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Split, multi-split or VRF: which commercial air conditioning?

Updated 23 October 2026 · SEO Dons Editorial

What is the difference between a split, a multi-split and VRF?

The government's Energy Technology List (ETL) defines all three by how many indoor units hang off an outdoor unit and how they are controlled. The definitions turn on the refrigerant circuit and the controls, not on size.

SystemIndoor units per outdoor unitRefrigerant circuit and control
Single splitOneOne outdoor unit and one indoor unit
Multi-splitTwo or moreIndividual circuits with units individually controlled, or a common circuit with units controlled as one
VRFOne or moreA common circuit with indoor units individually controlled

Two things follow. Separate single splits are separate systems, so each room can run in its own mode. A common-circuit system shares its outdoor unit, and whether it can heat one room while cooling another depends on the model. The VRF answer is in heat recovery or heat pump VRF.

How many zones before splits stop making sense?

Makers publish a limit for each range. LG's UK page says "In the case of the Multi Piping Type, a single outdoor unit can support up to five indoor units", and the figure differs by maker and model.

A rule of thumb, not a standard. Up to about five separately controlled rooms, compare single splits and multi-splits. Beyond five, or where zones sit on several floors, ask for VRF to be priced alongside. The basis is one maker's published limit and simple arithmetic: past that count a multi-split design needs a second outdoor unit, with its own pipework, power and controls. Check the data sheet for the actual model.

Count the indoor units on the inspection side too. The TM44 guidance says inspection applies to "systems consisting of individual units which are less than 12kW, but whose combined effective rated output is more than 12kW", so six small splits can add up to an inspection every five years in England and Wales (see TM44 inspections). The installed cost ladder for each type, with a worked comparison, is in the commercial air conditioning cost guide, so no prices are repeated here.

How do refrigerant charge and leak checks compare?

GOV.UK says how often you must check for leaks "depends on the" amount of F gas in the equipment and its global warming potential. To get the CO2 equivalent, "multiply the mass of the gas (in metric tonnes) by the gas’s global warming potential (GWP)". GOV.UK lists R-410A at 2088 and HFC-32 at 675, and CIBSE gives R-32's GWP as 675 on the same basis. Checks are at least every 12 months from 5 tonnes, and at least every 6 months from 50 tonnes.

RefrigerantGWPCharge at 5 tonnes CO2eCharge at 50 tonnes CO2e
R-410A20882.4 kg (GOV.UK table)24 kg (GOV.UK table)
R-32675about 7.4 kg (calculated)about 74 kg (calculated)

Hypothetical charges, to show the effect. A multi-split holding 9 kg of R-410A holds 18.8 tonnes CO2e, so annual checks. A VRF system holding 30 kg of R-410A holds 62.6 tonnes, so six-monthly checks. The same 30 kg of R-32 is about 20.3 tonnes, back in the annual band. But CIBSE says R-32 "is classified as mildly flammable (A2L), which means safety provisions such as leak detection, ventilation and system charge limits must be considered in design". BSI says BS EN 378-1 "helps identify installation location and determine maximum charge suitable for the room volume". One circuit serving many rooms makes the smallest room the test.

The rules attach to the equipment. Article 4 applies to "Operators of equipment that contains fluorinated greenhouse gases in quantities of 5 tonnes of CO2 equivalent or more", and Article 6 requires "records for each piece of such equipment". For several separate splits, ask the F-gas contractor what each piece of equipment holds. New single splits under 3 kg are limited to refrigerants with a GWP of 750 or below from 2025, while "larger split systems" are listed among the exceptions (see is air conditioning being banned).

How do controls, maintenance and failure risk differ?

Controls. Individually controlled units suit multi-tenant floors and rooms with different hours. Units "controlled as one" do not.

Maintenance. Each indoor unit is a separate item to reach and service, so a higher count means more units to maintain. CIBSE adds that on VRF, "System complexity and the reliance on refrigerant distribution throughout the building can make diagnosis and repair more specialised". Servicing stationary air conditioning for others needs a certified company: GOV.UK says "Your company, including sole traders, must be certified by an approved body to service stationary equipment containing F gas operated by others" (see checking F-gas certificates).

Failure risk. Ask what happens to the other rooms if the shared outdoor unit stops. Separate splits fail one room at a time.

Efficiency. No family is automatically more efficient. Compare seasonal figures on one basis, as in reading SEER and SCOP.

Which suits which building? Worked examples

These are hypothetical illustrations.

  • A shop with a sales floor and a stockroom. Two single splits. Each room has its own mode, and a fault affects one room.
  • A practice with five consulting rooms. At the edge of the multi-split range. Price a multi-split against five single splits and compare outdoor space, charge and failure risk.
  • A 1,500 square metre multi-let office floor with twelve zones and a comms room. Beyond multi-split range, so VRF for the comfort zones, with the comms room cooled separately (see the indoor unit comparison for room types).

Whichever is proposed, the quote should state the indoor unit schedule, refrigerant, charge in kg and tonnes CO2e, leak-check interval and the manufacturer's pipe-length limits for the model. Readers can send an enquiry through the site's form, and the cost guide shows how to read the price ladder.

Sources

Common questions

Can wall units and cassettes share one multi-split?

Often, but it is set by the model. LG's UK page says one outdoor unit can accommodate "a diverse selection of indoor units", yet the permitted mix, combined capacity and pipe lengths come from each model's data. Ask for the proposed combination to be confirmed against that data.

Do several small splits avoid an air conditioning inspection?

No. The TM44 guidance counts a number of small units together when their combined cooling capacity is more than 12kW. It applies in England and Wales, and Scotland and Northern Ireland have separate rules.

Does switching to R-32 always reduce leak-check duties?

Not automatically. Its lower GWP means more kilograms are needed to reach each band, which can move a system down a band. R-32 is mildly flammable, so charge limits and safety measures must be considered in design.

Who is allowed to leak-check a commercial split or VRF system?

A company servicing stationary air conditioning for others must be certified by an approved body, and individuals handling F gas need personal qualifications. A business servicing only its own equipment does not need a company certificate.

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