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How Does An Air Conditioner Work?

Air conditioners are a big part of our daily lives. They are found in many homes and almost all modern establishments in Australia.

But have you ever wondered how air conditioners work? 

In this article, we’ll look at the parts of an air conditioner and the mechanisms involved for it to work. 

A split type air conditioner that releases cool air into a room.

Parts of a Refrigerator

To understand how the cooling process works, let’s first take a look at the key components of an air conditioner.

Evaporator Coil

Evaporator coils are located within the indoor unit of the air conditioner. They contain chilled liquid refrigerant and are responsible for directly cooling the air. 

As the refrigerant passes through the evaporator coil it absorbs heat, which evaporates this liquid into gas. 


As the name suggests, a compressor compresses air which increases the pressure. It is usually located on the condenser unit, the part of the air conditioner that is placed outdoors. 

Modern compressors use a spiral-type compressor known to be space-efficient and quiet. 

Apartment units with outdoor airconditioner units.

Condenser Coil

A condenser coil is located in the condenser unit and is responsible for converting gas refrigerant back to liquid. 

As the refrigerant in a gas state passes through the condenser coil, it cools it down by letting heat escape with the help of a chill fan. 

Expansion Valve

The expansion valve restricts the flow of the refrigerant, which has the benefit of reducing its pressure and also cooling the refrigerant. 

It is usually located in the indoor unit of the air conditioner. 


The refrigerant is a chemical compound usually in a liquid or gas state. It is the liquid that flows through the coils which are directly responsible for the heat exchange process.

Air conditioner technician refilling the refrigerant of an aircon unit.

How an Air Conditioner Works

The basic principle of an air conditioner is to cool the air in a room. It also reduces humidity by removing moisture in the air.

The AC system does this by keeping the evaporator coil inside the room colder than the room temperature and the condenser coil outside the room hotter than the surroundings. 

To explain this in detail, let’s follow the flow of the refrigerant. 

  • When an air conditioner is switched on and the fan starts to spin, warm air is drawn in from the room.
  • This warm air is chilled as it travels over the evaporator coil containing cold refrigerant, before being blown back into the room as cold air.
  • In the previous step, the refrigerant liquid which has absorbed the heat from the air is now converted to gas. This gas then passes through a tube in the wall that is connected to the outdoor compressor. 
  • The refrigerant fills the spaces of the compressor’s piston which compresses the cold refrigerant gas. As the pressure increases in the compressor, the temperature also increases.
  • The compressed gas is then sent to the condenser coil to release the heat which also converts the refrigerant back into its liquid state.
  • This releasing of heat is made easier thanks to a large fan near the condenser that extracts the hot air, blowing it into the outer surroundings. 
  • As mentioned, when the refrigerant loses heat, it condenses and converts back to liquid. However, this cooled refrigerant is still not cold enough yet, so the refrigerant passes through an expansion valve. 
  • The expansion valve restricts the liquid refrigerant’s flow, therefore, reducing pressure and heat at the same time resulting in a colder refrigerant. 
  • This chilled liquid refrigerant is then sent back to the evaporator coil in the indoor unit through another tube in the wall. Then the cycle continues. 
Man has opened air conditioner to expose the aircon filters.

Final Thoughts

I’m sure you now have an idea of how air conditioners work. By knowing this, be able to spot problems with your air conditioners before they become a problem. 

When it does come to that, don’t try to fix it yourself without the right knowledge and tools to do it. Be sure to contact professionals to help you fix it. 

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