A service covers filters, both heat exchanger coils, the condensate drainage path, refrigerant pressures and electrical checks. Most of what degrades a system is airflow restriction and drainage blockage, both of which are cheap to prevent and expensive to ignore.
What degrades, and how fast
Filters
The indoor unit’s filters capture dust before it reaches the coil. As they load up, airflow drops. Reduced airflow over a cooling coil makes the coil colder, which can ice it up, which reduces airflow further – a feedback loop that ends with a unit that blows almost nothing and then trips. Filters are the single biggest determinant of performance and they are a user-cleanable item on most units.
The indoor coil
What gets past the filters lands on the coil fins, along with condensation. Dust plus moisture on a coil becomes a damp mat that restricts airflow and becomes a biological growth site – which is the origin of the musty smell people associate with air conditioning. A coil in that condition needs proper cleaning, not a wipe.
The condensate tray and drain
The same biological growth blocks drain lines. When the drain blocks, the tray overflows, and where the indoor unit is on a wall that means water down the wall – or, in a ducted or cassette installation, into the ceiling. It is the most common cause of visible damage from an air conditioning system and it is entirely preventable.
The outdoor coil
Leaves, grass cuttings, pollen and general debris clog the outdoor coil fins. A blocked condenser cannot reject heat, so operating pressures rise, efficiency falls and the compressor works harder and hotter. In a Norfolk garden in autumn this happens quickly.
Refrigerant charge
A sealed system should not lose refrigerant. If it is low, there is a leak, and topping it up without finding the leak is both an environmental problem and a waste of money – the same leak will empty it again.
What a service should include
- Filters removed, cleaned or replaced.
- Indoor coil inspected and cleaned properly, with a suitable coil cleaner rather than a cloth.
- Condensate tray cleaned and the drain line cleared and flow-tested, not just looked at.
- Condensate pump checked and cleaned where one is fitted.
- Outdoor coil cleaned and clearances around the unit checked.
- Fan motors and blades checked – an unbalanced outdoor fan is a common noise complaint.
- Operating pressures and temperatures measured, with the superheat and subcooling assessed to confirm the charge is correct.
- Electrical connections checked for tightness and signs of heat.
- Controls and modes tested, including the changeover to heating.
- Findings recorded, including the refrigerant type and charge.
A system that has stood idle all winter has a dry, potentially seized condensate path, dust on the coils, and no evidence it still works. Finding that out in April gives you weeks. Finding it out on the first hot day in July, when every firm in the county is booked, does not.
Refrigerant, leaks and the law
Refrigerants in most split systems are fluorinated greenhouse gases, and they are regulated. Two things follow from that for a householder.
- Only a qualified person may handle refrigerant. Recovering, charging or working on a sealed refrigeration circuit requires an individual handling qualification, and the business carrying out the work requires company certification. This applies to domestic systems, not just commercial ones.
- Deliberately releasing refrigerant is an offence. So is topping up a leaking system without repairing the leak. If a system is low on charge, the leak has to be found and fixed.
Domestic split systems are generally below the charge thresholds that trigger mandatory periodic leak checking – those apply to larger commercial systems. But the handling requirements apply regardless of size. The commercial obligations are covered in F-Gas compliance and in leak check frequency.
What you can do yourself
- Clean the filters – monthly in heavy use, and at minimum at the start and end of the season. Most units have a front panel that lifts to reveal them; they rinse in warm water and must be completely dry before refitting.
- Keep the outdoor unit clear. No leaves piled against it, no shrub growing across it, no bin in front of it. Clear airflow all round.
- Run it briefly in winter. Ten minutes of cooling once a month through the off season keeps the compressor oil circulating and the seals from drying out, and tells you it still works.
- Watch for water. Any dripping from an indoor unit is a drainage problem and should be dealt with before it stains a ceiling.
- Listen. New rattles, buzzes or changes in pitch from the outdoor unit are worth mentioning rather than getting used to.
Booking a service in spring costs the same as booking it in July and you will actually get a slot.
Questions we get asked about this
How often does air conditioning need servicing?
Annually for a domestic system in normal use, ideally in spring before the season. Heavier use, or a dusty or coastal environment, justifies more frequent attention – particularly filter cleaning.
Why does my air conditioning smell musty?
Biological growth on the indoor coil and in the condensate tray, which happens when they stay damp. It needs proper cleaning rather than an air freshener, and it usually comes with a partly blocked drain that is worth dealing with at the same time.
Water is dripping from the indoor unit.
The condensate drain is blocked, or the tray has been displaced, or a condensate pump has failed. Turn it off and have it seen to – the next stage is water running down a wall or into a ceiling.
My unit is not cooling as well as it used to.
Most often dirty filters or a blocked outdoor coil – both restrict airflow and both are cheap to resolve. If those are clear, it may be low on refrigerant, which means a leak that needs finding rather than a top-up.
Can I top up the refrigerant myself?
No. Handling refrigerant requires an individual qualification and the business doing it requires company certification. And a system that needs topping up has a leak, so a top-up is not a repair.
Should I run it in winter?
Briefly, yes – ten minutes of cooling every month or so keeps the compressor oil moving and confirms the system still works. Many modern units also have a self-dry function worth using at the end of each cooling session.
Regulations and standards referenced on this page
- Regulation (EU) No 517/2014 on fluorinated greenhouse gases, as retained and amended in GB law — UK Statute Law Database
- Fluorinated gases (F gases): guidance for operators and engineers — Environment Agency / Defra
What happens when you call
Call and describe it
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