How Does an Air Conditioner Work?

You might assume an air conditioner cools the air in your home, but in reality, it works by removing heat and exhausting it to the exterior. Here’s your chance to learn more about how an AC works.

When you turn the thermostat to “cool,” the air conditioner kicks on as soon as the ambient temperature rises above the target temperature displayed on the thermostat. Then, it goes to work removing heat from the indoor air and exhausting it to the exterior.

An air conditioner works the same as a refrigerator or freezer, except that instead of removing heat from a small space until it reaches a frigid temperature, an AC keeps your entire house comfortable on hot summer days. Refrigerant is the key to refrigeration and air conditioning. By making a loop between the compressor, condenser, expansion valve, and evaporator coil, refrigerant absorbs heat and leaves cooled air to blow back into your home. Here’s how it works.

Air Conditioning Cycle

The refrigerant starts its journey by entering the compressor as a cool, low-pressure gas. The compressor squeezes the refrigerant, packing the molecules closer together and causing it to heat up. This turns the refrigerant into a hot, high-pressure gas as it flows into the condenser, the large box with metal fins sitting on a concrete slab outside your house. A fan blows over the condenser coil while the fins act as a giant heat sync to more effectively remove heat from the refrigerant.

Once much of the heat is expelled, the refrigerant flows out of the condenser as a warm liquid. Next, it flows through an expansion valve on its way into the evaporator coil. This valve expands the liquid refrigerant, causing a drop in pressure that turns it into a cold gas.

A blower connected to the evaporator sends warm indoor air flowing over the coil. The refrigerant inside absorbs heat from this ambient air. Just like the condenser, the evaporator has radiator-like fins to help facilitate as much heat transfer as possible. The blower circulates cooled air around your home, lowering the ambient temperature in the process.

As the refrigerant absorbs heat in the evaporator coil, it becomes a cool, low-pressure gas once again and returns to the compressor to start the trip all over again. The refrigerant cycles between the condenser and evaporator continuously until the thermostat senses that the temperature of your house matches the current setting.


It’s important to understand that air conditioners don’t just remove heat—they also remove humidity. Dehumidification occurs as a natural part of the air conditioning process. After all, because warm air can hold more moisture than cold air, the cooler temperature around the evaporator coil causes water to condense. This is the same principle that makes an ice-cold glass of water “sweat” on a hot summer day. As more moisture collects on the evaporator coil, it drips off into a condensate pan and drains away through the plumbing system.

Dehumidification is an important part of making your home comfortable in the summer, especially in humid climates like Cincinnati. Otherwise, you would feel cool but clammy, prompting you to turn down the temperature further. If your air conditioner isn’t removing enough excess humidity on its own, you can always install a dehumidifier to work alongside it.

Contact Rick’s Heating & Cooling to Learn More

For more information on our cooling products and services, please contact us today and one of our HVAC experts will discuss the solutions you need for your Cincinnati-area home or business.