Multi-Split Air Conditioners

Cool and heat several rooms from a single outdoor unit with our range of Multi-Split Air Conditioners, built for homes and workplaces that need more than one zone of climate control without cluttering an exterior wall with multiple condensers.

Please note: We are legally required to verify your F-Gas certification before supplying restricted refrigerants. Orders without valid certification will not be processed. Form can be found via F-Gas certification form link

What is a multi-split system?

A multi-split system connects one outdoor condensing unit to two or more indoor units, typically wall-mounted, though cassette, ducted and console indoor units can often be mixed on the same outdoor unit depending on manufacturer compatibility. Each indoor unit is controlled independently, so a bedroom can run at a different temperature and schedule to a living room or office, all from the same outdoor box.

This differs from a single-split system, which pairs one indoor unit with one dedicated outdoor unit and suits a single room. It also differs from larger VRF/VRV systems, which serve many zones across commercial buildings and require a more complex design process than domestic multi-split. If you're cooling or heating just one room, our Split Air Conditioners collection covers single-split units.

Most domestic multi-split systems are reverse-cycle air-to-air heat pumps, so they provide both cooling in summer and efficient supplementary heating in winter, alongside dehumidification for damp shoulder seasons.

How multi-split systems are sized

Getting the sizing right on a multi-split system is less straightforward than a single split, because one outdoor unit has to support several indoor units running simultaneously.

Indoor units are sized to the room, the same way as single-split — floor area, ceiling height, glazing and orientation, and occupancy all matter, with south- and west-facing rooms typically needing more capacity.
The outdoor unit is sized using diversity, not a simple sum of the indoor units. Manufacturers generally rate the outdoor unit to cover somewhere between 80–100% of the combined indoor capacity, on the basis that every zone is rarely calling for full output at the same time. A pair of 2.5kW indoor units, for example, doesn't necessarily need a 5.0kW outdoor unit — check the specific manufacturer's combination chart rather than assuming a straight total.
Head count is capped per outdoor unit. Most residential multi-split ranges support 2–5 indoor units per outdoor condenser; beyond that, a second outdoor unit or a commercial VRF system is usually the better fit.
Pipe runs and height differences are limited. Total equivalent pipe length and the height difference between indoor and outdoor units are both capped by the manufacturer, commonly in the region of 100–120m of pipe run and up to a 15–30m height difference across the longest circuit — relevant for multi-storey installs or outdoor units sited some distance from the property.

Common specification errors

Assuming outdoor capacity = sum of indoor capacities. As above, this usually results in an oversized (and more expensive) outdoor unit. Manufacturer combination charts account for diversity.
Mixing indoor unit types without checking compatibility. Wall, cassette, ducted and console units can often share an outdoor unit, but not in every combination — confirm against the specific outdoor unit's compatibility matrix before ordering.
Ignoring R32 refrigerant charge limits in small rooms. Where a system uses R32 (an A2L mildly flammable refrigerant), total system charge needs to stay within limits relative to the smallest served room's volume. This is rarely an issue for typical UK bedrooms and living rooms, but is worth checking on larger multi-split systems feeding smaller ensuite or utility spaces.
Treating multi-split as a DIY-friendly upgrade over single-split. The refrigerant pipework, vacuum/pressure testing and F-Gas handling requirements are the same as single-split — installation and commissioning must be carried out by an F-Gas certified engineer.

Choosing multi-split vs single-split

One room only: a single-split unit is simpler and usually cheaper — see our Split Air Conditioners range.
Two to five rooms, one property: multi-split keeps the outside of the building tidy with a single outdoor unit and lets each room run independently.
Six or more zones, or a commercial/multi-tenant building: likely better served by multiple outdoor units or a VRF system — request a custom quote and our team can advise on system design.