If you’ve had air conditioner repair lately, you may have had a problem with your compressor. So what is a compressor, and what does it do? And where does it fit in the function of an air conditioner? Let’s find out!

air conditioning compressor

Image courtesy of Storyblocks.

When was the idea of compressing air or gas in order to control temperature discovered?

The relationship between pressure and temperature was discovered way back in 1820, by English inventor Michael Faraday. Faraday was an absolute pioneer in both physics and chemistry, whose work touched on magnetism, electricity and the discovery of a number of elements in the periodic table. We know him today for the Faraday cage, but also gave his name to the Faraday Effect, the Faraday Constant, the Faraday Wave, the Faraday Paradox and at least a dozen more scientific terms. While Faraday himself didn’t invent air conditioning units- he probably didn’t have the time- he did discover that by compressing and then liquefying ammonia, he could cause the air temperature to drop. This is the basis of how modern compressors work.

Because of the scale of his experiment, he couldn’t find a use for it. But later in history, somebody else did.

Who invented the air conditioning compressor as we know it?

Fittingly, it was a man from Florida who first thought of cooling the air in a room using a compressor. John Gorrie was a physician, who needed ice to keep his patients cool. Back in the 1800’s, if you needed ice, somebody had to ship it from colder regions. So if you wanted a cold drink in the summer, you needed actual Arctic ice!

That wasn’t good enough for Gorrie. The difficulty of hospital care- particularly in the 1840s, when Gorrie worked- were considerable. You couldn’t wait until the next shipment came in. But while Gorrie saw the considerable use of his idea, even imagining whole cities using centralized air conditioning, he couldn’t find financial backers. Nobody picked up the idea for another fifty years.

Finally, in 1902, Willis Carrier invented the first air conditioning unit designed for indoor cooling. He first sold the idea to businesses that needed to control both temperature and humidity. But in the next few decades, the idea caught on, and designers began to install air conditioning units in homes around America.


The function of an air conditioning compressor

The compressor is absolutely vital to any air conditioning unit. Without a compressor, or a fully efficient compressor, air conditioning is impossible. Why? Because the compressor sucks in the cooled refrigerant, on its way back from the indoors. It then squeezes the refrigerant, at this point a liquid, which increases both its heat and pressure.

It’s then pumped out of the compressor, and through the condenser coils. This cools it down against the outside air. As the gas cools down in the condenser coils, it turns back into a slightly cooler liquid. This liquid passes through an expansion valve, which releases this liquid into a larger pipe and therefore releases pressure from the liquid, and cools it yet further.

The evaporator coils evaporate the liquid, and draw in heat from indoors. This cycle repeats indefinitely, consistently cooling the temperature indoors and releasing the heat outside.

How does the compressor help with heat transfer?

Without the compressor, the air conditioner won’t work properly. That’s because in order for the refrigerant to alternately cool and then heat up again, it needs to be physically compressed. That increases its pressure. In science, pressure and heat are intimately linked: without going into too much detail, when pressure is increased, so is heat.

It is possible to find air conditioners that don’t use compressors. It’s also possible to find air conditioners without outside units. There are many different designs, but by far still the most common are units with compressors. The compressor is one of the few mechanical parts of the air conditioner. That’s why it often breaks down, and that’s why inventors have tried to replace its use, especially in portable units. It also consumes a lot of electricity, but in order to make heat flow against the laws of thermodynamics- from a cold place to a hot place, and not the other way round- you’ll always need to use power, anyway.


What kind of problems affect an air conditioning compressor?

Your air conditioning compressor often makes clanking noises that are the first signs of a broken air conditioner. If the intake reed valve isn’t sat properly, it can result in improper pressure levels because of gas leaking back along the system. Over time, this stops the air conditioner from being able to do its job, because the cooling mechanism relies on pressure differences.

Similarly, the discharge reed valve can allow gas to escape, and lower the pressure of the gas moving forward through the system. This lowers the efficiency of the compressor, stopping it from being able to circulate the refrigerant properly. If the air conditioning compressor fails to circulate the refrigerant properly, the process of heat transfer fails.

If your air conditioning compressor breaks down and needs to be repaired or replaced, you should contact a professional. It’s a complex job that requires a lot of expertise. But that’s fine- you can always install a more modern and efficient model while you’re at it!