Welcome to AC 101: Air Conditioning for Dummies.

Air conditioning units don’t work by magic. They work because of the basic principles of science. But that doesn’t mean they’re easy to understand if you’re not an engineer!

Here’s a brief rundown of how AC units actually work, as simple as it’s possible for us to make it!

Air conditioning for dummies

Image courtesy of Storyblocks.

Air conditioning for dummies: the basics

Okay, so first things first: we have to start with the laws of physics themselves. Don’t worry, it’s not too complicated.

You can’t ‘destroy’ (or for that matter, create) heat, which is a kind of energy. This is called the law of conservation of energy, because the amount of energy in a system always stays the same. So basically, air conditioning doesn’t make the air cooler; it just replaces your hot air with colder air.

The basic way in which air con works is as follows.

  1. The air conditioner sucks in warm air through a grille. The air is sucked in by a fan, the same way that a vacuum cleaner works.
  2. This air flows over a set of pipes called chiller pipes, which contain a cold fluid. As the hot air flows over the pipes, the fluid becomes hotter while the air becomes colder.
  3. Depending on the kind of AC you own, the air might then flow over similar pipes designed to heat the air up. This can be useful in the winter if you want to heat the room up rather than cool it down. But in the summer, this part of the AC won’t be turned on.
  4. A big fan then blows the air back into the room. Over time, this will cool the room down to whatever temperature you like.
  5. The fluid which made the air colder, but absorbed all the heat, now has to be cooled down again. It flows through what’s called a compressor unit and then a condenser unit- more on those later- which makes it cold again.

Air conditioning for dummies: what happens when the air is cold enough?

The AC keeps this process going all the time. It’s constantly sucking in more air, which constantly flows over the chiller pipes. The coolant constantly flows through the compressor and condenser, which keep the fluid cold. This process gradually cools down the air inside your house, until it gets to whatever temperature you set the thermostat to.

When the air gets just a little bit colder than that, the air con stops working and the fan turns off. That’s because if it kept going, the air would get too cold. So the AC unit is designed to turn off as soon as it senses that it has already made the air as cold as you want it to be.

When the thermostat, notices that the air has started to warm up, it turns on again. This happens gradually as your bodies naturally produce warmth. It also warms up your house if you open a door or window and let some more warm air in.


Air conditioning for dummies: but where does the heat go?

If you didn’t know already, the heat has to go outside. Like we said before, the air conditioning doesn’t just make the air in your home colder. It has to absorb that heat and send it somewhere else. That’s why part of the air conditioning unit is inside, and part of it has to be outside. Otherwise, if the whole thing was inside, it would be spewing cold air out the front and hot air out the back!

If you can reach it- don’t try this if your AC unit is on the outside of your apartment!- put your hand just above the fan on the outside part of your AC unit. It should be really hot. If it isn’t, then your air con isn’t working!

The reason the air has to go outside is because of the pesky laws of physics. Those coolant pipes that we mentioned earlier? And the compressor and condenser that absorb all the heat? Well, when you cool that fluid down, you’re still not getting rid of the heat. The fluid gets cooled down by the heat being sent out into the air outside. That way, the heat energy within your house gets transferred outside: no energy gets ‘destroyed’, just sent somewhere where it won’t make you sweat anymore.


Air conditioning for dummies: a few hints and tips

  1. To get the best out of your air conditioning, you have to keep every window and door closed. If you have a window open, air from outside flows in and gets cooled. But then it flows right back outside again! The air conditioning in a car is a great example of this in action.
  2. Make sure a technician services your air conditioner regularly. That way, you can be sure that it’s working at maximum efficiency. If it’s not, your house will take a lot longer to cool down, and you’ll be wasting money on higher energy bills.
  3. Don’t leave the air conditioning on when you leave the house. Contrary to popular belief, it takes way more energy to keep the house cold while you’re away than it does to re-cool it once you’re back!
  4. If you don’t mind the shade, keep the blinds down during the day. This will naturally keep the energy low because the sunshine won’t be coming in. That way, you’ll save save some money on your bills because your air con doesn’t have to work as hard.
  5. If you have the funds, you might want to relocate your thermostat. If it’s sat next to a hot window, or it’s in direct sunlight, it might think that the house is hotter than it is. This will cause the air con to work much harder than it has to.

For a more detailed run down of how you can get the very best out of your air conditioning, check out our post here.