The short answer
A straightforward single-room installation usually takes half a day to a full day. Longer or hidden pipe routes, extra rooms, electrical work and difficult access can each add time, sometimes a day or more.
On this page
Time on site depends far more on the route the pipes take than on the size of the unit. Two installations of the same model can differ by most of a day if one has pipes straight through the wall and the other runs them through a loft. The ranges below are typical, and an installer who has surveyed your home can give a firmer estimate.
Typical times
These are for the work itself, from arrival to handover, for wall-mounted systems.
| Job | Typical time on site | What drives it |
|---|---|---|
| One indoor unit, outdoor unit directly behind | Half a day to a day | The simplest layout |
| One indoor unit further away or upstairs | About a day | Pipes along or down the outside wall |
| One indoor unit, pipes hidden indoors | One to two days | Lofts, cupboards or floors |
| Two indoor units on one outdoor unit | One to two days | Length of each pipe route |
| Three or more indoor units | Two to three days or more | Pipework and testing for each room |
Systems with several indoor units take longer because every room has its own hole, pipe run and drain. How they work is explained in multi-split systems.
Why some steps can't be rushed
A few parts of the job take the time they take, however experienced the engineer.
- Core drilling. Usually quick through brick, slower through hard stone, concrete or very thick walls.
- Pressure testing. The pipework is held at pressure with nitrogen long enough to show a leak. Temperature changes move the reading, so a careful engineer lets it settle before judging it.
- Vacuum. Drawing air and moisture out of the pipes takes longer with long pipe runs and in cold, damp weather.
- Test running. The system needs to run in cooling and heating long enough to show it's working properly.
If a job is finished much faster than expected, it's reasonable to ask how long the pressure test and vacuum ran for. The full sequence is set out in what happens on installation day.
What can add time
- Long or complicated pipe routes, especially through lofts, floor voids or fitted cupboards
- An outdoor unit high on a wall that needs a tower or scaffolding, which may go up on a separate day
- A base to prepare for a ground stand, such as laying slabs
- A condensate pump, where water can't drain away by gravity
- Extra refrigerant for a pipe run longer than the factory charge covers
- Surprises in the wall, such as an unexpected pipe or cable that means moving a hole
- Material that might contain asbestos in an older home, which can mean stopping until it has been checked
- Heavy rain or strong wind, which can pause work outside or at height
The electrical work
Most systems need their own circuit from the consumer unit. The engineer may connect it on the same day if they're qualified to, or a separate electrician may do it, sometimes on another day.
A short, direct cable route from the consumer unit to the system is quick. One that crosses the house, or a consumer unit with no spare space or that needs other work first, takes longer. The detail is in electrical requirements.
Planning around the work
- Be home at the start to agree positions and at the end for the handover, which includes a walk through the controls.
- Expect your electricity to be off for a while when the new circuit is connected.
- Drilling is loud but usually brief. The longer testing stages are quiet, so working from home is usually possible.
- If a job spans two days, open pipe ends should be sealed overnight to keep out moisture and dirt, and the system can't be used until everything has been tested.
Getting rooms, access and parking ready before the engineers arrive keeps the day on schedule, as explained in preparing your home for installation.
Related guides
- What happens on installation dayInstallers fix the indoor and outdoor units, link them with insulated pipes through a hole in the wall, test the pipework for leaks and clear it of air, then connect the power, run the system and show you how to use it.
- Preparing your home for installationClear space around where the indoor and outdoor units will go, make sure the engineers can reach the consumer unit and anything on the pipe route, and plan for the power being off for a while.
- Multi-split systemsA multi-split system runs two or more indoor units, usually in different rooms, from one outdoor unit. Each room has its own controls, and your home needs only one outdoor unit rather than one for each room.
- Electrical requirementsMost wall-mounted systems need their own circuit from the consumer unit, often with an isolator switch near the outdoor unit. In England and Wales a new circuit is notifiable building work, so it's done by a registered electrician or notified to building control.