Air conditioning installation is a two trade job pretending to be one. There is a refrigeration side, which is pipework, vacuum and charge, and there is a building side, which is holes, brackets, drains and a new electrical circuit. Most of what goes wrong afterwards was decided on the building side, before anybody switched anything on, and most of it is visible on the survey if the survey happens.
Home air conditioning installation: the survey decides almost everything
A surveyor is looking for three things: where the indoor head can go so the air actually reaches the room, where the outdoor unit can stand so it is not against a boundary or under a bedroom window, and what route the pipes and the condensate drain can take between them. A short, straight, hidden route is a cheap installation. A long one through a joisted floor and around a stairwell is not, and no unit choice changes that.
Installing air conditioner heads: what the day itself looks like
A single room system is usually a day. The team cores the wall, mounts the bracket and the indoor head, runs insulated refrigerant pipe, a drain and an interconnecting cable, stands or brackets the outdoor unit, connects the electrical supply, then pulls a vacuum on the pipework and holds it to prove there are no leaks before any refrigerant is released. A multi room job is the same work repeated with a longer first fix, so it runs into a second or third day.
Where aircon home installation goes wrong
The two common regrets are position and noise. A head mounted above a door blows at a wall, and a head over a bed blows at a person, and neither is fixable later without making good the pipework. Outdoor units are the other one: they are quiet from inside and audible from a neighbour's garden, and the fix after the fact is a relocation rather than an adjustment.
What you should end up holding
A commissioning sheet showing the pressure test and the charge, the electrical certificate for the circuit, the warranty registration in your name rather than the installer's, and a written service interval. Air conditioning installations that arrive without paperwork also arrive without a warranty when it is needed, because manufacturers ask for the commissioning record first.
Questions people ask about air conditioning installation
How long does installing aircon take?
One room is normally a single day for a competent two person team. Each further indoor head adds pipework and first fix rather than another full day, so a three room system is commonly two to three days. Old solid walls, long pipe routes and awkward outdoor positions add time before they add cost.
How much mess does it make?
Less than people expect indoors and more than expected outside. The wall core is a single clean hole made with a wet or vacuum assisted drill. The disruption is the route: lifting a floor, chasing a wall or boxing a run through a cupboard is what turns a tidy day into a job with making good afterwards.
Can I install air conditioning units myself?
You can mount hardware, but you cannot legally charge the system with refrigerant without the relevant personal certification, and the electrical circuit is notifiable work in a dwelling. Pre charged split kits exist and still leave you with an uncommissioned system, no manufacturer warranty and no certificate.
Does UK air conditioning installation need building regulations approval?
The new electrical circuit is notifiable, and where the work affects the fabric or fixed building services there are energy efficiency requirements that apply. The practical answer is that the certificates come from the installer, and you should establish which ones you are getting before the work starts.