Category - Air Conditioning
Guide author photo

Will Scholfield, Engineer

31 Jan : Updated 24 Oct ● 4 min read

What is an indoor air conditioner & how do they work


Summer brings all the things we love - barbecues, the beach, picnics and outdoor swimming.  The heat seems beautiful when you are sitting outside with a cool breeze, a cold drink and some shade, but when you go inside and your home feels like a greenhouse, you struggle to sleep, and you’re sweating all of the time, it’s a different story. 

Today’s modern cooling systems are developed so that you never have to feel hot and sticky in your own home again. Not only are they good for regulating the temperatures throughout your home - they have added health benefits too. Have you ever considered installing an indoor air conditioner? Are you a little confused about how they work? BOXT have designed this guide to help you. So, let’s get into what they are and how they work.  

What is an indoor air conditioner? 

Most air conditioners have a main air con unit indoors and an outdoor unit that connects to this. The indoor unit's primary purpose is to circulate the cool air, and it works with the outdoor unit to do this. The indoor unit should be mounted to a wall in a high level position. 

An indoor air conditioner contains the evaporator coil and a filter. The outdoor unit has the fan, a condensing coil and a compressor. Both of the units are required to work together to provide cool air to the rooms of your home. 

What are the different parts of an air conditioner? 

An air conditioning system usually contains the following:

  • a thermostat to control the system
  • an indoor unit that contains both the evaporator coil and fan to circulate the cool air
  • an outdoor unit that contains the fan, the condenser coil and the compressor
  • a copper pipe that allows the refrigerant to flow between the indoor and outdoor units
  • a duct for air to circulate from the indoor unit out through the house and back to the indoor unit 
  • an expansion valve that regulates the amount of refrigerant going into the evaporator coil 

So, how does it work then? 

Air conditioning works by removing the heat and humidity and providing cool air in exchange. It’s a lot different to a fan which simply circulates the hot air throughout your home. The air conditioning unit takes the heat and humidity and deposits it outside, returning the cool air to your home, using a specialist chemical called a refrigerant. 

Throughout the process the refrigerant is converted from gas to liquid and back again. 


The compressor raises the pressure and sends the refrigerant gas to the condenser coil where it is converted to a liquid. 


The refrigerant returns to the indoor unit and enters the evaporator coil. It then evaporates, cooling the indoor coil. 


The fan then blows the indoor air across the cold evaporator coil where the heat from your home is absorbed into the refrigerant. The cool air is then circulated throughout the room. 

And finally...

The heated air is sent back outside to the compressor. This cycle continues until your home reaches the desired temperature. 

What is the most popular indoor air conditioning system?

The most popular air conditioning system is the split system air conditioner. This system can be worked by a remote control and often has the option to be fitted with a heating pump facility for all year comfort. 

What are the health benefits of an indoor air conditioning system?

Air conditioning systems purify the air and catch airborne dust, bacteria, microbes and fungi. They also remove airborne allergens, reducing asthma attacks and hay fever. Air conditioners also help reduce the risk of dehydration and heatstroke. If you are looking for a bedroom air conditioning solution, they are quiet and do not interrupt your sleep so you won't be sleep deprived like you can be when using a fan. 

Get a quote from BOXT today.

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