Category - Air Conditioning
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Pat Kelly, Digital Marketing Manager

31 Jan : Updated 18 Apr ● 6 min read

A complete guide to air conditioning components

An air conditioning unit is a valuable piece of equipment, especially during the warmer months when our homes can be hot, if not too hot. 

Whether you're looking to purchase air conditioning for your home and want to understand how each component works, or you currently own an air conditioner and need spare parts to repair your system, you're in the right place. 

Here, we explore what each air conditioning part does, how they work, and how you can maintain them.. 

  1. Evaporator coil
  2. Filters
  3. Compressor
  4. Condenser coil
  5. Expansion valve
  6. Fan
  7. Refrigerant 

Internal air conditioning parts

Evaporator coil

What does the evaporator coil do?

The coil contains a refrigerant/Gas and essentially acts as a heat exchanger - removing heat from the indoor air and allowing the other components of the air conditioner to cool the room. 
Read our full guide on evaporator coils for more information.

How does the evaporator coil work?

When you turn your air conditioning unit on, the indoor component pulls in warm air from the room through a fan. This warm air passes over the evaporator coil and reacts with the refrigerant, which is turned into a gas and blown back into the room to cool it. It then expels the warm air outside.

How to maintain the evaporator coil

Keeping the evaporator coil clean is important to ensure it's always safe and efficient. If it is not kept clean, there is the possibility of higher energy usage and the risk of a breakdown.
If your air conditioning system is no longer blowing out cold air, it might be time to install a new evaporator coil, or you can read our expert guide on how to repair the evaporator coil.


What does the filter do?

The air conditioning system filters help clean and maintain good air quality by removing particles and pollutants that may circulate through your system.

How does the filter work?

The filters on an air conditioning unit act as a barrier - intercepting things like dust, pollen and pet hair. As well as keeping you safe from germs, the air filter also protects other parts of the air conditioning unit, like the evaporator coil.

How to maintain the filter

You should replace or, at the very least, clean the filters inside your system regularly to eliminate the build-up of debris and dust. It will also help your overall air conditioning system to run more effectively.

External air conditioning parts


What does the compressor do?

Air conditioning compressors change the state of the refrigerant in the system to cool your home.

How does the compressor work?

As the name suggests, compressors compress the refrigerant in gas form, increasing the pressure and temperature. As this gas travels through the system, the refrigerant turns back into a liquid. Once it's in the indoor unit, the refrigerant turns back into a gas, absorbs the heat from your home, and the cycle starts again.

How to maintain the compressor

You'll know if you have problems with the compressor because the cooling cycle will not work. To maintain the compressor, you should keep your system clean, including the coils and filters. You should also keep an eye on the refrigerant levels; if it's running out, this can put a strain on the compressor, affecting its performance.

Condenser coil

What does the condenser coil do?

The condenser coil removes the heat from the refrigerant before transporting it to the evaporator coil in the indoor section of the air conditioner.

How does the condenser coil work?

Once the evaporator coil absorbs indoor heat, the refrigerant travels to the condenser coil - at this point, the refrigerant is hot. Once the refrigerant reaches the condenser coil, the hot air is released outdoors. 

Next, a fan in the outdoor section of the unit pulls outdoor air across the condenser coil - helping to remove the heat from the refrigerant and changing it back to a liquid.

How to maintain the condenser coil

As the condenser coil sits in the part of the air conditioner that lives outside the home, you must keep the outdoor unit free of obstructions, like leaves and branches, that can disrupt the airflow. Additionally, you should have the whole air conditioning unit serviced regularly to ensure it's in good working order and that you can detect any issues before they get worse. 

Expansion valve

What does the expansion valve do?

The air conditioning expansion valve has been designed to remove pressure from the refrigerant that has been built up by the compressor. The valve 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.

How does the expansion valve work?

The expansion valve helps to control the flow of the high-pressure refrigerant into the low-pressure evaporator coil. This pressure drop cools the refrigerant, which absorbs hot air through the evaporator coil, cooling the air.

How to maintain the expansion valve

You should undertake regular visual inspections of the whole AC system, including the expansion valve, to spot any signs of damage, leaks or corrosion. If you do notice any damage, you should contact a qualified HVAC technician to take a look. 


What does the fan do? 

The fan can be found in the outdoor unit; its main job is to release the heat from your home from the condenser coil.

How does the fan work?

As the refrigerant releases heat to the condenser coil, the fan blows outdoor air over the coil, helping to cool the refrigerant. The fan is crucial to the air conditioner's efficiency, as it operates in conjunction with other key components, like the condenser coil and compressor.

How to maintain the fan

Ensuring the fan is clear and undertaking visual inspections before use will ensure the smooth running of the unit. If the fan breaks or one of its blades becomes damaged, you may hear a clunking sound, so keep an ear out for any unusual noises if you suspect something is wrong. You should also wipe the blades regularly to avoid the build-up of any dust on them. 


What does the refrigerant do?

Air conditioning refrigerant passes through the entire system as the different components do their jobs.

How does the refrigerant work?

The refrigerant works in both liquid and gas forms and works to absorb heat before converting it into cool air as it passes through the system.

How to maintain the refrigerant

It is good practice to check for refrigerant leaks before and after you use your air conditioner. The signs of a leak include: 

  • Warm air and low airflow
  • Increase in electricity bills - this may indicate your system is having to work much harder than normal
  • Noisy system

If you spot a leak, you should contact an HVAC technician immediately. 

Beat the heat

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Choose an air conditioning unit from BOXT

If you're fed up with struggling to sleep and having to listen to a fan whirring all day, air conditioning could be for you. At BOXT, we stock a full range of leading manufacturers and could fit your new system as early as tomorrow.

Unsure what sort of system you need? Don't worry; our Find an AC service will do all the work for you. Simply answer a few questions about your home, and we'll recommend systems from leading brands. So you can pick the price most suitable for your budget. 

Alternatively, you can check out the air conditioning guides on our website. Here, we provide tips and advice on selecting, replacing and maintaining your air conditioning unit


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