How Does Air Conditioning Actually Work

The AC units are so ubiquitous in our homes and offices that we take them for granted and don’t really think about them until something goes wrong and we need AC repair. If somebody asked you how AC worked, you would probably laugh at the simplicity of the question.

However, if you take a second to really think about it, not a lot of people actually know how it works. All we know is that it cools down the indoor air to a pleasant temperature and that we cannot live without it. If you want to learn a bit more about this important device, read on; hint – it’s pretty much the same as your fridge. The example taken is the split air conditioning system since the majority of American homes have one of these.


Your AC relies on a chemical called refrigerant to cool your house down. This chemical is very good at transferring heat, which makes it an ideal candidate to take the heat out of your indoor air and transfer it outside, as well as cool down the outside air and distribute it inside.

This chemical is kept inside a closed system, which means that it doesn’t get into your air. However, this chemical can lose its effectiveness, or escape the system if there is a leak, which is just one of the reasons why regular maintenance of AC units is important.

Parts of the Air Conditioning Unit

In essence, there are three main pieces to every air conditioning system – the compressor, the evaporator, and the condenser. If you have a split air conditioning system, the compressor and the condenser are located in the outside unit, whereas the evaporator is indoors. The outdoor unit tends to be big, because it needs to have a housing which can withstand the elements, as well as be safe and effective enough to function as a cooling device.

You can have some additional prats, like the ducts going through your house, or an inverter in more advanced air conditioning systems, but these three parts are necessary for an AC to work.

The Air Cycle

The refrigerant cycles to the compressor in the form of a gas, which has low density and low pressure. The compressor compresses the gas, turning it liquid. The liquid is then pushed through the condenser which has fins that dissipate the heat, like a car’s radiator would.

By the time the refrigerant leaves the condenser, it is considerably cooler and ready to cool your house down. The high pressure keeps the refrigerant liquid, regardless of the temperature. However, when the refrigerant reaches the evaporator, it is fed through a small opening, meaning only small amounts of it can reach the indoor unit at a time.

Once the refrigerant reaches the evaporator, the pressure decreases significantly, and the liquid turns to gas. The evaporator looks similar to the condenser, meaning it has the metal fins to facilitate the heat transfer. The refrigerant goes through the evaporator in the similar way it went through the condenser, except now it is collecting heat from the surrounding air, and not dissipating it – the process is reversed.

That leaves the air inside cool, and the refrigerant is sent back to the compressor in the form of a gas to be turned into liquid once again. The fans in the inside unit disperse the cooled air all though your house, or if you have ducts, the air is sucked into the ducts, passed through the evaporator, and then blown out through the ducts once more, this time significantly cooler.

Completing the Cycle

That is a simple example of a cooling cycle. However, the cooling of your house isn’t done in a single cycle. In most cases, several cycles are required to sufficiently cool down your home or your office. Once the thermostat reaches a certain temperature, the AC unit stops working until the temperature rises above the desired level and the cycle begins again.

Seeing how important AC units are in the USA, it is always good to know the basic functioning principle. If anything goes wrong with your AC, you may be able to deduce where the problem occurred and you will certainly be able to understand the explanation that your AC technician gives you.


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