend Bryant heat pumps for some of the most efficient, effective whole-house heating available for our climate.

AAction Air Conditioning & Heating Co. Inc. provides heat pump services in Savannah, GA. Call us for quality work at a fair price.

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