air conditioner located outside in yard next to white house

How Does an Air Conditioner Work?

We all love the benefits of an air conditioner blowing cool air on us on hot Summer days. If you are like me, you probably always thought air conditioners took warm air from outside, turned it into cool air, and then delivered that cool air indoors. This seemed like the most logical, common-sense way for an air conditioner to work. But, now I know that is not how they work. As a matter of fact, their operation is quite the opposite.

Then How Do They Work?

When your air conditioner starts up, it is triggered by the current thermostat setting you have the thermostat set to. Your thermostat sends a signal to the ac unit’s circuit board requesting cool air. The circuit board turns on the blower motor which is located in the home or business (where the furnace/air handler is). At this time the fan and compressor located in the condenser unit (outside unit) also fires up. We’re getting started!

From here refrigerant in the lines is transferred back and forth between the evaporator coil which is located inside (where the furnace/air handler is) and the condenser coil (outside unit). During this process the blower motor located in your furnace or air handler is pulling in warm air from inside via the return vents. This warm air passes over the cold liquid refrigerant in the evaporator coil. The cold refrigerant absorbs the warm air that came from inside the home or business and is now in gas form because of the heat. This warm gaseous refrigerant continues it’s journey to the outside condenser unit.

Once the warm gaseous refrigerant reaches the outdoor unit, it is compressed and pressurized in the compressor. This gaseous refrigerant is even warmer now and enters the condenser coil where it releases its heat to the air blowing over it via the fan. This warm air is blown to the outside environment. Now that the once warm gaseous refrigerant has released its heat, it has condensed and is back in its cool liquid form. This cooled liquid refrigerant is sent back indoors to the evaporator coil to absorb more heat and to repeat the process.

Now you are probably wondering where the cool air that is delivered inside comes from. Well, the blower that sucks in the warm air from inside and blows that warm air over the evaporator coil is also delivering the cool air inside. See, as the blower sends the warm air over the evaporator coil and the warmth is removed, the remaining air, which is now cool, is delivered by the blower to the supply vents via the air ducts. The supply vents is where the cool air comes out into your home or business providing that magical cooling experience.

The image below should help you further grasp how an air conditioner works. The process begins with warm air being pulled in by the blower through the return vent.

colored diagram describing how an air conditioner works

Was that a lot to take in? Let’s go over a couple of components which should help paint a clearer picture in your mind.

Evaporator Coil vs Condenser Coil

Remember, the evaporator coil is always located inside with the furnace or air handler. The furnace or air handler is what contains the blower motor which pulls in the warm air from inside and also disperses the cooled air inside. The evaporator coil contains cool refrigerant that absorbs the heat from the warm inside air. Here the refrigerant is turned into a gas.

The gas refrigerant is then transferred to the condenser unit located outside. This gas refrigerant is compressed and transferred to the condenser coil. Here, the gas refrigerant releases it’s heat to the air blowing over it via the fan and condenses. It is then back into it’s liquid form. This whole process is then repeated.

So in the evaporator coil the refrigerant gains heat from the warm air. In the condenser coils the refrigerant loses heat.

So, as you can see, the process is a heat transferring process.

The Blower Motor

It’s important to understand the simultaneous activity of the blower motor (or blower). Imagine a fan that sucks in air and then blows that air out of the other side. Well, this is all a blower is. It is simply pulling in the indoor air through the return vent and then blowing that same air through the ducts to the supply vents. The only difference is that an evaporator coil is installed between the blower and the supply vents. So, all of the air being blown or delivered to the supply vents has had any heat that was in it removed. Now all that remains is cool air. And that cool air is what we get coming out of the supply vents and into our homes and businesses. You can see this process clearly in our previous image above.

In a Nutshell

As I mentioned at the beginning of this post, air conditioners don’t work as most of us imagined they would. Rather than transforming the outside warm air into cool air, they actually transform the inside warm air into cool air. This is accomplished through a heat transfer process by simply removing the heat from the inside air and delivering the remaining cool air back inside via the supply vents.

I don’t know if you have noticed it or not, but we have gone over the air conditioning process 3 times now. Each time has been in a less detailed way. This should have provided a “few coats of paint” to help you soak this process in.

I hope this has given you a clear understanding of how air conditioners work. This understanding will help you understand how your own air conditioner works and you’ll have more insight when it comes to troubleshooting your own system.

Did you have the typical (incorrect) understanding of how air conditioners work? Please share any comments or questions you might have!

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