Aircon Commissioning Readings: The Record Nobody Asks For

Commissioning is the point where a new system is proven to work correctly, not the point where it is switched on. Switching on shows that power reaches the unit and the fan turns. Commissioning shows that the sealed circuit was prepared properly, filled with the right weight of refrigerant, and running as the maker intended.

A brand new aircon blows cold on handover day almost regardless of how carefully it was put in. A shallow vacuum, a charge estimated instead of weighed, a service valve left part open: none of those stop cold air at the grille that first afternoon. What they do is shorten the life of the machine and raise running cost.

That gap is why commissioning has to be written down rather than felt. A walkthrough at sign-off is a good observation exercise, confirming each unit responds, drains and cools. It cannot confirm anything about the sealed circuit, because a sealed circuit shows no symptoms on the day it is filled.

Neither side is hiding anything here; the figures simply never come up. Owners do not know to ask, installers are not routinely asked, and a record nobody requests is a record nobody keeps. The result is a stock of Singapore flats whose original condition was never captured.

Five figures carry almost all of the later value. Each pins down a different part of the system at the one moment when everything was new, the installer was still in the flat, and the instruments were already out. Recorded together they describe a specific machine in a specific home.

The vacuum reached before charging is the only one that can never be recovered afterwards. After the gas goes in, the state the pipework was left in becomes unknowable. A written figure, with a note on whether it held after isolation, is the entire evidence trail for that step.

The weighed charge is the figure most often missing and most often needed. A split system ships with a factory charge sized for a nominal pipe length, and any run beyond that needs refrigerant added by weight. A proper record shows the factory figure, the addition for the actual run, and the total that went in.

Running pressures and the air temperature drop describe how the system behaved once it settled. Pressures from both sides go on the sheet with the outdoor conditions beside them, and that pair becomes the reference a future set of pressures is read against. The air temperature drop is the only line an owner can repeat alone.

Compressor running current closes the electrical side. A compressor draws a characteristic current for a given load, and that figure drifts as windings age, bearings wear, or the system is pushed harder than intended. Captured at commissioning, it becomes the line every later reading is measured against.

Every diagnosis is a comparison. A technician looks at what a system is doing and decides whether that counts as normal. Where a commissioning record exists, normal is a documented fact about this machine in this flat; where it does not, normal is an estimate from other machines.

That estimate is looser than most owners assume. Two units of the same model and capacity will not read the same once fitted. Pipe run length, how the outdoor unit sits, how much afternoon sun the ledge takes and what the room is doing all move the figures.

So a technician meeting a system new to them has to rebuild the baseline before any diagnosis. That rebuild is judgement, and judgement is where honest technicians differ. A commissioning record removes the rebuilding step, swapping an opinion about what normal should be for a measurement of what normal was.

This is the difference between a complaint and a case. A room that does not feel as cold as it used to cannot be tested, and it earns an opinion in reply. A temperature drop several degrees narrower than the commissioning figure, on the same fan setting, can be tested.

The warranty period is where an absent record costs real money. A fault under cover raises one question ahead of every other: was the part defective, or was the system fitted and filled wrongly? Makers stand behind the first; installers stand behind the second. Nobody stands behind an argument that cannot be settled.

Without figures from the day, that question has no factual answer. A compressor that dies young might have failed on its own, or spent its whole life running against a wet circuit or a charge that was never right. Both stories fit the same dead compressor equally well.

With the figures, the question turns into arithmetic: three entries settle it between them. The vacuum was reached and it held. The weighed charge matches the nameplate plus the allowance for the pipe run. The settled pressures sit inside the window the maker states, which establishes that the system left commissioning in the state it was meant to be in.

Ask for the record in a form that survives. A photo of the gauge, a filled commissioning sheet, or a written summary in the installer's own message all work equally well. Verbal confirmation on handover day converts into nothing at the moment it is needed. Store it where the warranty card lives.

Raise the readings while quotes are still being compared. An installer who knows the figures are expected turns up with the instruments and takes them as part of the job. An installer told at sign-off has nothing to write on, because the moment for capturing most of those figures has gone.

Asking early also changes the quotes in a useful way. Proper commissioning takes instruments, attention and a technician willing to stand behind what the gauge said. A quote priced with that in it reads differently from one priced without, and the difference is the information.

Put the request in writing at the point of acceptance, and keep it to what the installer should already be reading:

• •The final vacuum figure at the system, and how the gauge behaved once the pump was shut off
• •Nameplate charge, the extra weighed in for the pipe run, and the total in the circuit
• •Suction and discharge pressures once running had settled, with the outdoor conditions noted
• •Intake and outlet air temperatures at every indoor unit, with fan speed and set point beside them
• •Compressor running current, taken alongside the pressures rather than separately
• •Model and serial numbers of each indoor and outdoor unit, so the figures tie to the actual machines

Most systems in Singapore flats were handed over with nothing written down at all, and there is no way to go back for it. The vacuum figure is gone for good. The weighed charge is gone unless the installer kept a job sheet, which is worth one polite request.

The workable move is a baseline captured now, while the system is behaving. A baseline taken from a healthy machine does nearly the same job as one taken from a new machine, since the purpose is identical: to be the thing a future reading gets compared against.

Part of it needs no technician. The air temperature drop across each indoor unit, taken at a fixed fan speed with room conditions written beside it, needs one thermometer and no access to the sealed circuit. Repeat it now and then and the record builds itself. Everything on the refrigerant side needs gauges, which makes the next service visit the natural moment to ask.

Ask for those figures to be written down at a visit where nothing is wrong. A service report that captures a healthy system is among the most useful documents a homeowner can hold, and it is almost never requested. A visit where a fault is already present is the wrong occasion.