How Room Air Conditioners Work | HomeTips
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How Room Air Conditioners Work


Window and room air conditioners use refrigeration principles to extract heat and moisture from room air, cooling and dehumidifying the air.

Diagram of Window Air Conditioner Parts

The basic components inside the unit include a blower and/or fans for moving cooled air into the room and exhausting warm air, and refrigerant components for extracting heat from the air.

Those components include a compressor, evaporator coil, refrigerant-filled tubing, and condenser coil. Most window and room air conditioners have thermostatic controls.

When room temperatures reach the set point of the thermostat, the unit kicks on and the blower draws room air through the air inlet grille and a filter that removes airborne dust and particles.

At the same time, a pump moves a refrigerant through tubing in the unit, initiating the refrigeration process. This refrigerant takes on and gives off heat as it raises and lowers in temperature, changing from liquid to gas and then back to liquid.

When the refrigerant begins to circulate through the indoor coil, it is very cold. As the blower pushes warm air across the coil, the refrigerant absorbs heat and turns into vapor. It travels as vapor to a compressor that pressurizes it and moves it through the condenser coil, where it gives off heat, which is expelled outside. The refrigerant then travels through an expansion device that converts it to a low-pressure, cool liquid again, which then returns to the evaporator coil. And the cycle repeats. All the while, the blower pushes air past the cold coil to chill the air and blow it back into the room.

About Don Vandervort
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Don Vandervort developed his expertise more than 30 years ago as Building Editor for both Sunset Books and Home Magazine. He has written more than 30 home improvement books and countless magazine articles. He appeared regularly on HGTV’s “The Fix,” and served as MSN’s home expert. Don founded HomeTips in 1996.

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