Do not accept a quote that only says a brand and a kilowatt. The decision is to insist on the indoor model code and the outdoor model code, because those codes are the machine you will live with. They fix cooling duty, sound, refrigerant and whether that indoor unit is allowed on that outdoor unit. A survey chooses the codes. An F-gas certified company installs that pair, not a substitute that happens to be on the van.
The indoor code and the outdoor code
Manufacturers sell several indoor units at a similar nominal kilowatt. They do not share the same sound on a low fan, the same size on the wall, or the same combination list. '2.5 kW Daikin' can mean more than one product. The code is how you stop a quiet bedroom model being swapped for a cheaper commercial head. The outdoor code sets the refrigerant, often R32 on current domestic splits, the pipe limits and which indoor units are a matched pair. Energy Saving Trust treats the reversible outdoor units as air-to-air heat pumps. The code tells you whether heating is part of that match.
Ask for both codes on the written quote before any deposit. Photos of the room and the outdoor elevation are there so the codes suit the wall and the noise, not a default package.
Laying two quotes side by side
Lay the codes side by side. If both quotes name the same pair, you are comparing install quality, drain, electrics and price. If they name different pairs, you are comparing different machines, and the cheaper quote may be a smaller coil or a louder outdoor unit. Ask for the cooling capacity and the sound figure that belong to those codes.
Data plates, refrigerant and a listed pair
A new indoor unit on an old outdoor unit is not a free choice of code. The old outdoor model has a combination list. If the new indoor code is not on it, the pair is not a repair, it is a mix that the manufacturer does not support. Different brands, and often different generations of the same brand, do not interchange. That is a survey question, answered from the data plates, not from the shape of the casing. Refrigerant type has to match. An F-gas certified company can recover and recommission a lawful pair. They should not be asked to invent a match that the datasheet refuses. If you already have equipment, photograph both data plates and ask the firm to confirm the new code is a listed combination, or to price a full new pair instead of a mix.
Frequently asked questions
Is the kilowatt enough if the brand is one I know?
No. The same brand sells several indoor units at one nominal duty. The code is what fixes noise, size and the outdoor unit it may connect to.
Can the installer fit a different code if mine is out of stock?
Only with your agreement, against a code you have checked. A swap after the quote is a different product and can void the comparison you thought you had made.
Where do I find the code on a unit I already own?
On the data plate of the indoor unit and the outdoor unit. Photograph both. The marketing name on the front is not the combination code.
What should I do with a line that says or equivalent?
Strike it, or define the equivalent as the same capacity, the same refrigerant and a sound figure no worse, written down before the deposit. That line is a licence to change the machine after you have agreed the price.
Will a current bedroom range marry an outdoor unit from ten years ago?
Often it will not, even inside one brand. If your outdoor model is missing from the combination list, no installer should be asked to make it work with a different flare or a guess at the charge.
Core buying guides
Start with these high-intent guides, then dig into the rest of the library.
Related guides
Sources and further reading
How this guide was prepared
This guide was written by the Local AC Installers Editorial Team. We compare official guidance, legislation and established consumer information, separate general information from project-specific advice, and show publication dates and sources. We do not accept installer accreditation claims at face value.