It’s easy to take our refrigerators and air conditioners for granted. But once upon a time, they were a luxury reserved for the rich. Now, around 97% of homes in the South and 65% of homes in the western United States have a cooling system. But, how exactly do air conditioners work?

In order to understand how an air conditioner functions, it’s important to know about its five main parts and what they do.

An Air Conditioner Has 5 Main Parts:

1. Refrigerant

Refrigerant (also known as coolant or by its brand name Freon®) is a special fluid that is vital to cooling and freezing technology. It operates on a closed loop and carries heat from the inside of your building to the outside. You can think of the refrigerant as the messenger/traveler. We use refrigerant because it changes states from liquid to vapor at convenient temperatures for the refrigeration cycle.

Refrigerant moves through an air conditioner’s cooling tubes and copper coils, connecting the inside unit to the outside unit. It absorbs heat from your indoor air, changing states from gas to liquid. After absorbing heat from the inside air, the refrigerant travels to the outdoor unit where the heat is pushed outdoors.

Once the refrigerant has dispersed its heat outdoors, it changes back to its gaseous state and travels back indoors. After the refrigerant gets cold again, an indoor fan blows air over the cold coils and then circulates cold air through the home. This cycle repeats every time your air conditioner is on.

2. Compressor

The job of the compressor is to pressurize the refrigerant, thus raising its temperature. Due to the combined gas law (a combination of Boyle’s Law, Charles’ Law, and Gay-Lussac’s Law), which states that if pressure increases so does its temperature, when you compress the refrigerant, it will heat up. It does this by squeezing the gas very tightly together.

We heat up the refrigerant in order to get its temperature higher than the outdoor temperature. Since heat naturally flows from a hotter to colder bodies, in order to dispense heat outdoors, the refrigerant must be hotter than the air outdoors. This is why we need the compressor to increase its pressure and thus its temperature.

3. Condenser Coil

The condenser coil is in the outdoor air conditioning unit. It receives the high pressure, high temperature refrigerant from the compressor. You can think of it as the opposite of the evaporator coil. Whereas the evaporator coils contain cold refrigerant, the condenser coils contain hot refrigerant.

The condenser coils are designed to facilitate heat transfer to the outdoor air. The refrigerant releases heat energy with the aid of the condenser fan, which blows air over the coils. As the heat leaves the refrigerant to the outside environment, it turns back into a liquid where it then flows to the expansion valve, which depressurizes the refrigerant and cools it down.

4. Expansion Valve

When the refrigerant leaves the condenser in its liquid state, it has dispersed heat, but it is still too hot to enter the evaporator coils. Before the refrigerant passes to the evaporator coils, it must be cooled down. This is where the expansion valve (also known as a metering device) comes in, normally a thermostatic expansion valve.

Again using the principles behind the combined gas law, which states that when pressure decreases so does its temperature, the expansion valve depressurizes the refrigerant and cools it down.

An expansion valve removes pressure from liquid refrigerant allowing for the refrigerant to change from a liquid to a vapor/gas in the evaporator. It also controls the amount of refrigerant/voltage flow entering the evaporator.

5. Evaporator Coil

Evaporator coils are very important to an air conditioner. It’s where the air conditioner actually picks up the heat from inside your home.

The copper tubes receive the depressurized, liquid refrigerant from the expansion valve. When your indoor air blows over the cold coils, the heat from inside the home gets absorbed. This is because of the 2nd law of thermodynamics which states that heat flows naturally from hot to cold.

Just like the condenser coils need the help of the condenser fan to facilitate heat transfer, the evaporator coils rely on the indoor air handler’s fan (aka the blower) to blow air over the coils.

As the refrigerant absorbs heat from the indoor air, it starts to evaporate to form a vapor.

How the Refrigeration Cycle Works Summary

The return vents, located inside your home, suck in hot air from inside the room. The refrigerant picks up heat as air flows over the evaporator coils, which are very cold.

Once the refrigerant absorbs a certain amount of heat from the indoor air, it then discharges it to the compressor, which pressurizes and heats up the refrigerant. After passing through the compressor, it flows through the condenser coils. A big, often loud condenser fan helps to push air over the condenser coils to facilitate heat transfer outdoors.

Refrigerant then cycles back over an expansion valve, depressurizing it and cooling it down. It then performs the same heat absorption process over and over again.

Now you know about the 5 main components of an air conditioner. If you have any questions about your refrigerant, compressor, condenser, expansion valve, or evaporator, don’t hesitate to contact OnTime Service.

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