In the spirit of going back to school, here’s a lesson in the workings of your central air conditioning or HVAC system (heating, ventilation, and air conditioning). And kids, be grateful – even though summer vacation only started as a way to escape the heat, the school systems kept up the practice even after adopting air conditioning.


Working A/C makes learning and working more comfortable and help filter and ventilate our indoor air. Its main principles also apply to your car, refrigerator, and many other appliances and machines as well. Although air conditioning is over 100 years old, it wasn’t until after 1950 when sales really began to take off. Now, it’s almost impossible to imagine any home or building in the USA without modern air conditioning.

How Air Conditioning Works:

Basic principles to know:

  1. When gas is compressed, it heats up. Conversely, when a gas loses pressure, it cools down. Think about how a bicycle pump heats up when inflating a tire and how when you release air from it, or any other pressurized container, the released gas feels cold.
  2. When a liquid evaporates (becomes a gas), it cools down.
  3. Everything on our planet has some amount of heat energy, even when we think it is really cold outside. All air conditioning systems work by transferring heat from one place to another.
  4. When something changes states, such as from a solid to a liquid or from a liquid to a vapor, heat gets rapidly transferred.
  5. Refrigerant is a special formula that is used to transfer heat in A/C systems, designed to change states at specific temperatures for optimum efficiency and cooling. R-22, a type of Freon, is the refrigerant of choice is most HVAC systems. It’s also referred to as HCFC (hydrochlorofluorocarbon).

Major Components of A/C:


Heat gets absorbed from the room by the indoor air handling system (evaporator) and the compressor pumps the refrigerant to the condenser coils, which release the heat outside.

Evaporator Coil (indoors)

The process starts with the evaporator, where the liquid refrigerant evaporates by getting depressurized. When it loses pressure, it turns into a gas and gets really cold. The cold gas absorbs heat. 

Compressor (outdoors)

The compressor acts as a middle-point between the evaporator and the condenser. When the refrigerant vapor is moving from the evaporator to condenser, it gets pressurized in the compressor and changes into a liquid. The hot high-pressure gas turns into a hot liquid (over 200° F) as it continues to the condenser coils.

Condenser Coil (outdoors)

The hot high-pressure liquid coming from the compressor goes through the many coils that make up your condenser. This gives the gas plenty of time to flow while a large high-power fan blows over them. After the refrigerant’s heat is released with the aid of a fan, the liquid refrigerant cools goes back to the evaporator to start the process again.

Pretty much all air conditioning systems work this way. Heat gets absorbed by the inside evaporator and gets dumped our via condenser coils (called a radiator in your car). Insulated tubing connects the refrigerant to all of your major air conditioning components.

Watch this video for a recap of how air conditioning works:

Read our other blogs for more information on how your HVAC system work and how to maintain it:

Now that you know how air conditioning works, you will better understand how to maintain them. Remember to schedule annual heating and air conditioning maintenance to clean your condenser coils, your evaporator coils, and more.


Air flow is important for your system to work. To extend the life of your central air conditioner and save money on your energy bills, call Interstate Heating & Air Conditioning at (405) 794-8900. We service all makes and models of HVAC systems!

When we come, we’ll teach you all about your how your system works and what you can do to improve its efficiency.

Sign up for our Maintenance Plan for FREE tune-ups and 20% discount on all repairs.

Call us for your in-home evaluation and free estimates: (405) 794-8900.

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Enjoy the school year, Oklahoma, and keep your teachers happy!

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