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BUYER GUIDE: Split-System Air Conditioning

BUYER GUIDE: Split-System Air Conditioning

Last edited: 7th September 2023

Split-type air conditioning systems come in a variety of different shapes and sizes to suit most applications and budgets. The key thing to remember when looking to purchase any split-type air conditioning system is that you will need to employ the services on an F-GAS registered engineer to carry out the installation (should you need assistance to locate an engineer in your area, we use a vast network of engineers in the UK, so please get in touch)

The type of split type systems available include:

Your room type and where you wish to have the system installed within the room will impact the overall choice you make.

A single split system will consist of one indoor unit and one outdoor unit, which is then connected via two refrigeration pipes and an electrical cable. The indoor unit will also have an extra pipe coming from it which is used to drain the condensate generated from the system when operating in cooling mode.

It will also require a power supply to the outdoor unit, which will usually require the services of an electrician (unless your F-GAS registered engineer is multi-qualified, so speak to them first).

Modern technology has allowed for air conditioning systems to no longer only produce cool air but also work in reverse cycle and become an excellent source of heating too! Most split systems have this capability now, but it’s always worth double checking and reading the manufacturers description thoroughly, if this is a feature you are looking to benefit from.

No matter which system you choose to have installed, all systems must be sized correctly for the room they will be used within. Failing to do so can lead to shorter system life spans, increased energy consumption or incorrect temperatures values. Systems are usually rated in either kW (KiloWatt) or BTU (British Thermal Unit) depending on the manufacturer.

To aid you in selecting the best system for your room size, we have created the below chart to be used as a guide for reference (having a site survey from a qualified professional is the best way to get an accurately sized system):

Power Output 

Room Size (up to) (approx)



Square metres (m²)

Square foot (ft²)

















































Easy-Fit Systems

Although these systems are categorised as ‘Easy-Fit’ they are still a split-type system, which means they must still installed with respect to FGAS legislation. They are named ‘Easy-Fit’ as they come with a designated length of pipework (usually copper pipes) and lagging and can be semi self installed, but MUST still be commissioned by an FGAS registered engineer (they are not a fully DIY product).

The systems in the Easy-Fit category shown on our website are a very popular choice, as you get a high spec system with a brand name compressor for a very low price point.

High Wall Mounted Systems

The most popular choice for residential applications! The majority of consumers wishing to purchase a system for a residential property opt for a high wall system as these don’t take any up any valuable or useable floor space and are installed towards the ceiling height, so are often out of your eye line.

These are available from numerous manufacturers with most choosing white as their main indoor unit colour and offering numerous options for upgrades from Alternative Colours, Wi-Fi and Smart Control to Advanced Air Filtration and Bacteria Killing technologies.

Most units will be rectangular in orientation, with exception of the LG Artcool Gallery which is unique in design and made for those that want air conditioning, without the look of a conventional air conditioner.

Because of the popularity of high wall systems they are the most mass produced by manufacturers, making them the cheapest of the installed system to purchase. Obviously, the price will be dependent on the brand name (some just are more expensive than others) but will overall be depicted by the choice of technology level you wish to select (the more technology you want, the higher the price point will be).

Also, larger systems will cost more than smaller systems because of the extra parts being used to manufacture the systems and the extra refrigerant that is used to make the system operate.

Low Wall (Console) Systems

Often used by people wishing to have a system installed into a conservatory or within an attic space with limited wall height space. They offer an alternative solution to a high wall system but have the same requirements in terms of installation.

Because they are not as widely used as high wall mounted options, the systems are often more expensive to purchase and rarely include the same advanced features  as a high wall option.

Ducted Systems

For those people that want air conditioning but don’t want to have a unit on show within a room, a ducted system can be used, so the only part usually shown is a grill or vent. These are a great solution for a discreet cooling/heating option but can be more expensive than a wall mounted system.

You will also require the services of a ducting company to install the required duct work within the premises these are to be used, as the majority of air conditioning engineers don’t undertake this part of the installation.

Ceiling Cassette Systems

Ceiling cassette systems are most regularly used within commercial premises like shops and office buildings with suspended ceilings, as the units are often quite large and bulky.

The systems capability in power output is often available in a far larger size than alternative single split options, making them even more suitable for the commercial market.


As mentioned above, all split-type systems installed within the UK will need to be either full installed or at a minimum, commissioned by an F-GAS registered engineer. Because of this, often people are put off from purchasing because of the additional cost of having a trained professional carry out the job. However, by having the system installed correctly, not only do you get peace of mind that the system will operate as it should, but you will usually get 12 months workmanship warranty on top of the manufacturer’s warranty period.

Installation costs will vary depending on which type of system you choose to go with and this is for numerous reasons involved with the installation process. A high wall system installation may be possible by just one installer and could be as simple as drilling 1 hole through the wall, whereas installing a ceiling cassette may involve numerous installers, with scaffolding, condensate pumps and additional extras. Just the same as installing a ducted system will often involve the use of another trade (in the form of a duct worker) and these additional factors will influence the overall cost of an installation.


The majority of systems come with the ability to be used in various functions, such as;

Cooling – System produces cooled air only

Heating – System produces heated air only

Auto – System cycles between cooling and heating functions

Dehumidifier/Dry – System works as a dehumidifier, drying the air only

Fan Only – System operates solely as a fan, not giving cooled, heated or dried air

When using the system in the warmer months for cooling, it is better to use the Cooling function and likewise in the cooler months, it is better to use the Heating function, rather than using Auto function. This is because using Auto mode cycles the systems function between cooling and heating and when switching from one to the other, the system has to stop, reset and restart, which can cause a differential in temperature and is not an instant change (it may take anywhere from 2 to 15 minutes to change from one mode to the other, depending on conditions and manufacturer specifications/programming).

Smart Capability/Wi-Fi

On top of the basic functions, paying the extra to get a system with WiFi capability is well worth the extra cost as it gives you the ability to control the system remotely, from anywhere, as long as you have an internet connection.

You may be wondering why you would want to take control of your system when you aren’t there to use it or feel the benefits?

Well, imagine a scorching hot day and you’re just about to finish work, knowing you’ve got a 30 minute commute and you’re going to walk into your home, where the sun has been pouring through the windows all day and turning your evening respite at home into a furnace...

Now imagine having an air conditioning system installed in your property, that you can turn on before you start your 30 minute commute, so when you walk into your home and it’s scorching like the surface of the sun outside, the inside is already cooled as if it were a penguin’s food store...Doesn’t that sound more appealing?

You also usually get better timer settings with use of the manufacturer’s app (as long as you have a smart phone/device) so you can set the system to come on and go off, should you forget to do so yourself.


Due to the advancement of modern technology, almost all split type systems on the market nowadays are equipped with inverter technology compressors. This means that no longer does the system turn on with a massive draw in current and then continue to do this every time the temperature is reached and the system turns itself off, causing a huge amount of inefficiency and costing a small fortune for continued use (like the air conditioning systems of old). Now, when systems are operating and reach a desired temperature, instead of switching off then wind done and ‘tick over’ staying ready to build and increase power again when needed, but without having the big current draw to go with this cycle.

This information means that air conditioning is able to achieve efficiency levels never known previously in the industry, with some systems even achieving A+++ ratings!

Noise Level

The loudest part of any air conditioning system is the compressor, but as a split system has the compressor housed inside the outdoor unit, this means that the indoor unit is often very quiet. The size of the system will also dictate the noise level the system will produce, with smaller power output rated systems producing quieter operational results than larger sized systems.

Most indoor units of 2.5kW or 3.5kW systems are rated from around 22 dB in low fan speed, getting louder as the fan speed increases. As quiet as 22 dB is (similar sound level to a ticking watch), if this is still too loud for you, then you could opt for an LG system as on their 2.5kW and 3.5kW ranges go as low as just 19 dB when using ‘Sleep’ mode (it also lowers the outdoor unit noise level by 3 dB too).

The outdoor units for the majority of manufacturers will sit somewhere around the 48-50 db level when measured with Sound Pressure and approximately 65 dB when measured using Sound Power

Air Treatment/Filtration

All air conditioning systems (and even most portable units) will have fine mesh filters covering the evaporator within the casing of the indoor unit. These filters are designed to filter out dust particles and other foreign bodies from the air, aiding to keep the inside of the unit as clean as possible (which aids efficiency performance levels) and also cleans the air as it passes through the unit, improving overall air quality.

If having a system that produces extremely efficient cooling and heating, while filtering the air even further is what you desire, then you can purchase systems with even higher levels of technology to do exactly this. Many systems towards the top end of the market now incorporate various extra features, such as;

Internal UV lighting - designed to kill bacteria in the air.

Auto Cleaning/Washing – The internal unit will run through a process of self cleaning (sometimes during normal operation), washing and drying the unit to prevent excess moisture and harmful bacteria building up.

Ioniser Filtration – Ionisers (or negative ion generators) create a static charge around floating airborne contaminants (such as dust particles, pet dander, allergens, etc), which causes them to stick to the nearest object they come into contact with. This in essence removes them from the air circulating within the environment, aiding to keep the air cleaner.

Warranty & Servicing

All split type air conditioning systems will require regular servicing and maintenance from an FGAS registered engineer.

Depending on the environment where the components are installed, servicing requirements may be advanced or required more frequently. This could be required due to areas of high humidity (spa’s, pool houses, etc) or increased levels of dust or dirt (workshops, garages, etc) and it is best to check the manufacturers specific information or speak with your installation engineer.

Having the system serviced ensures the system continues to operate at its optimum performance and efficiency levels, but will also maintain the manufacturer’s warranty period. Warranty terms will be dictated by each manufacturer independently, so it is best to read the literature that accompanies the system after its installation for further information.