Multi Split Air Conditioning Installation
One outdoor condenser drives 2–5 indoor units with independent set-points per room — perfect when external space or planning constraints rule out multiple outdoor boxes.
From £3,200 (2 rooms) — £8,700 (5 rooms)
Fixed-price quote, held to the day.
2–4 days
Typical timeline from survey to commissioning.
5-Year Warranty
Parts and labour covered on every install.
F-Gas Certified
REFCOM-registered engineers on every job.
- Single outdoor footprint for whole home
- Independent temperature per room
- Cleaner external elevations
- Simultaneous cooling/heating on some models
Why choose this
- Single outdoor footprint for whole home
- Independent temperature per room
- Cleaner external elevations
- Simultaneous cooling/heating on some models
What's included
- Dual, triple, quad or penta configurations
- Mixed indoor types (wall, floor, cassette)
- Central WiFi hub for app control
- Shared electrical supply — saves on wiring
When multi-split beats single split
If planning restrictions, listed status or tight external space limit you to one outdoor condenser, multi-split is the only sensible answer. It also wins on aesthetics — one neat unit tucked to the side of the house is far less obtrusive than four scattered condensers.
Conservation-area homes, terraced houses with shared side alleys and flats with communal external walls are all classic multi-split candidates. Local authority planning officers routinely reject multi-condenser applications on aesthetic grounds; a single well-placed unit is far more likely to sail through.
Efficiency and running costs
Multi-splits typically achieve SEER 6.5–8.0, roughly 10–15% below matched single-splits. In practice this adds £15–£30 per year to running costs per zone — usually acceptable in exchange for the space and aesthetic gains.
Efficiency gap narrows when multiple zones actually run together. A five-zone multi-split serving a family home with everyone home in the evening runs at close to single-split efficiency because the load is diversified. Where the gap widens is in low-load scenarios — one bedroom cooling alone off a five-zone condenser is inherently less efficient than a dedicated single split.
Pipework strategy
Multi-split installs live or die on pipework planning. We favour hidden first-fix through stud walls or floor voids where the property allows; otherwise decorative white trunking (75 mm × 55 mm) run along the external wall is the neatest option.
On Victorian terraces we typically run pipes vertically down a corner, then horizontally into each room at high level — using a shared external riser and short internal runs. This looks tidier than snaking pipes across facades and keeps refrigerant charge low, which helps efficiency.
Configuration options
Multi-split condensers come in 2, 3, 4 and 5-port configurations, with total capacity from 5.2 kW (dual 2.6 kW) up to 14.5 kW (penta with mixed indoor sizes). You do not need to match all five ports on day one — a triple-port condenser can serve two rooms initially with a third indoor added later, provided we install a service valve stub at commissioning.
Indoor unit types can be mixed on the same outdoor. A single condenser can drive a wall unit in the master bedroom, a floor unit in the lounge and a ceiling cassette in the loft office — all with independent temperature set-points and scheduling.
Managing shared refrigerant
All indoor units share the same refrigerant loop, so an oil-return event or a service call temporarily affects every zone. To minimise disruption we specify condensers with dual isolation valves per port — a fault on one indoor can be isolated without pumping down the whole system.
Annual servicing is more involved than for single splits — coil clean and drain check at every indoor plus a full outdoor service and refrigerant charge check. Budget £180–£240 per year for a 3–5 zone multi-split service contract.
Real-world example: Victorian semi
A recent five-bedroom Victorian semi in Fulham needed AC in master bedroom, two children's bedrooms, home office and open-plan kitchen-diner. Conservation area permitted only one visible condenser. We specified a Daikin 5MXM90 (9 kW penta condenser) with three 2.5 kW wall units in bedrooms, a 3.5 kW in the office and a 5.0 kW floor unit in the kitchen.
Installed over four days including hidden first-fix through the loft. Total cost £8,240. First-year running cost across all five zones for combined summer cooling and shoulder-season heating: £312. Homeowner rating twelve months on: 'transformative.'
Balancing zones on a shared condenser
Multi-split condensers work by proportionally allocating compressor capacity to whichever indoor units are calling. The design challenge is ensuring no single zone can starve the others — a 5 kW lounge running flat out should not force the 2.5 kW bedroom into thermal drift because the compressor is capped.
We manage this at design stage by ensuring total connected capacity does not exceed 110–120% of outdoor rated. Modern electronic expansion valves per zone also keep refrigerant flow balanced dynamically. The result: every zone hits its setpoint even when others are demanding maximum capacity.
Pipework material and refrigerant charge
Multi-split installs typically require 30–80 m of copper piping in total across all zones. We use ACR-grade (Air Conditioning and Refrigeration) copper with sealed ends, brazed with silver-solder rather than lead-tin. Insulation is 13 mm closed-cell nitrile foam on liquid line, 19 mm on suction line — outperforming the 9 mm minimum most installers use and keeping condensation off pipe surfaces year-round.
Total refrigerant charge on a 5-zone 9 kW multi-split is around 3.6 kg of R-32 — well below F-Gas leak check thresholds (5 tCO₂e = 7.4 kg of R-32). Homeowners have no ongoing statutory obligation on typical residential multi-split systems.
Long-term serviceability and part supply
One outdoor condenser serving five indoor units means one point of failure. We stock same-day emergency loan units for Daikin and Mitsubishi 5-port condensers, so a serious fault means at most 48 hours of downtime while we swap the outdoor and arrange parts.
Parts supply for Daikin, Mitsubishi and Panasonic 5-port units is guaranteed by the manufacturer for 10 years from date of purchase. LG guarantees 7 years. Beyond guaranteed supply, third-party PCB and fan-motor equivalents are available and safe to use — extending the practical service life to 15–20 years for the outdoor and effectively unlimited for the indoor cassettes and wall units.
Design considerations for period and listed buildings
Grade II listed and conservation-area homes present specific multi-split challenges. External condensers usually require Listed Building Consent even when planning permission is not needed under Article 4 direction. We produce heritage impact assessments as standard for all listed applications — 20-page reports covering visual impact, physical intervention detail, reversibility and comparison against modern alternatives (electric heating vs heat pump vs AC).
Internal pipework routing through listed fabric needs equally careful thought. Chasing pipe into original lath-and-plaster walls is almost never permissible; we route through modern additions (loft conversions, rear extensions) or use decorative external trunking in heritage colours (RAL 7016 anthracite works well against most brick colours). Success rate on listed applications where we prepare the paperwork: 91% first-time approval, 100% second-time after amendments.
Multi-split for HMOs and small commercial
HMO landlords are increasingly specifying multi-split for shared houses — one outdoor unit visible on the rear elevation, one indoor unit per bedroom, tenant-controlled setpoints with landlord-set limits. This suits both the building envelope (one condenser vs five) and the operational model (tenants pay their own electricity through smart submeters).
Small serviced offices, dental practices and clinical rooms often follow the same pattern — 3–5 treatment or consultation rooms served by a single external condenser, each room individually controlled with weekend setback and infection-control-compliant filtration. The multi-split architecture keeps capex proportionate to a small-business fit-out budget while delivering commercial-grade individual zone control.
Frequently asked questions
Can I run heating in one room and cooling in another?＋
Only on 3-pipe simultaneous systems (typically VRF class). Standard multi-splits are heat-recovery-limited — all indoor units run the same mode.
What if I add a room later?＋
The condenser has to be sized upfront. If you might add a room within 5 years, we specify one size larger to leave headroom.
Is one big condenser noisier than one small one?＋
Marginally — a 9 kW condenser is around 51 dB vs 46 dB for a 3.5 kW single. Still quieter than an average conversation.
How much wall space does the outdoor unit need?＋
A 5-port condenser is typically 990 mm wide, 940 mm tall and 320 mm deep, with 300 mm clearance each side and 500 mm to the front.
Can indoor units be different brands?＋
No — all indoor units must be from the same brand and compatible product family as the outdoor. Mixing brands voids warranty.
What if the condenser fails?＋
All zones are offline until repair. This is the main downside of multi-split. We keep swap-in loan units for warranty customers to bridge repair windows.
How much pipework can a multi-split handle?＋
Typically 30 m per branch and 60 m total from outdoor to furthest indoor, with 20 m maximum vertical rise. Long pipe runs need refrigerant top-up (calculated by us).
Does it work if some zones are off?＋
Yes — inactive zones close their electronic expansion valve; the compressor modulates to serve only active zones at whatever partial capacity they demand.
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