How does an AC work? What is ton? Split vs window AC

If you live in a hot and humid climate, air conditioners are the best solution to keep your home cool. But, how does an AC work? Let’s learn.

Standard AC has 4 main components – Evaporator, compressor, condenser, and expansion valve.


It is the unit placed inside the room. It consists of a heat exchanging coil filled with a refrigerant liquid. The heat from the room enters the evaporator and evaporates the refrigerant.


The compressor as the name suggests, compresses the gaseous refrigerant increasing its temperature and pressure.

How does an AC work?
How do AC works?


The condenser is placed outside the room. It is at a higher temperature than the surroundings. The hot high pressure refrigerant flowing through the condenser coil loses heat to the surrounding. A fan helps the process. The refrigerant changes to a liquid state as it cools.

Expansion valve

The liquid refrigerant (still at high pressure) is made to pass through an expansion valve where its pressure drops. As the pressure drops one part of the refrigerant liquid changes to vapour state. The energy required for this change of state is supplied by the refrigerant itself, thus decreasing its temperature.

The cold refrigerant then reaches the evaporator where a fan blows air over the cool coil. The liquid refrigerant evaporates once again taking heat from the room and the cycle repeats.


Back in the 90s, the most used refrigerant was chlorofluorocarbon commonly known as CFC or freon. Its use came to a halt as it is a major ozone-depletor.

Nowadays most used refrigerants are hydrochlorofluorocarbons (HCFCs) and Hydrofluorocarbon (HFCs). These new refrigerants too have harmful environmental effects.

Split vs window AC

  • In window AC all the components are present in a single unit while in a split AC there are separate units for the evaporator and condenser. The evaporator unit is placed inside the room while the condenser unit is placed outside the room.
  • Split AC makes less noise than window AC.
  • Window AC needs cutouts in the wall for installation.

What is a ton?

Ton signifies the cooling capacity of an air conditioner. A 2-ton AC can cool a larger area than a 1-ton AC. A one-ton AC removes 12000 Btu of heat per hour from a room.

Btu (British thermal unit) is the amount of heat required to raise the temperature of 1 pound of liquid water by 1 degree Fahrenheit at a constant pressure of 1 atmosphere.

This is just a basic explanation of how AC works. There are many other components in an AC that enhance its working.

Quick question

Can evaporative cooler (swamp cooler) work efficiently in hot and humid conditions?

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Answer to quick question

No, evaporative coolers are practically ineffective in hot and humid conditions.

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