How Heat Pumps Work
How Cooling Works
To cool your home, heat pumps transfer heat from the air inside the home to the outside of your home. To perform this function, a heat pump works like a central air conditioning system. It has three main components: a compressor, a condenser, and an evaporator coil. These parts are responsible for converting the working chemical known as a refrigerant from a gas to a liquid and then back again. The indoor unit, which contains the evaporator coil, removes undesired indoor warmth and humidity from the air. The outdoor unit, which contains the condenser and compressor, releases the heat that the indoor unit captured.
The cycle of cooling begins when the refrigerant arrives at the compressor as a cool, low-pressure gas. The compressor then squeezes the refrigerant and packs the molecules of the refrigerant closer together, causing them to increase in temperature. The refrigerant leaves the compressor as a hot, high-pressure gas and flows into the condenser. In the condensing coil, the refrigerant releases its heat. A fan draws outdoor air in through louvers surrounding the outdoor cabinet and blows air across the hot coil. As the air blows across the coil, it transfers the heat to the outside air and cools the refrigerant inside the coil.
Once the refrigerant leaves the condenser coil, its temperature is much cooler, and it has changed from a gas to a liquid. The refrigerant then flows indoors through tubing and passes through a small opening in the expansion valve. In this valve, the refrigerant expands and the liquid’s pressure drops, and it becomes a low-temperature, low-pressure liquid that flows into the evaporator coil. Once here, it evaporates and absorbs heat from the return air, which blows over the indoor coil due to a fan. At the same time, moisture in the air is removed as it condenses on the indoor coil. Humidity removed from the air, as it makes contact with the indoor coil, then collects in a pan at the bottom of the coil and finally flows to a drain or pumps to a drainage receptacle. And voila, your home is comfortable even when there are sweltering temperatures outside!
How Heating Works
When an air-source heat pump is heating your home, the cooling cycle is reversed. In the outdoor unit, the heat pump evaporates a low temperature refrigerant. As the liquid evaporates, it absorbs heat from the outside air. A heat pump can do this because heat exists in all air even down to absolute zero (-460 F or -273 c). Even cold winter air contains heat.
After the gas is compressed in the outdoor unit’s compressor, it passes into the indoor coil and condenses; this releases heat to the inside of the house. The pressure changes caused by the compressor and the expansion valve then allow the gas to evaporate at a low temperature outside and condense at a higher temperature indoors. All this work lets you come home to a warm, comfy house, even where it’s crisp and cold outdoors.
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