Commissioning a split means the refrigerant circuit has been properly connected, evacuated and charged for the pipe length, the drain has been proved, the electrics are safe, and you have been shown how to run it. You should leave with model and serial numbers, the installing company's F-gas details, a short commissioning record, and warranty registration or a date when it will be done. Larger refrigerant charges have extra legal records. A domestic bedroom unit still deserves the same workmanship. Survey decisions should already be finished before this visit.
Flares, a held vacuum, and a charge for this pipe run
Hanging the indoor unit and standing the outdoor unit is the visible half. The important half is the flare or braze quality, nitrogen pressure test where the method requires it, a deep vacuum held long enough to show the circuit is dry and tight, and a charge that matches the pipe length rather than whatever was left in the outdoor unit from the factory.
Water through the tray, not a hopeful fall
Then the drain. Water should be run through the indoor tray so a fall or a pump is proved, not assumed. An untested pump is how a new ceiling gets a stain in the first hot week. Electrical isolation and a sensible supply are part of the same visit, with whatever certificate the electrical work requires.
The sheet that names this system
Indoor and outdoor model codes and serial numbers, the date, the pipe length, the company name and F-gas certification reference, and a note of what was checked.
- Vacuum and leak integrity, not a quick gas-and-go.
- Charge corrected for pipe length.
- Modes demonstrated: cool, heat if you have it, and a quiet fan.
Apps, filters and the record that applies to your charge
If an app was part of the sale, it should be connected while they are there. Filters and how to clean them should be shown, not left in a PDF you will not open. Warranty registration should be confirmed or dated. For systems with larger refrigerant charges, ask what F-gas records the law requires and who keeps them. GOV.UK is where company certification sits. Small domestic splits do not all produce the same commercial logbook. Ask what applies to yours instead of assuming either a huge dossier or nothing at all. The company certificate shows they may handle refrigerant. The pack shows what they did on your system. Ask for both. Daikin and Mitsubishi Electric installs are no exception to that pack.
A bucket, no gauge, and a coil hard against the wall
No vacuum gauge, a promise to come back and register it with no date, condensate into a bucket, and an outdoor unit tight against a wall so the coil cannot breathe. Those are reasons to stop the handover. You are allowed to ask for the readings. If the outdoor position has not been agreed, commissioning it in the wrong place locks in noise and planning trouble. The survey comes first. F-gas skill does not choose a legal wall by itself. Energy Saving Trust describes air-to-air heat pumps. It does not replace the readings.
Write to the company that invoiced you
Write to the company that invoiced you and list what you still need: serial numbers, F-gas details, commissioning notes, warranty registration. Do not invite an unrelated engineer to open the circuit. Another person adding refrigerant can muddy both the warranty and the legal responsibility. A factory charge does not make the flares, the vacuum or the electrics a weekend job. Opening the circuit is F-gas work. Photos of the data plates are worth taking while the installer is still on site. On the next job, commissioning paperwork is part of the price.
Frequently asked questions
Should I get a written commissioning sheet for a bedroom split?
Yes. It can be short. It should identify the equipment, the company, the checks on vacuum, charge and condensate, and the F-gas details. A verbal 'all done' is not a record.
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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.