Air-conditioning maintenance: why is it important, and how often should it be carried out?
Key points
1. There are two levels of maintenance: cleaning the filter every 2 to 4 weeks during the season, which you can do yourself in ten minutes, and an annual professional inspection, which covers the heat exchanger, the coolant and the electrical connections.
2. Contrary to popular belief, the periodic leak test required under the European F-Gas Regulation does not apply to the majority of domestic split-system air conditioners: the legal threshold is 5 tonnes of CO₂ equivalent, or approximately 7.4 kg of R32, which is well above the refrigerant charge of a standard single-split unit. Maintenance is, however, strongly recommended, as it helps to ensure the system’s warranty and performance.
A neglected system often lasts less than 10 years, compared with 15 to 20 years for a well-maintained system. The difference in cost over the system’s lifetime far exceeds that of regular maintenance.
What actually happens when you don’t maintain anything?
An air conditioner works on a simple principle: air passes through a heat exchanger, which cools or heats it depending on the season. As soon as the filter becomes clogged or the heat exchanger accumulates dust, the air does not circulate as well. The unit compensates by working harder and for longer to reach the same temperature, which consumes more electricity whilst delivering a poorer result.
This deterioration is not immediately apparent. It reduces efficiency by 5 per cent in the first year, then accelerates if nothing is done, until a 20 per cent loss is reached within two or three seasons. At this stage, the compressor – which is the most expensive part of the appliance – is subjected to repeated mechanical stress that shortens its lifespan. A well-maintained system lasts 15 to 20 years. A neglected system rarely lasts more than 10 years.
What do you do yourself, and how often?
The filter in the indoor unit should be cleaned every two to four weeks during the heating season. Remove it, rinse it under clean running water, and leave it to dry completely before putting it back in place. It only takes ten minutes, and it’s the step that makes the biggest difference: a dirty filter alone can increase energy consumption by 10 to 20 per cent.
It is important to check the condensate drainage system regularly, particularly during periods of heavy use. A blocked drain pipe will cause the collection tray to overflow and may damage a wall or ceiling before the problem is spotted.
Clearing the area around the outdoor unit completes this routine. Leaves, tall grass or objects piled up against the ventilation grilles reduce heat exchange, meaning the unit has to work harder to compensate. A quick check once a month during the season is enough to prevent this problem.
What does a professional do once a year?
The annual service covers aspects that you cannot check yourself, as they require access to the outdoor unit, measuring equipment and specific certification.
The technician thoroughly cleans the indoor and outdoor heat exchangers, which cannot be reached by hand. He checks the refrigerant charge and detects any slow leaks, which are not noticeable in day-to-day use but gradually reduce performance. He checks the electrical connections and measures the operating pressures; if these two points are neglected, they can lead to a compressor failure, which is the most expensive repair on this type of appliance.
In Belgium, an annual maintenance contract costs between €100 and €200 for a residential single-split system; this figure increases for a multi-split system depending on the number of indoor units connected. Compared with the cost of replacing a compressor (often €400 to €800) or a whole unit before its time, annual maintenance remains the cheapest option over the system’s lifetime..
Frequency | Current practice | Who does it? |
| Every 2 to 4 weeks during the season | Cleaning the internal filter | You yourself |
| Once a month during the season | Clearing the area around the outdoor unit, checking the condensate drains | You yourself |
| Once a year | Cleaning of heat exchangers, checking the fluid level, electrical checks | F-gas certified technician |
| Before winterisation (non-reversible systems) | Thorough cleaning and protection of the outdoor unit | You yourself or a technician |
What is actually compulsory, and what is not:
For R32, the standard refrigerant used in recent domestic air-conditioning systems, the GWP is 675. A charge of around 7.4 kg would therefore be required to reach the 5-tonne CO₂-equivalent threshold. However, a standard domestic single-split system typically contains between 1 and 3 kg of refrigerant. In practical terms, the vast majority of split-system air conditioners installed in Belgian homes fall well below this threshold and are therefore not subject to any legal obligation to undergo periodic leak checks.
What the regulations do, however, require – with virtually no exceptions – is that any handling of refrigerant must be carried out by an F-gas-certified professional. Recharging, repairing or recovering refrigerant yourself is illegal, regardless of the quantity. Annual servicing is therefore still recommended to ensure the appliance’s performance, to maintain the manufacturer’s warranty and to extend its lifespan, although it is not a strict legal requirement for most domestic installations.
This threshold of 5 tonnes of CO₂ equivalent applies in exactly the same way in Belgium, as the F-Gas Regulation is a European regulation that is directly applicable in all three Regions, without the need for national transposition. An installer who claims that an annual leak test is ‘legally mandatory’ for a standard residential single-split system is either mistaken or is selling you a service whose value lies solely in the benefits it provides, not in any legal requirement. |
Frequency by system type
Not all systems require maintenance at the same frequency, nor are they all equally easy to access.
The single-split system remains the simplest: an accessible filter and an outdoor unit that is generally unobstructed. The multi-split system involves monitoring multiple filters – one per indoor unit – which lengthens the routine without making it any more complicated. Ducted air conditioning, with its units concealed in a false ceiling, requires technical access for professional maintenance; this must be planned for at the project design stage by incorporating an access hatch. Finally, portable air conditioners are easy to maintain (with visible filters and condensate trays) but wear out more quickly with use, which does not mean they can be neglected – regular checks are still essential.
System | Filter access | Career interview |
| Monosplit | Easy | Simple, one unit |
| Multi-split | Easy, with several filters | Slightly longer, with several indoor units |
| Gainable | Requires an access hatch | Technical access must be provided at the time of installation |
| Mobile | Very easy | Rarely specified in contracts, wears out more quickly |
Signs you shouldn’t ignore
An unusual noise coming from the outdoor unit, a musty smell when the system starts up, and a longer time taken to reach the set temperature from one season to the next: these are the three most reliable signs that maintenance is overdue. The musty smell, in particular, is often caused by a build-up of moisture on the indoor heat exchanger, which provides a breeding ground for bacteria. Some manufacturers, such as Samsung with its Auto Clean function, include an automatic drying feature for the heat exchanger after each cooling cycle to minimise this risk – a real bonus for those who tend to forget about manual maintenance.
Ignoring these signs is not just a matter of inconvenience. Most manufacturers make their manufacturer’s warranty conditional upon proof of regular servicing, documented by a service invoice. A compressor failure without a service history may therefore be charged in full, with the warranty not applying.
What Facq offers:
Facq supplies systems from brands renowned for the reliability of their after-sales service in Belgium and for features that make routine maintenance easier. The Samsung WindFree range incorporates Auto Clean and Freeze Wash technologies, which ensure that the indoor heat exchanger is automatically dried and cleaned between cycles.
Once you have chosen a system, maintenance is an integral part of the project, not a separate consideration. Our guide Home air conditioning: how to choose the right system? explains how to choose the right system before going into detail about how to look after it over the long term.
Frequently asked questions
Q1. How often should you clean your air-conditioning filter?
Every two to four weeks during the heating season. A dirty filter can increase electricity consumption by 10 to 20 per cent and significantly reduce comfort levels – yet it only takes ten minutes to clean.Q2. Is an annual leak test legally required in Belgium?
No, not for the vast majority of domestic split-system air conditioners. The F-Gas Regulation requires this check for systems containing 5 tonnes of CO₂ equivalent or more, which is approximately 7.4 kg of R32. A standard single-split system contains 1 to 3 kg of refrigerant, which is well below this threshold. Servicing is still recommended for performance and warranty purposes, but is not a legal requirement at this refrigerant charge level.Q3. What happens if I never have my air-conditioning serviced?
Efficiency gradually declines, with a loss of up to 20 per cent over two to three seasons. The unit’s lifespan is reduced from 15–20 years to less than 10 years, and the manufacturer’s warranty may be refused in the event of a breakdown if there is no documented record of servicing.Q4. How much does an air-conditioning maintenance contract cost in Belgium?
Expect to pay between €100 and €200 a year for a residential single-split system; this amount increases with the number of indoor units in a multi-split system. This is significantly cheaper than replacing a compressor, which often costs between €400 and €800.Q5. Can you top up your air-conditioning refrigerant yourself?
No, never. Handling refrigerant, regardless of the quantity, is strictly reserved for F-gas-certified professionals. This is a legal requirement with no significant exceptions, unlike periodic leak checks.Q6. Does a ducted air-conditioning system require different maintenance?
Routine filter maintenance remains the same, but access for professional inspection requires an access panel to be fitted at the time of installation, as the unit is concealed within a suspended ceiling. Without this access panel fitted in advance, maintenance becomes more complicated and more expensive.