Advanced Air

How a Central Split-System Air Conditioner Works

May 24, 2016

While air conditioners have many complex parts, the way that they cool off your home is pretty simple.

The hardest part to understand is that AC’s don’t actually create cool air, they just remove heat from the air.

Before we go any further, let’s take a closer look at this concept.

Air Conditioning 101: Cold is just the absence of heat

Just like darkness is the absence of light, “coldness” is the absence of heat.

Think about it. How do you make a room dark?

You flip the light switch and draw the blinds. But you didn’t actually “create” that darkness, you just removed light from the room, right?

In the same way, cool air isn’t “created”, it’s simply air that has had heat removed from it.

This heat removal process is the underlying concept of how air conditioners work.

But how exactly does an AC extract heat from the air?

Your air conditioner works like a sponge to absorb heat from inside your home and then dump the heat outdoors.

There are 3 stages that must occur in order for heat transfer to take place:

  1. Evaporation
  2. Compression
  3. Condensation

Let’s explore the stages of this “heat transfer” process:

Photo Courtesy of: Warren Forensic Engineers and Consultants

1st Stage: Evaporation

Evaporation occurs in the indoor unit of your AC (usually located in the attic or basement).

This unit uses a fan to draw in warm air from your home and blow it over evaporator coils filled with cold refrigerant. The cold refrigerant absorbs heat from that air, making the air much cooler. The cold air is pushed back into your home while the heat (captured inside the refrigerant) travels outside to the “compressor”.

2nd Stage: Compression

The compressor increases the pressure of the refrigerant, which raises the refrigerant temperature until it turns into a hot vapor.

Basically, the refrigerant needs to be hotter than the outdoor temperature. This allows the outside air to naturally absorb the refrigerant heat. Once the refrigerant turns into a vapor, the compressor pushes it into the condenser coils.                                                                                                                 

3rd Stage: Condensation

As the compressor forces hot refrigerant gas into the condenser coils, the outdoor air naturally pulls heat from the refrigerant.

A fan also blows air across the hot coils to accelerate the condensation process.

As the refrigerant releases its heat it becomes a cold liquid again. It then travels back to the indoor evaporator and repeats the 3 stages until your house is cooled off.

Have more AC questions?


At Advanced Air, we’re always willing to help our Florida customers get the answers to their heating and air conditioning questions.

Contact us for questions on AC repairs, maintenance or installations.


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