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How do Room Air Conditioners Work?

Last Updated: June 9, 2021

How do Room Air Conditioners Work?

Room air conditioners remove heat from indoor air and transfer it outdoors. Cool air is then returned to the room. The cycle continues until the indoor air reaches the “set point,” or the desired temperature on your thermostat.

Cool refrigerant gas is pumped into the compressor where it is—you guessed it—compressed, which heats the refrigerant. The hot refrigerant gas then passes through the condenser coil, where it is cooled, and changes from a gas to a liquid. This liquid runs through an expansion device, which further cools the gas as it enters the evaporator coil. This cooler gas collects moisture (in the form of water beads on the outside evaporator coil surface) and heat from the air to be cooled. The cooled air is then returned to the room and the process repeats until the room temperature reaches the desired set point.

The compressor pumps and heats the refrigerant, increasing the temperature and pressure of the gas. The hot gas passes through coils, loses heat and condenses into a liquid. This liquid runs through an expansion valve and evaporates to become cold, low-pressure gas. The cold gas passes through a set of coils that cools the air. A fan blows the cool air into the room.

Your air conditioner also removes moisture from the air, which makes the room feel much more comfortable.

An air filter traps airborne dust, dirt and debris, keeping the inside room air cleaner by maintaining evaporator coil cleanliness. Regular filter cleaning helps ensure this important function’s effectiveness and prolong the life of a unit.

My grandmother has a Friedrich Quietmaster at her house, which she likes to keep very cold. Everyday in the summer she has it on high and the temperature on cold. For 44 years the unit was in operation from April to October. Just this summer it gave way and we got a Friedrich Kühl. I’m really impressed with the quality.


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About the Author | Holly Beck

With more than 15 years of experience, Holly Beck is Friedrich’s Director of Marketing. In her role, she works with clients and customers to enhance and broaden Friedrich’s brand, both on- and offline. Holly's passion for innovation and connecting strategy to customers has made her integral in key strategic initiatives at Friedrich, including driving the company’s digital transformation and newly-launched website, as well as PR, advertising, product launches, and marketing program initiatives. Her commitment to overseeing and advancing Friedrich’s community goodwill and philanthropic efforts–ranging from assisting with hurricane recovery efforts to providing relief for homeless and youth shelters, schools and more–has benefited dozens of worthy nonprofit organizations and improved the lives of others in need. Holly’s family, including her young son, daughter, and husband are paramount in her life, and she considers herself blessed to also be part of the Friedrich “family” of valued colleagues, co-workers, and friends.