How Do Air Conditioners Work?

Summers can be brutally hot months. If it wasn’t for Willis Haviland Carrier, we would all be sweating indoors to this day. Who is Willis Haviland Carrier? He is the engineering genius who invented and patented the first working conventional air conditioner. No, this is not an article about Willis Haviland Carrier but instead about his wonderfully cooling invention, the air conditioner. The first conventional air conditioner appeared on the market in 1902 and was an immediate hit in the business sector such as industrial warehouses and production plants that were normally sweltering boxes. It wasn’t until around 1928 before air conditioners were available for residential use. Before that, people flocked to department stores and movie theaters to cool off.

Have you ever had the a/c go out in your home or car? It really makes you appreciate the mechanics of pumping cool air all that much more. A few things have changed over the years but the basic principles behind air conditioners have remained the same. But how do air conditioners work? Let’s take a look at the basic system.

Basic Idea of Air Conditioners

An air conditioner is like a refrigerator with a big fan. It uses a gas called freon which is used for various refrigeration purposes as well as a propellant in aerosols. Air conditioners take warm air and make it cooler by using an evaporation process. Then a fan pushed the newly cooled air out into an area. That is basically how it works. Now let’s take a closer look.

Principles Of Hot Air

Air conditioners work by moving heat around. In a central air conditioning system, there are three separate stations. The first station is responsible for extracting heat from the air. The next two stations disburse heat into the outside air. Heat moves easily from place to place, especially if there is a difference in the temperatures. Hot air will readily move into an area where the temperature is cooler. And the bigger the difference in the temperature, the faster the hot air will move. Have you ever opened your car door in the summer? It feels like a blast of heat hitting you right in the face. That is because the air inside is much hotter than the outside air and so it moves quickly out through the door.

How Freon Works


The chemical refrigerant freon has a much lower boil point than water. It doesn’t require a lot of heat for it to boil. An air conditioner contains a set of small pipes that hold the liquid refrigerant. As warm air that comes through the return vent blows across these pipes, the heat from the air is transferred into the liquid refrigerant, which causes it to boil. As it boils it changes into a gas. A basic law of physics is that when a liquid boils and changes into a gas, the gas takes the heat with it.

How Air Conditioners Create Cold Air

When the thermostat tells the air conditioner that the surrounding air is getting too warm, the compressor comes on and starts pumping. It compresses a refrigerant gas, causing it to become a hotter. Next, this hot gas is pushed to the condenser. There the hot gas flows through a set of coils where it dissipates its heat to the surrounding air which is pushed past the coils by a fan. Once the refrigerant gas cools it then condenses into a liquid. Next the liquid flows through the capillary tube. While in the tube, the liquid refrigerant evaporates to become a cold, low-pressure gas. This cold gas flows through a set of evaporator coils which allows the gas to absorb heat. This process cools down the air that passes over the coils, and then a fan pushes this cold air into the room to cool it off.

When warm, moist air blows over these coils, condensation forms which drips down and flows through a tube. This water goes back into the unit and can be used by the condenser coil fan to help cool down the hot condenser coils. This can help to keep humidity levels down in your house.

As the room cools down, the thermostat will measure the temperature. Once the temperature gets below the setting on the thermostat, it sends a signal to the air conditioner and the compressor shuts off.  In some cases the fan may continue to run while the compressor is off. When the room temperature rises above the thermostat setting, then the process begins all over again.