How Your Air Conditioner Works

Originally published on November 12, 2021

Understanding AC Systems: A Behind-the-Scenes Look

While most people associate air conditioning with cold, the science behind making your home cooler actually deals with the transfer of heat. When that heat is lost, or removed, the remaining cold air cools your home.  In order to understand this system better, let’s look at the major components. Your central air conditioning system has two key components: the indoor unit, and the outdoor unit. They work in tandem to keep your home comfortable year-round.

Indoor Unit

The indoor unit is typically located in a closet or basement, and is near where your furnace filter is located. The unit consists of a coil box that contains what is called an evaporator.  The evaporator allows for the refrigerant – a cooling fluid inside the coil piping sometimes known by a brand name such as Freon™ – to evaporate and absorb heat. Once the heat is absorbed from inside your home, it leaves nothing but cool air to be sent back into your home.

Just as water absorbs heat from your stove in order to boil (or evaporate) refrigerant absorbs heat from your house. This means that both water and refrigerant turn from liquid to vapor as they absorb heat.

Outdoor Unit

The outdoor unit is usually located in the rear or side of your house and it is where the heat from inside your home is dispersed. It contains the compressor, condenser coil and a fan. The heat absorbed from your home’s air is transferred to the refrigerant and then pumped to the outdoor unit. As this heat is absorbed and moved by the refrigerant to the outdoor coil, it passes through the compressor.

The compressor in your air conditioning system has the primary job of moving the refrigerant throughout the system. This is important as we can then keep reusing the refrigerant to cool our house. The refrigerant is compressed to a higher pressure, and moved through the outdoor coil known as the condenser. As the refrigerant passes through the condenser, a fan delivers ambient air across the condenser coil causing it to cool.

As the process completes, the heat from inside your house is dispersed to the air outside your house. The refrigerant is then pumped back indoors and the whole process repeats.

Did you know that making your home cooler was actually less about increasing cold air and more about removing existing heat?

How an Air Conditioner Works

How an Air Conditioner Works

How a Heat Pump Air Conditioner Works

How a Heat Pump Air Conditioner Works

How a Geothermal Air Conditioner Works

How a Geothermal Air Conditioner Works

How a Geothermal Heat Pump Air Conditioner Works

How a Geothermal Heat Pump Air Conditioner Works

Related Articles
Simple Ways to Extend the Life of Your AC and Heating System

Was this helpful?
Vote This Post Up 130 Loading...

20 thoughts on “How Your Air Conditioner Works

  1. A dog chewed the wire to the outside air compressor and the fuse box is now off. But the fuse box for the inside unit is on and seems to be running constantly. Will this hurt the evaporator in side it? Should I shut them both off till a repair man can come and look at it?

  2. recently we had our air conditioner “tuned up” for the summer . The person who did the work said our compressor had dropped from “35 to 31” and would soon need replacing. No matter what question I asked he could not explain (or I could not understand his explanation!). what did he mean and should I have the compressor changed now.

    • We usually recommend getting several quotes from different contractors before making HVAC investment decisions. This is not just to get the best price. It is also important that you and your contractor are on the same page with what you want to be done with your system.

  3. Hi Rob – you would need to match a new indoor coil with the new outdoor to achieve a larger capacity or better efficiency rating. While a mismatched set might still function (if both are designed for the same refrigerant) it will not achieve the ratings of the new outdoor. Hope this helps answer some of your questions.

  4. Our current ac is not cooling our house enough. If we wanted to get something bigger, would we have to replace both inside and outside units or could we just get a bigger outside unit (I saw one for sale recentlt)?


  5. Scott, this was a great article about how air conditioners work. I had no idea that air conditioning was split up into two units, the indoor unit and the outdoor unit. My husband and I are house hunting right now. We will have to keep our eye out for homes that have outdoor units as well as indoor ones.
    Emily Smith

Let us know your thoughts

Your email address will not be published. Required fields are marked *