The Working of an Air Conditioner

An air conditioner is a machine that produces heaven on days the sun decides to show its maximum glare. Each of us has definitely waited to reach home from schools, colleges or offices and take a nap under this wonderful machine, especially during summers. But what is the underlying principle of its operation? Let us know!


An air conditioner doesn’t produce cool air but it cools down the existing air in a room and sends it back to where it was taken from. For doing this, it has different components which together form an air conditioning system.

An air conditioner basically has 4 parts and they are an evaporator, a compressor, a condenser and an expansion valve. The main difference between a window AC and a split AC is that while in a window AC all these components are fitted into a single body, in a split AC, the condenser and compressor form the outdoor unit.

Apart from these, there is also a refrigerant which is used to cool the air down. The functions of these different parts and how they produce the result for which they are used is explained below.



A refrigerant is a substance that absorbs heat from the air present in a room and turns into a gas. In this way, the air is cooled and sent out. After traveling through the different sections of the air conditioner, it is again turned back into a liquid. So, a refrigerant is present in both liquid and gaseous states within the system.

Commonly used refrigerants are:

  • Chlorofluorocarbons (CFCs) like R12. These were used once upon a time but are not in use now as they contribute to the greenhouse effect.
  • Hydrochlorofluorocarbons (HCFCs) like R22. These are better than R12 but are still harmful to the ozone layer.
  • Hydrofluorocarbons (HFCs) like R410A, R134. They are safer to the environment as they do not have Chlorine. Moreover, they are highly efficient and offer better air quality.


An evaporator acts as a heat exchanger between the air conditioner and the surroundings. It absorbs heat from the air in a room with the help of the refrigerant. Due to this absorbed heat, the refrigerant evaporates and turns into a gas.


A compressor is the place where the gaseous refrigerant comes and gets compressed, just as the name indicates. This is present in the unit installed outside the house.



The high-pressure gaseous substance from the compressor goes to the condenser and turns into a liquid.

Expansion Valve

The expansion valve controls the amount of refrigerant flow into the evaporator.


When we switch the air conditioner on and set the required temperature, the thermostat (an electronic device) within the air conditioner senses a difference between the set temperature and the temperature of surrounding air. Now, this air goes into the system through a grille and comes in contact with the refrigerant, which absorbs its heat and sends out the cool air. The heat turns the refrigerant into a gas and this becomes a liquid after traveling through the compressor and condenser. The cycle goes on and on.


Image sources: Pinterest, My Daily Alerts, DoItYourself.