Multi-head split system installation: up to five rooms on one outdoor unit

A multi-head split, also called a multi-split, is one outdoor unit feeding two, three, four or five indoor heads. Each head has its own remote and its own set temperature. The outdoor unit carries one compressor sized for the combined load, and separate refrigerant pipe runs go from it to every room. From inside each room it feels exactly like a single split; the difference is all outside.

The same-manufacturer rule. Every head on a multi-split has to come from the same manufacturer as the outdoor unit, and from the range that outdoor unit is designed to run. You cannot hang a spare head from another brand off it, and you cannot bolt a new head onto an old outdoor unit from a different family. That is how the systems are built, and it is also a condition of the Victorian discount when a multi-split replaces a gas heater.

Capacity is shared. The outdoor unit is usually rated a little below the sum of all its heads, because in a real house not every room runs flat out at once. That is fine for bedrooms and a study. It is a poor fit for a home where every room needs full output on the same afternoon, which is one of the things the office asks about.

One mode at a time. On most residential multi-splits, all the heads heat together or cool together. One room cannot be heating while the next is cooling. In Melbourne that almost never matters, but you should know it before you buy.

A multi-head wins when outdoor space is the problem. One outdoor unit on a bracket or a slab, one set of penetrations through the wall, and no roof space needed. That describes a lot of Melbourne housing: double-storey townhouses, Edwardian and interwar homes with tight ceiling cavities, and any home where the owners corporation limits how many outdoor units go on the wall. It also suits two to four rooms that are used at different times, because each head turns off on its own.

Separate singles win when the rooms are far apart, when you want to stage the spend one room at a time, or when you want no single point of failure. If the outdoor unit on a multi-split stops, every room stops with it. Four singles are four independent systems. They also let you mix brands and sizes freely.

Ducted wins when you want the whole house at one temperature with nothing on the walls, and you have the roof space to run the ducts. For a large single-storey home with a good ceiling cavity it is usually the cleaner result. Our ducted reverse cycle page covers that path.

The single vs multi-head guide and the ducted vs split comparison go into the trade-offs. The office asks about the rooms, the roof and the outside walls, and recommends one of the three without a sales pitch.

A multi-head split is one of the recognised ways to replace a ducted gas heater under the Victorian Energy Upgrades program. The old ducted heater is decommissioned, the gas line is capped by a licensed gasfitter, and a multi-split with same-brand heads takes over the heating and cooling of the main rooms. Our replace gas ducted heating page compares this path with a full ducted reverse cycle changeover and with separate singles.

How the discount works. FreshDuct arranges your VEU discount through our accredited installation partners. It comes off your quote up front, not as a cashback afterwards. The gas heater has to still be connected and be the main heating in the home, the new system has to be an approved high-efficiency model with same-brand heads, and a minimum co-payment applies, so it is never free. Our VEU heating and cooling discount page has the current details and the eligibility list.

Why people choose the multi-split path. A four-head system heats the rooms people actually use, gives each of them its own control, and removes the gas bill for heating entirely. It is usually a smaller job than a full ducted changeover and avoids the question of whether thirty-year-old ductwork should be reused. The trade-off is that hallways and the laundry stay unconditioned. For many Melbourne families that is exactly what they wanted.

A multi-head install is a bigger day than a single. The outdoor unit is larger and heavier, so it usually sits on a level slab rather than a light bracket, with clear airflow on all sides and as far from bedroom windows as the pipe runs allow. From it, a separate insulated pipe pair, drain and cable run to each head. On a single-storey brick veneer home those runs go along the eave in a duct cover and drop into each room. On a two-storey home the upstairs heads are usually the easier ones, with runs through the wall cavity and the outdoor unit at ground level.

Drains matter more on a multi. Four heads means four condensate drains, and a drain that ends in the wrong place shows up as a damp patch on a bedroom wall. We take every drain to an outlet by gravity where we can and fit a small pump where we cannot.

Electrical. One dedicated circuit from the switchboard feeds the outdoor unit, and the heads are powered from it, so the wiring is simpler than four singles. A licensed electrician runs it and fits the isolator.

Commissioning is done head by head: pipe runs vacuumed and pressure-tested, refrigerant charge adjusted for the total run length, every head run in heating and cooling, every remote set up. Expect a full day for three or four heads, sometimes two. The office confirms the time and the price before any work, and you pay after the job.