Multi-split air conditioning

How a multi-split works

A multi-split system has one outdoor unit connected to two or more indoor units, each in a different room. Every indoor unit has its own pair of refrigerant pipes back to the outdoor unit and its own controller, so you can set each room to the temperature you want and switch rooms off when they are empty. The outdoor unit adjusts its output to match the rooms that are running.

On most multi-split systems, all the indoor units need to be in the same mode at the same time, all cooling or all heating. In a home that is rarely a problem. In a building where some rooms need heat while others need cooling, a VRF heat recovery system is the better fit.

Multi-split or several single splits?

For two or more rooms you have a choice: one multi-split, or a separate single split for each room. Each has its strengths.

• Multi-split: one outdoor unit instead of several, which matters when wall space is tight, appearance is important or neighbours are close. One electrical supply instead of several.
• Single splits: if one system fails, the others keep working. Pipe runs can be shorter where each room has an outside wall nearby. Adding a room later is simple.

A multi-split outdoor unit is larger than a single split unit, and if it fails, every room it serves stops. We weigh up the layout, the pipe routes and how you use the rooms and recommend whichever is better for your property. Our guide on whether multi-split is right for your home covers this in more depth.

How many rooms one outdoor unit can serve

Each manufacturer makes multi-split outdoor units for a set number of indoor units, with a limit on the total output they can connect and on the length of pipe to each room. Our domestic multi-split pricing covers two to five rooms. Beyond that, or for very long pipe runs, the answer is usually two outdoor units or a VRF system. We check the manufacturer’s limits for your layout at the design stage, so every room gets the output it needs.

Mixing indoor unit types

One of the advantages of a multi-split is that the rooms don’t all need the same kind of indoor unit. Depending on the manufacturer and model, you might have wall-mounted units in the bedrooms, a floor console in a room with a sloping ceiling, a ducted unit hidden in the ceiling of the living room and a cassette in a kitchen with a suspended ceiling. We check that the units you want are compatible with the outdoor unit and size each one for its room. Our article on indoor unit types shows the options.

Pipe routes and the outdoor unit

The pipework is the part of a multi-split that takes the most planning. Each indoor unit needs its own pipes and drain, and they all run back to the outdoor unit. We look for routes through lofts, ceiling voids, cupboards and along outside walls in trunking, and we agree them with you on the survey so there are no surprises on installation day.

The outdoor unit needs good airflow, a firm base or brackets and a position that keeps noise away from bedrooms and neighbours. We also check the charge of refrigerant the system will hold. Larger systems may cross the threshold for periodic F-gas leak checks, which we explain on the quote.

Price, VAT and installation time

A two-room multi-split is typically £2,800–£4,500 + VAT, and three to five rooms £4,500–£8,500 + VAT. Prices include supply, installation, commissioning and F-Gas documentation. The number and type of indoor units, the pipe lengths, access and any electrical work affect where your job sits in the range. Installation usually takes more than one day, and we tell you how long on the quote.

HMRC zero-rates energy-saving materials installed in homes until 31 March 2027, and says most air conditioning units are air source heat pumps, although each case depends on the facts (HMRC Notice 708/6). We confirm the VAT on your quote. This is general information, not tax advice.

Servicing a multi-split

A multi-split needs the same care as several single splits. Each indoor unit has its own filter, coil, fan and condensate drain, and they all need cleaning and checking. The outdoor unit serves every room, so keeping its coil clean and its airflow clear matters even more than on a single split. On an annual service we clean and check every indoor unit, check the outdoor unit and its electrics, measure the system’s pressures and temperatures and look for signs of leaks. Between visits, cleaning the filters every few weeks in heavy use keeps every room working well.

Brands and warranty

We install multi-split systems from Mitsubishi Electric, Daikin, Fujitsu, Panasonic, Toshiba, LG, Samsung, Mitsubishi Heavy Industries and Hitachi. Each brand has its own range of outdoor units and compatible indoor units, and we recommend the one that fits your rooms best. Warranty is the manufacturer’s, on its own terms, which we set out on your quote. An annual service covers every indoor unit and the outdoor unit in one visit.