Top Components of Air Conditioning Systems and Their Functions (2024)

The world is such a huge place, and because of this, weather conditions are going to vary from one place to another. There are some places that are more familiar to coldness, but then, on the flip side, there are also some places that are prone to the sweltering heat. For places like that, people living there would naturally want to find a way to combat the heat so that they would be able to go on about their lives comfortably. And luckily, there is a way to combat the heat — and that is in the form of an air conditioner.

Table of Contents hide

1 What Is an Air Conditioner?

2 What Are the Main Components of an Air Conditioner?

2.1 Refrigerant

2.2 Compressor

2.3 Condenser Coil

2.4 Expansion Valve

2.5 Evaporator Coil

3 How Does the Refrigeration Cycle Work?

4 Takeaway

What Is an Air Conditioner?

Simply put, an air conditioner is a system or a machine that treats the air in a defined, usually enclosed area via a refrigeration cycle in which warm air is removed and replaced with cooler air. Because of the nature of the air conditioner, it is actually very similar to another HVACR appliance — the refrigerator. The only difference between the two is that air conditioners don’t have the exterior housing a refrigerator relies on to insulate its cold box. Instead, the walls in a building keep the cold air in and hot air out.

More often than not, air conditioners are installed for the sole purpose of providing comfort to people inside a particular building. But aside from comfort applications, air conditioners can also be used for process applications. Process applications aim to provide a suitable environment for an industrial or a commercial process, regardless of internal heat loads and external weather conditions. Although process applications are similar to comfort applications in terms of comfort range, it is the requirements of the process that determines the conditions, not human preference. A few notable examples of process applications include hospital operating rooms, cleanroom, facilities for breeding laboratory animals, nuclear facilities, and aircraft air conditioning.

Related Article: Top Components in a Refrigeration System

What Are the Main Components of an Air Conditioner?

As an HVAC professional, it is your job to provide air conditioners and other related services to those who need it. But before you could do that, you must first know about the five main parts that comprise an air conditioner. This is because you will be able to understand better how an air conditioner works once you know about the basic components of the system. To help you in this endeavor, here are the five main components of an air conditioner.

Related Article: Heating Systems: Types and Components


The refrigerant, also known as a coolant, is a special fluid that is integral to the cooling and freezing technology. The refrigerant operates on a closed-loop and carries heat from the inside of the building to the outside. In a way, the refrigerant is almost like a messenger or a traveler, and it is used primarily because it changes states from liquid to vapor at convenient temperatures for the refrigeration cycle.

The refrigerant moves through an air conditioner’s cooling tubes and copper coils, thus connecting the inside unit to the outside unit. Then, it absorbs heat from the building’s indoor air, changing states from gas to liquid. After absorbing heat from the inside air, the refrigerant then travels to the outdoor unit where heat is pushed outside.

Once the refrigerant has dispersed the heat outside, it changes back to its gaseous state and travels back inside. Once the refrigerant gets cold again, an indoor fan blows air over the cold coils and then circulates cold air through the building.


The compressor is the air conditioner component that pressurizes the refrigerant, thus raising its temperature. According to the combined gas law (a combination of Boyle’s Law, Charles’ Law, and Gay-Lussac’s Law), if the pressure increases, then so does its temperature. As a result, when the refrigerant is compressed, it will heat up by squeezing the gas very tightly together.

The refrigerant is heated up in order to get its temperature higher than the outdoor temperature. This is because heat naturally flows from a hotter body to a colder body, and so, in order to dispense heat outdoors, the refrigerant must be hotter than the air outside. Hence, that is why the compressor is incredibly important for air conditioners — because its primary job is to increase the pressure and temperature of the refrigerant.

Condenser Coil

The condenser coil is in the outdoor air conditioning unit, and its primary task is to receive the high-pressure and high-temperature refrigerant from the compressor. The condenser coils are designed to facilitate heat transfer to the outdoor air. The refrigerant releases heat energy with the help of the condenser fan, which blows air over the coils. Then, as the heat leaves the refrigerant to the outside environment, it turns back into a liquid where it will then flow to the expansion valve.

Expansion Valve

When the refrigerant leaves the condenser in its liquid state, it has already dispersed heat, but it is still too hot to enter the evaporator coils. And so, before the refrigerant passes into the evaporator coils, it has to be cooled down first. This is where the expansion valve, also known as a metering device, comes in.

Following the principles behind the combined gas law once more, which states that when pressure decreases so does the temperature, it is the job of the expansion valve to depressurize the refrigerant and cool it down. The way the expansion valve operates is that it removes pressure from the liquid refrigerant, thus allowing for the refrigerant to change from a liquid to a vapor or gas in the evaporator. In addition to this, the expansion valve is also the one responsible for controlling the amount of refrigerant or voltage flow entering the evaporator.

Evaporator Coil

The fifth — and definitely not the least — component of an air conditioner is the evaporator coil. And this is the component where the air conditioner actually picks up the heat from inside the building. Because of this, the evaporator coil is considered the opposite of the condenser coil: whereas condenser coils contain the hot refrigerant, evaporator coils contain the cold refrigerant.

The way the evaporator coil works is that the copper tubes receive the depressurized liquid refrigerant from the expansion valve. Then, when the indoor air blows over the cold coils, the heat from inside the building gets absorbed. As the refrigerant absorbs heat from the indoor air, it then begins to evaporate to form a vapor.

Just like how the condenser coils need the help of the condenser fan to facilitate heat transfer, the evaporator coils also need the indoor air handler’s fan — also known as the blower — to blow air over the coils.

How Does the Refrigeration Cycle Work?

Simply put, the air conditioner operates on the refrigeration cycle. The refrigeration cycle begins with the return vents, which are located inside the house, sucking in hot air from inside the room or building. Then the refrigerant picks up the heat as air flows over the evaporator coils, which are very cold.

Once the refrigerant absorbs a certain amount of heat from the indoor air, it then discharges it to the compressor, which pressurizes and heats up the refrigerant. After passing through the compressor, the refrigerant flows through the condenser coils. A big and usually loud condenser fan helps push air over the condenser coils in order to facilitate heat transfer outdoors.

After all of this has occurred, the refrigerant then cycles back over an expansion valve, depressurizing it and cooling it down. And finally, it will perform the same heat absorption process over and over again as long as the air conditioner is operating.

Related Article: Top Components in a Ventilation System


Air conditioners are some of the most incredibly important appliances in this day and age. And this is not a surprise at all: after all, a lot of places experience extreme weather conditions, and an air conditioner can help alleviate these conditions — especially the extreme heat — by cooling the air inside the building.

Because of the undeniable importance of air conditioners, HVAC professionals like you have to be ready to provide for those people who need this kind of HVAC system. But before you can do that, you must first know all about the important components that make up an air conditioner. That way, you’ll understand better just how exactly this HVAC system works, thus allowing you to improve your service to your customers.

The first thing you should know is the five primary components of an air conditioner. These primary components are the refrigerant, compressor, condenser coils, expansion valve, and evaporator coils. Then after knowing the primary components, you must educate yourself on what these components do. In other words, you must know what the components contribute to the overall refrigeration cycle, which is the process that an air conditioner operates on.

Simply put, the refrigerant is the one that picks up heat from the inside of the building. Then the compressor pressurizes the refrigerant so as to raise its temperature before the condenser coil picks up the high-pressure and high-temperature refrigerant. Once in the condenser coils, the refrigerant releases heat energy with the aid of the condenser fan. It turns back into a liquid where it flows to the expansion valve, which depressurizes the refrigerant and cools it down, and then into the evaporator coil. This whole process repeats itself as often as needed when the air conditioner is turned on.

So now that you are aware of the components and the refrigeration cycle, you should be able to use this knowledge to enrich your own service to your customers. You will now be able to provide the best air conditioners possible, and you will also be able to help your customers when they will be experiencing air conditioner troubles.


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Danny Lu

Danny appreciates how the HVACR industry has improved living conditions currently. From HVACR products being innovated to be eco-friendlier, more efficient, and using technology to self-operated using timers and sensors. He is sharing his perceptions with the HVACR industry to ensure new initiatives are available in the marketplace that would best serve the community. If want to write about HVAC industry, click here

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Top Components of Air Conditioning Systems and Their Functions (2024)


Top Components of Air Conditioning Systems and Their Functions? ›

A standard air conditioner or cooling system uses a specialized chemical called refrigerant, and has three main mechanical components: a compressor, a condenser coil and an evaporator coil. These components work together to quickly convert the refrigerant from gas to liquid and back again.

What are the major components of an air conditioning systems? ›

The six main air conditioning components that homeowners should be aware of are the thermostat, air blowing unit, air filter evaporator, condenser coil, and compressor.

What are the 4 main components in a residential air conditioner system? ›

Following the main functions of your air conditioner, the next vital thing to learn about are the main components. To simplify, there are four main parts that are essential to learn about: condenser, compressor, the evaporator, and lastly, the expansion valve.

What is the most important component of an air conditioner? ›

Compressor. Also known as the “heart” of an HVAC system, the compressor pumps refrigerant through the entire system. You'd know a compressor is broken or damaged if the air blowing into your house is hot. That can mean the compressor is not pumping enough refrigerant through the HVAC system.

What is the most important part of the HVAC system? ›

The heat exchanger is the most important part of your heater or furnace, because it's the tool that heats the air. Typical, furnaces pull air in from the outside. The heat exchanger heats the air quickly, and the air is blown into your home.

What is the difference between AC and HVAC? ›

The main difference between HVAC and AC is that HVAC generally refers to the whole heating, cooling, and ventilation system of a building, while AC often refers to cooling systems. In other words, AC is part of an HVAC system.

What component controls the entire HVAC system in a house? ›

The Thermostat That Controls Your HVAC

The thermostat is often the most visible component of your HVAC system. It acts as the control center where you switch between heating and cooling systems as well as set temperatures on a weekly or seasonal basis.

What are the four 4 basic cycles of air conditioning system? ›

Principles of Refrigeration

For this reason, all air conditioners use the same cycle of compression, condensation, expansion, and evaporation in a closed circuit. The same refrigerant is used to move the heat from one area, to cool this area, and to expel this heat in another area.

What are the three functions of the air conditioning system? ›

There are three primary functions to a room Air Conditioner. First is to cool a specific area, such as a room, not an entire home. The second is to dehumidify, to remove moisture out of the air, so you're not sitting in a cold, clammy environment. The third function is to filter the air within the home.

What is the part of the AC unit in the attic called? ›

Most often, air handlers are located in the attic, basement or a dedicated closet, and may closely resemble the shape of a gas furnace. As its name suggests, an air handler “handles” the air inside your home and delivers warm or cool indoor air throughout your entire home. What would we do without delivery!


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