Heat Pump 102: How Does a Heat Pump Work?
Inside the Heat Pump

Heating & Cooling

In Heat Pump 101, you learned the basics about heat pumps and using them to heat and cool your home as well as heat your water. Next, we’ll dive into the inner workings of heat pumps. How do they capture heat from frigid, outside air in the winter, warm your home, and reverse the process in the summer?

Heat pumps rely on the refrigeration cycle to heat and cool your home. The refrigeration cycle consists of four key components: a compressor, a condenser, an expansion valve, and an evaporator.

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Heat pump diagram
Hot and Cold Live Together
Four Components
Air Source Heat Pump - Compressor

The first component, the compressor, is the heart of the system because it is responsible for circulating the refrigerant that will move heat in (or out) of your home. When refrigerant reaches the compressor it’s in a gas state and has a low temperature and low pressure. As the compressor pulls in the refrigerant, it mechanically compresses it to raise the refrigerant’s pressure and temperature. It’s important for the refrigerant to be higher temperature than the surrounding air because it helps with the heat transfer process. The high-temperature refrigerant moves into the condenser where its heat is rejected into the surrounding area. If you’ve ever felt warm air coming from the bottom of your refrigerator, this is your condenser transferring warm air out of the fridge.

When the refrigerant leaves the condenser, it has changed into a liquid state but remains at a high pressure. It then enters the expansion valve, where the refrigerant’s pressure is lowered before it moves into the last step of the refrigeration cycle, the evaporator.

Why Heat Pumps Work in Winter
Air Source Heat Pump - Inside Mechanics

The evaporator consists of an evaporator coil, which is what the low-temperature liquid refrigerant flows through, and a fan. The fan blows the warm air from inside the space across the evaporator coils to cool the air. As the air passes across the coils and cools down, the liquid refrigerant warms up and changes back into a gas state. The refrigeration cycle is now complete, and the refrigerant moves onto the compressor to begin the cycle again.

When you think about the refrigeration cycle, you likely immediately think of cooling. So how does a heat pump, which relies on the refrigeration cycle, provide heating too? Heat pumps are equipped with a unique feature called a switching valve. A switching valve allows a heat pump to reverse the refrigeration cycle allowing it to pull heat from the outside to heat your home during the colder months. Even though it may be cold outside, there is still heat in the outside air a heat pump is able to absorb and use to heat your home. Because heat pumps transfer heat rather than producing new heat, they are 2.5 to 4.5 times more efficient than other heating system options.

Air Source Heat Pump

Now that you understand how the components of a heat pump work, explore the heat pump options for your home or learn more in the Heat Pump Guide.

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