Quick answer
Most commercial HVAC equipment in the UK is serviced quarterly or six-monthly, with filter checks monthly to quarterly and fuller services annually. The right frequency depends on the equipment, how hard it works, manufacturer guidance and statutory checks such as F-gas leak testing. Many operators set frequencies using the SFG20 maintenance standard, adjusted after a site survey.
Why there is no single answer
A commercial building rarely has one HVAC system. It has a collection of assets, each with its own wear pattern: filters that clog, belts that stretch, drains that block, refrigerant joints that can leak and sensors that drift. Good maintenance schedules set a frequency for each task on each asset, rather than one visit frequency for “the air conditioning”.
Three things drive the frequency:
- Manufacturer guidance, which may also be a warranty condition.
- Duty and environment. A fan coil in a busy, dusty retail unit needs more attention than one in a quiet meeting room.
- Statutory checks, such as F-gas leak testing, which set minimum intervals for some equipment.
Typical frequencies by equipment
The table below shows common starting points. They are not a substitute for a site-specific schedule.
| Equipment or task | Typical frequency | Notes |
|---|---|---|
| AHU filters | Monthly to quarterly inspection | Change on pressure drop where gauges are fitted |
| AHU full service | Six-monthly to annual | Fans, belts, coils, dampers, drains, controls |
| Fan coil units | Annual service, filters more often | Condensate pumps may need more frequent checks |
| Split and VRF air conditioning | Six-monthly is common | Pre-summer visit is especially valuable |
| Chillers | Quarterly, with an annual major service | Trend operating data between visits |
| Heat pumps | Annual minimum | Check defrost and flow temperatures |
| Ventilation fans | Six-monthly to annual | Belt-driven fans need more attention than direct-drive |
| HVAC controls and sensors | Annual review | Sensors drift; check calibration and schedules |
Statutory checks that set minimum intervals
F-gas leak checks
Equipment containing fluorinated refrigerants at or above 5 tonnes of CO2 equivalent must be leak checked by certified engineers. Under the GB F-gas rules the typical intervals are:
| Refrigerant charge (tonnes CO2e) | Without leak detection | With leak detection |
|---|---|---|
| 5 to under 50 | Every 12 months | Every 24 months |
| 50 to under 500 | Every 6 months | Every 12 months |
| 500 and above | Every 3 months | Every 6 months (leak detection required) |
Records must be kept. Check the current GOV.UK guidance, as rules are periodically updated.
TM44 air conditioning inspections
Air conditioning systems with an effective rated output over 12 kW need an energy inspection by an accredited assessor at least every five years. It is separate from servicing, but good service records make it easier.
Legionella control
Where HVAC plant includes water systems that can create aerosols, such as humidifiers, evaporative coolers or cooling towers, the legionella risk assessment sets the monitoring and cleaning frequencies.
Using SFG20 sensibly
SFG20 is the industry standard maintenance specification for building services. It groups tasks by criticality, separating statutory tasks from those that protect the asset or improve efficiency. Use it as the starting point, then adjust using what you learn on site.
Signs your frequencies are wrong
- Too infrequent: recurring faults between visits, filters found heavily loaded, drains repeatedly blocked, energy use creeping up.
- Too frequent: components consistently found clean and in good order, with no deterioration across several visits.
Next steps
If you are unsure whether your schedule is right, an HVAC system assessment gives you an accurate asset list and a recommended schedule. To put it into practice, see HVAC maintenance contracts.
Frequently asked questions
Is annual servicing enough for commercial air conditioning?
For lightly used split units, an annual service plus periodic filter checks may be enough. Heavily used systems, VRF installations and anything serving critical spaces usually need at least two visits a year. F-gas leak-check intervals may require more.
Does SFG20 set legal maintenance frequencies?
No. SFG20 is an industry standard maintenance specification. It is widely used and often referenced by insurers and clients, but legal requirements come from regulations such as the F-gas rules and workplace health and safety law.
Should frequencies change for older equipment?
Often, yes. Older plant with a history of faults may justify more frequent inspection, while a condition-based approach can extend intervals for equipment that consistently shows no deterioration.
UK guidance and references
Primary and industry sources relevant to this subject. Always check the current edition and how it applies to your building.
- SFG20 standard maintenance specification BESA / SFG20
- F gas in refrigeration and air conditioning GOV.UK
- Air conditioning inspections for buildings GOV.UK
- Legionnaires' disease (ACOP L8) Health and Safety Executive
This guide is general information for commercial building operators. It does not replace an assessment of your building by a competent engineer. If there is an immediate risk to people, contact the emergency services first.