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What are the parts of an outdoor and indoor air conditioning unit?

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The air conditioning system has many different components, each working together to bring cool, filtered air to homes and buildings. The home air conditioner is made up of a number of different parts. Without these parts, the conditioner wouldn’t be able to work effectively, or at all. It’s important to know exactly what makes up the different air conditioning units in case they need replacing or fixing.

In this guide we’ll explain the different parts of an air conditioner in detail and how they all work together to provide cool, comfortable air for your environment.


What are the main air conditioning parts?

The most common type of home system is the split system air conditioner. This type consists of a main indoor air conditioning unit and outdoor unit that both connect together. The inside unit contains the evaporator coils and a filter, whereas the outdoor unit is home to the condensing coil, fan and compressor.

What is a refrigerant?

Air conditioning refrigerant also passes through the system as the different components do their jobs. It’s a cooling solution used in many refrigeration products and is a crucial part of ensuring your rooms stay cool.

The air conditioning refrigerant capacity can be up to 1.8 litres depending on your system. It’s always recommended to check the specifics of your system, as different air conditioning systems from different manufacturers may operate differently.

The indoor air conditioning unit.

The indoor air conditioning unit should be wall mounted, and will include the following:

The air conditioning evaporator coil.

The evaporator coil from your indoor unit will be connected to the condenser coil in your outdoor air conditioning unit. This component is the part of the air con system in which the refrigerant absorbs heat.

Evaporator coils are usually made from copper or steel, as these kinds of materials conduct heat effectively. The refrigerant sent from the air conditioning condenser coil will change from a liquid into a gas here. It will absorb the heat inside the home and send it back to the system’s condenser coil, where the process will continue in a cycle.
It’s important to keep the evaporator coil clean to ensure it’s always safe and efficient. If it is not kept clean, there is the possibility of a higher energy usage and the risk of a break down.


Filters are an essential component in any air conditioning system. They prevent dust and allergens from circulating the home and help to make the air you breathe safer and cleaner. If you didn’t have filters inside your A/C system, the air quality inside your home would be compromised.

The filters inside your system should be replaced or even cleaned regularly to get rid of the build up of debris and dust. It will also help your overall system to run more effectively.

Air conditioning ducts.

The ducts inside your air conditioning system allow air to travel through. The heated and cooled air can be pushed into or pulled out of the room through separate ducts.

In air conditioning systems, you’ll have a thermostat, enabling you to adjust the temperature of your system to one that suits you and your needs. Most modern systems also have the ability to control the thermostat remotely for even more convenience. For the ideal air conditioning thermostat setting in each room, you can adjust the temperature for more flexibility and to only cool the rooms you’re using, saving energy in the process.

The outdoor air conditioning unit.

As with the indoor air conditioning unit, the outdoor unit is home to the essential parts needed for your system to run as efficiently as it should. Here’s what your outdoor unit consists of:

Air conditioning compressor.

The compressor changes the state of the refrigerant in your system to cool your home. It compresses the refrigerant in gas form to increase its pressure and temperature. As the gas travels to the inside unit, the refrigerant changes back into a liquid by releasing this pressure and condenses back into a liquid. Once in the indoor unit, the refrigerant turns into a gas yet again and absorbs in the heat from your home. This cycle then starts again.

Problems with an air conditioning compressor will stop the cooling cycle from running, resulting in a breakdown or malfunction. It’s important that a faulty compressor is replaced as soon as possible to prevent this.

Air conditioning condenser coil.

The job of the condenser coil is to cool down the gas in its highly pressurised form. The gas, sent from the air conditioning compressor, is then changed to a liquid again. The condenser’s job is to remove the heat from the refrigerant and to transfer it to the evaporator coil in the indoor air conditioning unit.

The expansion valve.

The air conditioning expansion valve has been designed to remove pressure from the refrigerant that has been built up by the compressor. It works alongside the compressor and condenser to keep the cycle of gas and liquid going, which will cool down your home as it does so.


The fan can be found in the outdoor unit and its main job is to release the heat from your home from the condenser coil. Inside the indoor unit, you’ll have an air handling unit which helps to push cool air around the home.

The main process.

These air conditioning system components all work together to create a successful system. Here is how an air conditioning system works and the main process these components go through to bring cold air to your homes:

Refrigerant reaches the compressor as a low pressurised gas. The compressor increases the pressure of this gas, as well as its temperature.

The hot gas leaves the compressor and travels into the condenser. The condenser then removes the heat, condensing it into a liquid and lowering the temperature.

The liquid then travels through the evaporator coil, where the pressure will drop and evaporate into a gas once more.

As the refrigerant leaves the evaporator coil, it is now in a cooler, low pressure state. The fan connected to the evaporator circulates the cool air around an environment and pulls in the warmer air, releasing it through the outdoor unit.

Contact BOXT.

The components inside and outside of an air conditioning system are crucial to a perfectly functioning system. They should be kept clean and regularly monitored to make sure they’re always in top working condition. If in doubt, you should always contact a professional for advice and guidance.

If you’re looking to find the perfect air conditioning system for your home or you’d like some advice about anything mentioned in this guide, you can chat to one of our engineering professionals through our website’s live chat. Alternatively, you can use our ‘Find An A/C System’ tool for personalised recommendations in minutes.

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