Commercial air conditioning doesn’t usually go from working perfectly to complete failure without showing some warning signs first. Changes in airflow, new noises, recurring fault codes or water where it shouldn’t be can all give you an opportunity to investigate before the problem becomes more disruptive.
A good commercial air conditioning maintenance checklist isn’t about turning a facilities manager into an AC engineer. We’d use it to spot changes between professional service visits, keep better maintenance records and give the engineer useful information when something needs investigating.
There’s also a clear line between observation and maintenance. Checking whether airflow has dropped is sensible. Opening electrical panels or connecting gauges to a refrigerant circuit isn’t. GOV.UK confirms that servicing, maintaining and leak checking equipment containing F-gas requires the appropriate qualifications. See GOV.UK’s current F-gas qualification requirements
For most commercial premises, we’d suggest building the following observations into your normal facilities inspections. The frequency should reflect how critical the system is, how heavily it runs and the environment it operates in.
Don’t just ask whether the room feels hot. Record what’s actually happening.
If a room normally maintains 21°C but is sitting at 25°C despite the controller still being set to 21°C, note the actual temperature, controller setting, operating mode and time of day. Check whether nearby rooms served by the same system are experiencing the same problem.
That information immediately gives an engineer somewhere to start. Poor cooling can be associated with restricted airflow, dirty heat exchangers, control problems or faults within the refrigeration circuit. Trane’s troubleshooting guidance shows how airflow, filter condition and refrigeration faults can all contribute to poor cooling performance.
Also consider whether anything in the room has changed. Extra IT equipment, a higher occupancy level or a change in how the space is used can increase the cooling load without there being anything mechanically wrong with the AC.
Stand beneath the supply grille or cassette and compare the airflow with what you normally experience. You’re looking for a noticeable change rather than trying to take an engineering airflow measurement yourself.
Reduced airflow can be associated with filter loading, a dirty evaporator coil or a fan-related issue. Manufacturer guidance also identifies clogged filters as something that can affect system operation and performance. Carrier’s maintenance guidance explains why filter condition affects airflow and coil performance.
Before raising a fault, check the simple external factors too. We’ve attended commercial sites where furniture, storage or changes to a room layout have restricted an otherwise healthy supply or return air path.
If several outlets suddenly have weaker airflow, or airflow continues to deteriorate after obvious obstructions have been ruled out, we’d arrange an engineer inspection rather than assuming the filter is the only cause.
Where filters are designed for safe user access, inspect their condition in line with the manufacturer’s instructions.
We wouldn’t assume every filter needs changing at exactly the same interval. A unit serving a relatively clean office may load very differently from one operating near a busy road, kitchen or heavily occupied commercial area. Carrier specifically recommends using regular visual inspection to establish an appropriate replacement frequency because operating conditions vary between premises. See Carrier’s guidance on assessing air filter condition.
If filters are becoming dirty much faster than they used to, record that change as well. It gives us something useful to investigate during the next service rather than simply replacing the filter and forgetting about it.
Water around an indoor unit deserves attention even if it’s only a small amount.
An air conditioner naturally produces condensate during cooling, but that water should reach the drainage system rather than the ceiling, wall or floor. A leak can relate to drainage problems, a condensate pump issue or problems affecting how water leaves the evaporator coil. Trane’s commercial technical guidance shows that airflow conditions, drain arrangements and other internal issues can all contribute to condensate problems. See Trane’s guidance on investigating condensate leaks.
When reporting the problem, tell us:
A mistake we often want to avoid is treating every water leak as simply a blocked drain. Clearing visible water doesn’t explain why it appeared. If the underlying cause is a failed pump or another drainage fault, the leak can return and damage ceilings or finishes.
Different noises point engineers towards different areas of the system.
If something changes, record whether you’re hearing vibration, rattling, mechanical contact or another clearly abnormal sound. Note whether it happens at start-up, continuously or only when the unit changes operating mode.
Not every unfamiliar noise means a fault. Daikin, for example, explains that a water-flowing sound can simply be refrigerant moving through the system during certain operating conditions. Manufacturer maintenance guidance does, however, identify abnormal mechanical sounds and obvious resonance as items worth investigating. See Carrier’s guidance on checking abnormal AC noise.
A short video recorded safely from the occupied space can be extremely useful if the noise disappears before an engineer arrives.
If a controller or BMS displays an error, record the complete code together with the asset and time.
Don’t repeatedly reset a system simply to make the warning disappear. The fault code may be one of the most useful pieces of information available when we begin diagnosis.
Manufacturers use specific codes to identify very different faults. Daikin’s technical support service, for example, asks engineers to have the full model number available when diagnosing problems and provides dedicated support for fault-code interpretation. See Daikin UK’s technical fault support guidance.
For a facilities management AC checklist, we’d record the code exactly as shown rather than trying to interpret it yourself.
Where you can see outdoor units without entering a restricted area or working at height, look for obvious physical changes.
Check for debris restricting the coil, damaged panels, deteriorated pipe insulation or something newly stored against the unit. Restricted condenser airflow can affect how effectively the system rejects heat.
Don’t turn a routine facilities inspection into roof work. HSE guidance says maintenance should be properly planned, staff must be competent and safe access needs to be provided where unusual or elevated areas are involved. Read HSE’s guidance on planning maintenance safely
If your condensers are on a roof, behind guarded plant or in another controlled area, leave the physical inspection to the maintenance visit.
The facilities team’s job is primarily to identify symptoms and keep useful records. During planned preventive maintenance, we’d go considerably further.
Depending on the equipment and service scope, professional checks can include:
These are the types of checks included within Houlkair’s own air conditioning maintenance service. Where refrigerant work or F-gas leak testing is involved, the technician must also hold the relevant qualification. GOV.UK explains the certification required for companies working on stationary air conditioning systems.
Trying to extend an in-house AC preventive maintenance checklist into electrical testing or refrigerant diagnosis can create unnecessary safety and compliance problems.
One area we think facilities teams can improve significantly is the quality of the information attached to each asset.
A note saying “AC not cooling, please investigate” has limited diagnostic value. A better entry might say:
Meeting Room 2, AC-014. Controller set to 21°C in cooling mode. Room remained at 25°C at 14:30. Airflow noticeably weaker than AC-015 next door. No fault code showing.
That gives us something we can test against immediately.
Your asset register should ideally connect the indoor unit with the equipment it depends on, including the relevant outdoor unit, controller and served area. Larger commercial installations can become surprisingly interconnected. On our St James commercial replacement project in Manchester, for example, the works involved a BC controller alongside 105 metres of roof-level pipework. A register containing only the room name wouldn’t describe enough of the system to make future fault finding straightforward.
For each maintenance record, we’d include:
This turns maintenance documentation into a history rather than a collection of service sheets. The Government’s Facilities Management Standard also expects organisations to maintain an FM asset register, with the level of detail reflecting the criticality of the building and its equipment. See the Government Facilities Management Standard on asset registers and forward maintenance planning
Your air conditioning servicing checklist should sit alongside the building’s compliance records rather than replace them.
For equipment containing at least 5 tonnes CO2 equivalent of F-gas, GOV.UK requires records covering items such as the gas contained within the equipment, maintenance additions and mandatory leak-check results. Those records need to be retained for five years. See GOV.UK’s F-gas record-keeping requirements.
Leak-check intervals are also based on the amount of F-gas expressed as CO2 equivalent. Equipment containing 5 to less than 50 tonnes CO2 equivalent generally requires checks at least every 12 months, with shorter intervals applying at higher thresholds unless qualifying leak detection changes the permitted interval. Check the current GOV.UK F-gas leak-check requirements.
Separately, air conditioning systems in England and Wales with a combined effective rated output above 12kW fall within the statutory air conditioning inspection requirements. These inspections must take place at intervals no longer than five years and aren’t the same thing as routine servicing. Read the current GOV.UK guidance on air conditioning inspections.
Keeping those requirements in the same maintenance schedule reduces the chance of a service visit being mistaken for a statutory inspection, or vice versa.
We’d bring an investigation forward if you find an active water leak, repeated fault code, major reduction in airflow or a significant change in cooling performance. New mechanical noise and repeated system shutdowns also justify further investigation rather than waiting months for the next planned visit.
Where a unit serves a critical room, the threshold should be lower. Cooling problems affecting server rooms, healthcare areas or another temperature-sensitive space can become an operational issue much faster than a comfort complaint in an ordinary meeting room. Houlkair’s breakdown service specifically covers cooling failures, leaks, airflow problems and unusual noises because these symptoms often need diagnosis rather than simple observation. See Houlkair’s commercial AC repair and breakdown service.
The most useful commercial air conditioning maintenance checklist isn’t the one with the greatest number of checks. It’s the one that lets you recognise when an asset is behaving differently from normal and gives the engineer enough information to understand what changed.
Keep an eye on temperature performance, airflow and visible condition. Record water leaks, unusual noises and fault codes properly. Then use engineer reports, service history and remedial actions to build a picture of each asset over time.
That’s how we’d use a commercial AC maintenance checklist within a wider PPM programme: facilities teams provide early warning and good records, while qualified engineers carry out the technical maintenance and diagnosis needed to keep the equipment reliable.