How Air Conditioners Work



Did you know that before air conditioners were invented, people would use blocks of ice to keep cool? In fact, the very first air conditioners were measured in ‘ice power’. This told the user how much ice would achieve the same level of cooling, demonstrating how effective they were. We’ve come a long way since then.

Air conditioning was originally invented in 1902 by Willis Carrier as a humidity-busting solution for paper – not people! The innovation sought to help a New York publishing house solve its printing issues caused by heat and humidity which led to its paper expanding and ink smudging. As a result, the invention created a stable environment and the start of a cool-air revolution.

Back in 1914, the very first domestic air conditioner was 20 feet long, 7 feet high and 6 feet wide. As well as being large, they were also expensive. The first single-room air conditioner, invented in 1931, cost nearly £300 compared to a typical weekly wage of around £20.

Today, air conditioners are, thankfully, a lot smaller and affordable and as a consequence are commonplace in workplaces up and down the country. But how much do you know about how they work and the process that occurs inside that white box?

Here is phs Compliance’s guide which will help if you’re in the market for a new air conditioner or to help you understand your units when it comes to servicing, maintenance and repair.

What do air conditioners do?

The role of an air conditioner is to cool the air within a room. While they are most popular in the warmer summer months, they’re used year round to prevent workplaces becoming hot and stuffy particularly those without high levels of natural ventilation such as doors and windows. They can make workplaces feel fresher and more comfortable to work in. Before air conditioners were invented, businesses and schools would slow down or take holidays when it became too hot.

How do air conditioners cool air?

Throughout the conditioning process, warm air from a room is cooled within the unit and blown back out, gradually reducing the temperature in a room.

The process:

  • The air conditioner draws air into the indoor unit and runs it over evaportor coils which contain coolant fluid, constantly circulating throughout the unit.
  • As the coolant is cooler than the air, it absorbs heat and lowers the temperature of the air which is then recirculated back into the room.
  • As the coolant heats, it evaporates into a gas. Moving through the unit, it enters a compressor which increases its pressure.
  • At this point, the gas coolant travels into a condenser where heat is expelled into metal plates. The coolant condenses back into liquid form.
  • The heat from the plates is expelled outside, accelerated by fans which blow over the plates.
  • In the meantime, the coolant travels back to the front of the air conditioning unit to repeat the process and a dehumidifier removes excess moisture produced.


How can you control the temperature of an air conditioning unit?

The cooling process operates on a variable speed. When you change the temperature on your air conditioning unit, you are adjusting the motor speed which controls the process and therefore the output temperature, allowing you to maintain optimum temperature levels.

Can an air conditioners be used as heaters?

When put in heating mode, the process of heat transfer is reversed. Incoming air from within a room is warmed and returned to the room while cool air is expelled.

Do air conditioners spread coronavirus?

Ventilation is essential in mitigating the risk of COVID-19 spreading in indoor spaces. However, while air purifiers can physically remove COVID-19 particles through a filter process, these work very differently from air conditioners.

The potential risk posed by air conditioners depends completely on which type of unit you have. Split units recirculate the air within a room; drawing air in, cooling it down and blowing it back out again. There is no fresh air supply or filter. Furthermore, some air conditioners have a shared system between different rooms so could be spreading COVID-19 airborne particles around a building.

If you’re choosing between air conditioners, look out for those which have a fresh air source, and maximise the amount of fresh, outdoor air pulled into the system. The WHO also recommends that when using an air conditioning unit, open windows for a few minutes every hour to bring in fresh air from outside.[i]

What maintenance do air conditioners require?

Leak testing is required by law for air conditioning systems and components in workplaces as fluorinated gases can be contained within the refrigerant gas used for cooling. This requirement is to prevent the risk of fluorinated gases from being released into the atmosphere.

Annual leak checks are recommended for air conditioning units rated up to CO2 50 tonnes without any pre-installed leak detection system. Larger units are subject to more frequent checks. Where leak detection systems are already in pace, checks for smaller units reduce to a 24 month interval.

What do leak checks involve?

Leak testing involves the inspection of circuits and components which have a mechanical risk of leakage with an electronic gas detector, leak sprays, UV detection fluids and oxygen-free nitrogen to pressurise the circuit after the recovery of the refrigerant gas. Qualified air conditioning engineers will also record system pressures, temperatures, compressor-run currents and carry out visual inspections.

Who can service my air conditioning units?

phs Compliance has a team of expert air-conditioning engineers on hand for all your servicing needs across the country. They are experienced at routinely leak checking and inspecting units from 1.5kw to 100kw and also inspect air-handling units and Lossnay heat recovery systems.

With more than 40 combined years of experience, phs Compliance’s engineers are accredited to City and Guilds F-Gas and ODS (2079) and City and Guilds NVQ Level 2 in Air Conditioning 600/091/3 as a minimum. In addition, phs Compliance is an accredited installer with Mitsubishi Electric and fully accredited by REFCOM.


To learn more about our what Compliance offers, to get a quote, or simply to ask a query, please feel free to contact us now!

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