What Is a Heat Pump?

By Lyle Weischwill | Mar. 17, 2022 8:06 am PST

Basically, a heat pump is an air conditioner with a reversing valve that can use the refrigerant system to both cool and heat your home. Understanding how a heat pump works requires understanding of how a sealed refrigerant system operates to heat and cool air.

How Does a Sealed Refrigerant System Cool Air?

To understand how a sealed refrigerant system such as an air conditioner cools air, you’ll need to know the function of its major parts. Here’s a description of sealed system parts and what they do:

  • Compressor. The compressor is the heart of the sealed refrigerant cooling system. It’s a positive displacement pump rotated by an electric motor. The compressor receives low-pressure refrigerant gas from the evaporator and rotates to compress that refrigerant to a high-pressure gas that moves through the condenser.
  • Condenser. The refrigerant gets hot when compressed by the compressor pump. The condenser is a heat exchanger that removes heat from the refrigerant gas and condenses it into a high-pressure liquid refrigerant.
  • Expansion valve. The high-pressure liquid refrigerant flows through an orifice in the expansion valve. The orifice converts the liquid refrigerant into a cool mist.
  • Evaporator. The refrigerant mist flows into the evaporator that’s at low pressure. The high-pressure refrigerant mist expands and evaporates. It absorbs the latent heat of vaporization as it changes from a liquid to a gas, which causes the cooling action in the evaporator. The evaporator has metal cooling fins. The blower fan blows air across the evaporator metal cooling fins to cool the air and circulate the cool air throughout your home. The refrigerant flows through the evaporator and back to the compressor where the cycles starts over.
  • Sealed system. The sealed system consists of the refrigerant components described above and the connecting tubing. The entire system is sealed to prevent refrigerant from escaping and air from leaking into the system.

The heat pump thermostat detects temperature inside your home and cycles the cooling system on and off to maintain the set temperature in the cool mode.

How Does a Heat Pump Heat My Home Using Refrigerant?

To heat your home, a heat pump uses a reversing valve in the sealed system to route refrigerant in the opposition direction of cooling flow. Here’s a description of the process:

  1. The compressor pumps hot refrigerant gas through the evaporator and the blower fan blows air across the hot evaporator to circulate warm air through your home.
  2. The refrigerant moves through the condenser. Cold outside air blown across the condenser cools the refrigerant to a liquid state. The heat pump condenser in the heating mode performs the same function as the evaporator in the heat pump’s cooling mode.
  3. The liquid refrigerant flows back to the compressor when it gets compressed and turned into a hot gas that flows back through the evaporator to heat inside air in your home.

A heat pump system typically includes an electric heating element to supplement heat provided by the refrigerant heat during extremely cold days. You’ll see the thermostat indicating the system is using “Emergency Heat” when the electric heating element turns on.

Because your home uses the heat pump year round for heating and cooling, you’ll need to keep the system properly maintained. Schedule an HVAC system tune up twice yearly to keep your heat pump in top shape. Regular maintenance and cleaning will also help your heat pump last longer.

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