Understanding Air Conditioning Parts and Common Issues

June has been all about air conditioners, from talking about the basics and understanding energy efficiency in them. This time on the blog we’re going to keep on with that trend, further educating our readers so they can better understand how their home’s AC works as well as how to maintain it and get the best results. In keeping with that goal, let’s talk about the different air conditioning parts that make up the air conditioning unit.

Air Conditioning Parts

There are five main parts of an air conditioner to talk about: refrigerant, compressor, condenser coil, evaporator coil, and expansion valve. 


We’ve talked plenty about refrigerants before, especially the now discontinued and phased out Freon. Refrigerants are special fluids necessary to cooling the house. At certain temps the liquid changes into a vapor that is able to absorb heat from the hot air. It works something like this.

The refrigerant operates in a bit of a loop, moving through an air conditioner’s cooling tubes and copper coils that connect the inside unit to the outside unit, the refrigerant absorbs the heat from your indoor air, as it does it’s magical change from gas to liquid. After absorbing heat from the inside air, the liquid then travels to the outdoor components where the heat is ‘released.’ Following the heat dispersal, the refrigerant again turns back to its gaseous state and begins the cycle all over again! The refrigerant is made cold, the coils are cooled, a fan blows hot air over cold coils, the air is cooled and circulated.

Examples of Refrigerants


After the refrigerant we should probably talk about the compressor, how it works and what it does. Compressors pressurize the refrigerant which raises its temperature. There’s a whole bunch of science here including a number of scientific laws,  but basically when pressure rises so does temperature, so compressed refrigerant makes for warmer refrigerant. When it hits the specific temp it is now a gaseous refrigerant. Another natural law, heat flows from hotter to colder things, so heating the refrigerant to higher than the outdoor temp ‘pushes’ the refrigerant outside where it can vent the heat.

Evaporator Coil

Evaporator coils are the crucial part that actually grabs the heat from inside your house!  Made up of copper tubes, they receive the liquid refrigerant from the expansion valve (more on that later). When the warm air from inside the home is blown over the cold coils, the heat transfers (remember heat transfers from hot to cold objects) and is absorbed into the coils. The refrigerant inside the coils are warmed and turn into vapor.

Condenser Coil

This part is on the outdoor portion of the unit. The condenser is where the hot refrigerant moves to from the evaporator coils. The condenser coils are designed in such a way to allow heat to transfer from the coil to the outdoor air, with the help of a condenser fan that blows the air over the coils. The condenser coil is in the outdoor air conditioning unit. It receives the high pressure, high temperature refrigerant from the compressor. Think of it as the opposite of the evaporator coil. Whereas the evaporator coils contain cold refrigerant and absorb heat, the condenser coils contain hot refrigerant and release the heat to the outdoors.

As the heat leaves the refrigerant to the outside air, it turns back into a liquid where it then flows to the expansion valve for the next leg of the journey!

A Coil Close-up!

Expansion Valve

When the refrigerant leaves the condenser while still liquid, it has dispersed some heat, but it is still too hot to go into the evaporator coils yet. It needs to cool down and that’s where the expansion valve jumps in. The expansion valve decreases the pressure  which in turn cools down the gas (remember the science we mentioned earlier about pressure and temperature). With the pressure off, the refrigerant cools down enough to move on.

Have Problems?

Now you know all the different parts of your HVAC system, you may have a better idea of exactly how they are supposed to work. But we know better than anyone that things can go wrong, refrigerants might run out or coils aren’t releasing heat like they’re supposed to. So what are you to do? That’s simple. Give ACE Home Services a call today and schedule your service today!