How Do Air Conditioners Work?

An air conditioner works by drawing heat energy from the inside of your home and expelling it to the outside. As heat is removed, the cooler air is blown back into your home. This process is repeated until your home reaches your desired temperature as set on your thermostat.

This is a simplified explanation. Air conditioners are complex systems that comprise various mechanisms and processes. But you don’t need to be an expert in thermodynamics to understand how an air conditioning works. This article will provide a simple step-by-step explanation.

Exterior shot of air conditioning units against colourful wall

Evaporator coil, condenser coil and refrigerant

An air conditioning system contains two connected coils. One of these coils is called the ‘evaporator’ and is located inside the home. The other coil is called the ‘condenser’ and is located outside the home

Flowing through these coils is a substance called ‘refrigerant’. Refrigerant has a low boiling point; it transitions between a liquid and a gas state with little temperature change. This makes it perfect for use in an air conditioning system.

Step 1 — the evaporator

Hot indoor air travels into the air conditioner through a grille, typically found at the bottom of the unit, where it reaches the ‘indoor’ coil, known as the evaporator. The refrigerant in this coil is cool and in a liquid state. As hot air reaches the evaporator, the heat is transferred to the refrigerant, cooling the air but heating the refrigerant. Due to its low boiling point, the transfer of heat energy causes the refrigerant to evaporate into a gas. Essentially, the refrigerant absorbs heat energy, leaving the remaining air cool. A fan blows the cool air back into your home.

Though cool air has been successfully released into the room, the process is far from over. The heat energy now needs to be expelled outside so that the process can repeat. This leads us to the remaining stages.

Step 2 — the compressor

As the gas moves along the coils, it reaches a component known as the ‘compressor’.

The compressor is located outside. The function of the compressor is to increase the pressure of the gas. When pressure increases, as does temperature, and so the refrigerant leaves the compressor at both a high pressure and a high temperature. The compressor heats the refrigerant up to a temperature that exceeds the temperature outdoors.

Step 3 — the condenser

As the hot, gaseous refrigerant reaches the outdoor coil, known as the ‘condenser’, it comes into contact with the outdoor air.

The air outside is hot, but, crucially, it is still cooler than the refrigerant. This causes the refrigerant to condense and enables the transfer of heat from the refrigerant to the outside air. This process of heat transfer is assisted by a fan, which blows the heat outside.

Step 4 — the expansion valve

Next, the gas travels to the expansion valve. The function of the expansion valve is to restrict refrigerant flow; this reduces the pressure of the refrigerant. The rapid reduction of pressure causes the liquid to boil, a process that requires extra energy to complete. That energy comes from the refrigerant itself, and as energy is expended, the mixture cools, leaving cool refrigerant liquid that returns to the evaporator, ready to start the process all over again. The process continues until enough heat has been drawn out of the room to match the temperature on your thermostat.

Here at FM Mechanical, we’re experts in air conditioning. We offer installation, services and repairs on a range of industrial and domestic air conditioners from the world’s most reliable manufacturers. With over 30 years of experience, we guarantee to offer a service that is efficient and effective. Contact our team to learn more about our services.