How Your Air Conditioning Actually Works

We're simplifying this for you.

It’s time for some science. And we suppose some mechanics as well. We’re talking about your heating, ventilation, and air conditioning (HVAC) system. Everybody knows what their HVAC system is and everybody knows what it does. Do you know how it works though? While it might not be the most exciting topic you can spend the next couple of minutes reading about, there’s quite a bit of value in the knowledge, especially when it comes to diagnosing issues and maintenance.

Today, we’ll be focusing on the cooling process. It may still be early in the year, but you’ll be turning that thermostat down in no time. So let’s dive in before that time comes.

SN Tip: “Air Conditioning,” commonly referred to A/C, is any system that controls the humidity, temperature, and airflow—it’s essentially “conditioning” you air. So when you say turn on the “A/C,” you’re not referring to making it colder.

The first step in the cooling process of air conditioning involves a section of the system known as the blower. The blower blows air, hence “blower.” This fan pushes air from the rooms of your home into the second step of an air conditioning system, which is known as the evaporator.

The evaporator is a collection of coils containing refrigerant liquid often known by a common brand name “Puron.” As air is pushed through the evaporator by the blower, the liquid coolant absorbs heat into the coils from the air. The heat transfer out of the air cools it down while causing the refrigerating liquid to evaporate into a gas, hence evaporator. (Not a lot of creativity was used in the naming of these things).

SN Tip: The EPA’s Clean Air Act mandates that Freon production ends by January 2020. New HVAC units use the Puron refrigerant instead of Freon. As the eco-friendly option, Puron has become the standard in air conditioning. Plus, it may boost your unit’s energy efficiency.

The air blows out of the evaporator and back into your living space at the desired temperature. The refrigerant liquid, now gas, moves into the part of the system that is commonly outside your home where it meets the compressor. This device compresses the coolant vapor, pressurizing it and heating it further.

The hot gas then travels to the condenser, which is the fourth part of the sequence and works in the same fashion as a car radiator. The release of heat causes the gaseous refrigerant to condense back to its liquid state.

The final step before the cycle begins again occurs in the expansion valve. This allows the pressurized coolant to expand, which further cools it down because of chemistry. The cool liquid then travels back into the evaporator where more air from your home is blowing through, and the whole thing starts again.

And that’s how your air conditioner cools your air. It’s not an overly complicated process, but it’s important to know what you’re doing if you’re going to attempt a DIY-fix. And you can always call a professional if you’re not entirely sure what you’re doing.

Diagram of How Your AC works

Alec Lower

Content Writer

Alec is a third-year member of the team at Second Nature. He brings expert knowledge of a myriad of home air filtration topics including HVAC filters, filtration efficiency, and indoor air quality.