Cleaning and Maintenance of Fan Coils – Filters, UVC Lamps, and Regular Service

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Cleaning and maintenance of fancoils – how to handle filters, UVC lamps and regular service

A fancoil is a device that continuously moves air – heated or cooled – during operation. Every hour, it filters dozens to hundreds of cubic meters of air from the room, and this fact makes regular maintenance an absolute necessity, not just a recommendation. A dirty filter reduces air flow, overloads the motor, increases electricity consumption and – most importantly – dramatically worsens indoor air quality. On the wet fins of the heat exchanger, mold and bacteria begin to multiply. The condensation drain tray gets clogged and causes water damage. In practice, we often deal with the consequences of neglected maintenance, and it is always more expensive and complicated than if a three-minute filter check had been done in time.

In this article, we will systematically cover the entire topic of fancoil maintenance: from types of filters, through cleaning the heat exchanger and drain tray, to modern UVC disinfection lamps, service schedule and specifics for different types of installations. If you are looking for information on selecting the device itself or on installation, see our related articles How to choose a fancoil – performance, type of mounting and number of pipes and Installation of a fancoil – procedure, connection and commissioning.

Why fancoil maintenance is critically important

A fancoil is not a passive device like a radiator. It has moving parts (fan), wet parts (heat exchanger, tray) and air parts (filter, inlet grid). Each of these areas requires a different form of care and a different inspection interval.

A 50 % clogged filter typically causes a 30–40 % drop in air flow. This means that the heat exchanger receives less air, condenses more moisture on it, the fins remain wet for longer and become a breeding ground for microbiological growth. At the same time, the fan motor tries to compensate for the resistance of the clogging by increasing its power – it can overheat and its lifespan can be shortened. In extreme cases, we also see freezing of the heat exchanger in cooling mode, because the air flow is too low to keep the surface of the heat exchanger above the freezing point.

From a hygiene perspective, the situation is even more serious. The filter captures dust, fibers, pollen, mites and other biological contaminants. If it remains full, it stops filtering and becomes a source of contamination itself – bacteria and mold multiply on it and the air passing through it becomes contaminated instead of being cleaned. The result is seen in offices, hotels or healthcare facilities as increased illness rates, unexplained fatigue among staff and customers, or an odor coming from the units. These are typical signs of neglected maintenance.

Types of filters in fancoils – what, where and why

Most fancoils use a primary mechanical filter, which is located directly at the inlet grid or in the intake part of the unit. Its main task is to protect the heat exchanger from coarse dirt – dust fibers, larger particles and other mechanical impurities that would clog the fins of the heat exchanger.

Coarse mechanical filter (G3/G4)

This is the standard filter in most fancoils intended for residential and office use. Class G3 or G4 captures particles larger than 10–50 micrometers. It is made of polypropylene or glass fibers, in some cases of metal mesh, and is usually washable and reusable. The cleaning interval depends on the dustiness of the environment – in a normal office, we are talking about every 4–6 weeks, in an industrial environment this interval can be as short as 1–2 weeks.

Fine filters (F5–F7) and HEPA

Some premium fancoils or special applications (healthcare, clean rooms, allergy sufferers) require finer filtration. Filters F5–F7 capture smaller dust particles including pollen and parts of biological aerosols. HEPA filters (H13–H14) are capable of capturing 99.97–99.99 % of particles larger than 0.3 micrometers including most viruses and bacteria. These filters are used less in standard fancoils – they require a higher pressure difference and a stronger fan – but in combination with UVC technology they form a very effective hygiene barrier.

Carbon (activated carbon) filter

Captures chemical and odor contaminants – cigarette smoke, VOC (volatile organic compounds) from furniture, paints and cleaning products, as well as some biological substances. Carbon filters are installed after the mechanical filter and have limited lifespan – they become saturated and need to be replaced, not cleaned. Typically they are replaced once every 6–12 months depending on the load.

Inlet grids and intake kits

The inlet grid is the first line of defense and also what the customer sees most. For built-in IVAR SLI DC 400 fancoils, a special intake kit for IVAR.SLI DC 400 is designed, which integrates the inlet filter and ensures proper air flow direction. For the larger model, there is also available inlet grid for IVAR.SLI DC 600 – both are designed to be easily removable, cleanable and reinserted without tools. This simple replaceability is crucial in practice – if filter cleaning is time-consuming or requires unit disassembly, people delay it and eventually don't do it at all.

Step-by-step filter cleaning procedure

Filter cleaning is the most common and simplest maintenance task that can be done even by a layperson. Here is the exact procedure on how to do it correctly:

Preparation and safety

Before any manipulation with the fan coil, turn it off – ideally via the thermostat or control system. If you are working at height (cassette or ceiling units), disconnect the electrical terminal block or switch off the circuit breaker. Never clean the filter while the fan is running – this not only poses a risk of injury, but also risks drawing dust deeper into the system.

Removing the filter

Most floor-standing and semi-embedded IVAR SL/SLI fan coils have the filter accessible after sliding or opening the inlet grid. The procedure is: open or unscrew the inlet grid (in most models it is 2–4 screws or plastic clips), and carefully slide the filter outward. Do not shake it – inside the room you may disperse the trapped contamination into the air.

Cleaning

Polypropylene and metal filters (classes G3/G4) can be cleaned as follows:

Vacuuming: Use a vacuum cleaner with a soft brush to go over the surface of the filter from the side that draws in air (the side facing out of the unit). This is the gentlest method suitable for every cleaning interval.
Water rinse: For more intense dirt, rinse the filter under running warm water – also from the side where the air comes in (i.e., remove dirt in the direction of flow, not against it). Never use hot water or aggressive cleaning agents – they can damage the filter fibers.
Drying: Let the filter dry completely before reinstallation! A wet filter in the unit is an ideal breeding ground for mold. In practice, lay it on a clean mat and let it dry for at least 30–60 minutes at room temperature, or gently blow it dry with compressed air.

Reinstallation and inspection

Check the seal around the filter – the filter must fit so that air flows only through it, not around it. Any gap reduces the filtration efficiency to zero in the area of that gap. Reattach the grid and turn the unit back on. Check whether the airflow corresponds to the expected level (compare with your memory or measurements before cleaning).

Cleaning the heat exchanger and fins

The filter protects the heat exchanger, but not completely – dust particles, grease and biological substances settle directly on the fins of the heat exchanger. At the same time, during cooling mode, moisture condenses on the heat exchanger, which washes the trapped contamination into the drip tray, but part of it remains on the fins. After 2–3 years of operation without cleaning the heat exchanger, the condition of the fins can become critical.

Cleaning the fins of the heat exchanger is a more demanding task and is usually part of the professional annual service. Procedure:

Clean the fins with a soft bristle brush (nylon) in the direction of the fins (vertical or horizontal, not perpendicular – you may bend them)
Apply a special foaming cleaner for HVAC fins – these preparations are pH-neutral and do not damage aluminum or copper. Let it act for 5–10 minutes and rinse with condensate (i.e., let the system run and the condensate will rinse the heat exchanger) or with a gentle stream of water
For strong biological contamination (visible mold, black spots) it is necessary to apply a biocidal preparation approved for use in air conditioning and heating systems

Important warning: The fins of the heat exchanger are very delicate – the thickness of the fin is typically 0.1–0.15 mm and the fin spacing is 1.2–2.5 mm. Any mechanical action across the fins bends them and permanently reduces the performance of the heat exchanger. There are special combs (fin comb) to straighten bent fins, but it is a time-consuming job and it is always better to prevent damage.

Condensate tray – an underestimated problem

The condensate tray (drip tray) collects water that condenses on the heat exchanger during cooling. This water contains minerals (limescale), organic substances and biological contaminants. If the tray is not regularly cleaned, two scenarios may occur: clogging of the drain and overflow of the tray (water damage), or biological contamination of the stagnant water (legionella, mold).

We see both scenarios in practice. Clogging of the drain is typical with long-term neglect – biological matter accumulates in the drain pipe, completely blocking it. If the fan coil is installed in a suspended ceiling above a space (e.g., an office, hotel), an overflow of the tray can cause significant damage to the drywall structures, electrical installation and equipment in the space. We have seen such damages in the value of tens of thousands of euros – just because the tray was not cleaned during preventive maintenance.

Cleaning the tray: Drain the stagnant water, clean the tray with a damp cloth and mild cleaning agent, check and clean the drain pipe (blow into it or push through with a wire), and at each service, rinse the drain pipe with a disinfecting solution. Some professional systems have an installed UV light directly in the drain or biocidal tablets directly in the tray.

UVC lamps in fan coils – principle, types and correct operation

UVC radiation (wavelength 200–280 nm, optimally 254 nm) destroys the DNA of microorganisms – bacteria, viruses, mold and mites – and thus disinfects the air and surfaces of the heat exchanger and tray. This technology has existed since the 20th century, but it became more widespread in fan coils only in recent years, partly due to increased attention to indoor air quality after the COVID-19 pandemic.

How a UVC lamp works in a fan coil

The UVC lamp is located inside the fan coil, typically just behind the filter or in front of the heat exchanger, or above the condensate tray. The radiation directly UV-C irradiates the air passing through the unit, and at the same time disinfects the surface of the heat exchanger and tray – which are precisely the places where biological contaminants prefer to settle and multiply. The effectiveness depends on the intensity of the radiation, the length of the irradiated section and the speed of air flow (slower flow = longer exposure time = higher disinfection efficiency).

For IVAR SL and SLI 400 fan coils, a specially developed UVC lamp for IVAR.SL, SLI 400 with a length of 475 mm is available. This lamp is precisely dimensioned for the internal space of these models, ensuring optimal coverage with radiation without unwanted shadows or unirradiated zones.

Safety when working with UVC lamps

UVC radiation is dangerous for human tissue – it causes skin burns and eye damage to the retina already after a few seconds of direct exposure. When working with a fan coil that has a UVC lamp installed, the lamp must be turned off. Never look directly at a lit UVC lamp. Well-designed systems have an interlock – the lamp automatically turns off when the unit cover is opened. If you don't have such an interlock, switch off the power at the circuit breaker before any work.

Lifespan and replacement of UVC lamps

A standard UVC tubular lamp (low-pressure mercury discharge lamp) has a nominal lifespan of 8,000–12,000 hours, which corresponds to 2–3 years of operation at 12 hours per day. However, the intensity of UV radiation starts to decrease much earlier than the lamp physically fails – after about 6,000–8,000 hours, the intensity may be reduced by 20–30%, which significantly reduces the disinfection efficiency. Therefore, it is recommended to replace the UVC lamp every 2 years regardless of whether it is still lit.

Old UVC lamps contain mercury and must be disposed of as hazardous electrical waste – not in regular waste.

Regular Service Schedule – What, When, and Who

Based on practical experience, we recommend the following minimum service schedule. Naturally, intensively operated equipment in dusty environments (production, gastronomy, industry) requires shorter intervals.

Monthly (owner / operator – layman maintenance)

Visual inspection of the filter – clean if visibly dirty
Check the inlet and outlet grilles – cleanliness, no damage
Check the condensate tray in cooling mode – verify that the drain is working
Check the regulation and thermostats – verify proper function

Quarterly (technically skilled operator)

Cleaning of the filter (even if it does not look dirty visually)
Cleaning and disinfection of the condensate tray
Cleaning of the drain pipe
Check the fan noise level – change in noise indicates bearing failure or imbalance
Check the electrical connections (terminal blocks, regulation)

Annually (qualified service technician)

Professional cleaning of the heat exchanger fins (fine foam + rinse)
Chemical disinfection of the tray and drain
Check and, if necessary, replace the water connection gasket (risk of corrosion, micro-leakage)
Measuring the temperature of the refrigerant/water inlet and outlet and comparing with design values
Check the function of thermostats and regulation – recalibration if there is a deviation
Check the electrical part – insulation resistance, contacts
Documentation of the unit condition

Every 2 years

Replacement of the UVC lamp (even if it is still lit – intensity is lower)
Check and, if necessary, replace the filter material if it is damaged
Revision of the entire wiring system (for larger installations)

Regulation and its impact on service requirements

The type of fancoil regulation directly affects the frequency and scope of required maintenance. Simple on/off regulation causes frequent starting and stopping of the fan, which leads to higher mechanical stress on bearings and higher current pulses during startup. Smooth DC INVERTER regulation operates practically continuously at low speeds, which is much more gentle on the motor – but at the same time, it means that air is passing through the filter continuously, and the filter gets dirty more evenly and possibly faster than in intermittent operation.

If your fancoil has 4-speed control, you can regulate when it will need service. Regulation for IVAR.SL, SLS – built-in 4-speed 230V allows direct setting of fan speed, which is practical when setting up operation so that air flow is optimal in relation to the degree of filter clogging – at low speeds, the flow is lower and the filter gets dirty more slowly, while at high speeds, the flow is higher and the filtration efficiency is higher. The topic of regulation is discussed in more detail in our article Regulation of fancoils – from a simple switch to smooth DC INVERTER regulation.

Maintenance specifics according to installation type

Floor-mounted and semi-embedded (built-in) fancoils

These types are the most convenient from a service point of view – the filter and grille are usually accessible without a ladder, at a height of 0–80 cm from the floor. Built-in fancoils (installed under a window sill or in a floor duct) may have limited access to the filter due to the building structure, so it is important to consider service space during installation design. We recommend at least 30 cm of free space in front of the inlet grille, ideally 50 cm. For built-in variants, we also recommend an installation box for air conditioners and fancoils, which facilitates installation and future service access – the box integrates space for electrical installation and allows cleaner condensate drainage.

Ceiling cassette fancoils

Access to the filter is from below through the cassette panel. The filter can usually be removed without tools, but working overhead and at height is less convenient. The condensate tray in cassettes is critical – if it overflows, the damage falls directly onto the space below the cassette. We recommend a significantly shorter inspection interval for the tray – every 2 months during active cooling operation.

Wall-mounted fancoils

Access to the filter is usually through the front panel, and the filter is easily removable. Condensate usually drains through a hose leading outside or into the sewer. Checking the drain is simple – it is sufficient to visually verify that the hose is not kinked or clogged.

More about installation types and their specifics can be found in the articles Built-in vs. wall-mounted fancoils – which solution is suitable for my project and Dimensions and installation requirements of IVAR SL, SLI and SLS fancoils.

Typical mistakes in fancoil maintenance – from practice

Over the years of customer service, we repeatedly encounter the same mistakes, which usually have predictable and unnecessary consequences:

Cleaning the filter with a damp cloth without drying: The filter is returned to the unit wet, resulting in intense contamination with mold within 1–2 weeks. Always dry the filter before reinstallation.
Ignoring the tray when only the filter is checked: The filter is clean, so "everything is fine". Not really – the tray has clogged the drain and is waiting for the first cooling season to overflow.
Cleaning the fins across the fibers with a brush: Bent fins reduce performance and repair is time-consuming. Always clean in the direction of the fins.
Leaving the UVC lamp on during service: The technician opens the unit, the lamp is on – risk of eye and skin injury. Always turn off the power before opening the cover.
Skip service when the unit is "working": The unit is running, air is blowing, the temperature is apparently correct – but the fins are dirty, the tray is a biological bomb, and the performance is 40 % of the design. The unit does not make noise until the problem is big.
Using aggressive cleaning agents: Bleach or alkaline cleaners can corrode aluminum fins and cause corrosion that breaks the fins and causes leaks. Use only products specifically designed for HVAC systems.

Maintenance record and documentation – why it pays off

We recommend keeping a simple maintenance record for each fan coil in the building – whether it is one unit in an apartment or twenty units in an office building. The record should include: date of service, what was done, filter condition (visual rating scale), condition of the drip pan, any anomalies (noises, odors, visible damage), and the name of the person who performed the service.

Why? In the case of a malfunction or complaint, the service history is a key document. When selling real estate, it increases its value. And practically – if you know when the filter and UVC lamp were last replaced, you don’t have to guess and risk unnecessarily.

For larger projects (hotel, administrative building, industrial facility), keeping a maintenance record is required by hygiene regulations – equipment that moves air on a larger scale is subject to legislative requirements for regular inspection and documentation of its condition.

What to do in case of suspected biological contamination

If you detect an odor (musty, earthy, chemical) from the fan coil, or if someone in the space reports allergic reactions, coughing, irritated skin or eyes, it is necessary to act quickly:

Turn off the fan coil (you can let it run in ventilation mode without heating/cooling for a short time if ventilation is needed, but preferably not)
Have a specialist perform a microbiological swab of the surface of the heat exchanger and the drip pan
Ensure professional disinfection – the biocidal product must be on the list of approved biocides for HVAC systems (e.g. products based on hydrogen peroxide, quaternary ammonium compounds or chlorine dioxide)
Check and possibly replace the UVC lamp
Consider installing a finer filter (F5–F7) and shorten the cleaning interval

In the case of confirmed presence of Legionella pneumophila (bacteria causing legionellosis), the procedure is much more extensive and is governed by legislation – the equipment must be shut down, and the operator is required to report the finding to the health department.

Most frequently asked questions – FAQ

How often should the fan coil filter be cleaned?

In a typical residential or office environment, we recommend a visual inspection every month and physical cleaning every 4–6 weeks. In dustier environments (manufacturing, restaurant, near a construction site), cleaning may be needed as often as once every two weeks. A good indicator is monitoring air flow – if it seems that the fan coil is blowing less than usual, the filter is likely clogged. A clean filter costs nothing other than a few minutes of time and significantly extends the life of the unit.

Can I keep the UVC lamp turned on continuously?

Most UVC lamps designed for fan coils are dimensioned for continuous operation simultaneously with the fan coil – they run when the fan is running. Some systems have the UVC lamp connected via a fan interlock contact, so it automatically turns off when the fan coil is off. From a safety perspective, it is appropriate to wire the UVC lamp in this way – so that it does not emit light when the unit’s cabinet is open or when someone is performing service. Continuous operation naturally shortens the lamp’s nominal lifespan – with 24/7 operation, replacement may be needed after 12–18 months instead of 2 years.

Is it necessary to service the fan coil even if it is heating, not cooling?

Yes, and for several reasons. The filter gets clogged regardless of the operating mode. The heat exchanger fins get dirty with dust deposits, which can become a breeding ground for microorganisms when humidity is present (switching to cooling mode). The drip pan is not working intensively during heating, but old contamination from the cooling period can remain in it. Heating operation does not eliminate the need for service – it just changes slightly the nature of what needs to be checked. Service before and after each heating season is an ideal double annual plan.

What does increased noise level from the fan coil indicate?

A change in noise – whether it is higher noise, vibrations, knocking or whistling – is always a signal that needs to be addressed. Higher air noise typically indicates a clogged filter or a mechanical blockage at the air inlet/outlet. Vibrations may indicate a loose fan or its imbalance (worn bearings, foreign object in the fan circuit). Whistling at startup or at low RPM may indicate damaged bearings, which should be checked and possibly the entire fan motor replaced during the next service. More on fault diagnosis can be found in the article Common fan coil faults and how to eliminate them.

Can I use a regular household cleaner to clean the heat exchanger?

No. Regular household cleaners (toilet gel, bleach, alkaline degreasers) are either too aggressive for the aluminum fins of the heat exchanger or leave residues that can emit odors or react with materials when heated or cooled. Use only products labeled as suitable for HVAC and heating heat exchangers – these are pH-neutral, evaporate quickly or are easily rinsed with condensate, and do not damage metal or plastic.

How long does a professional annual service of one fan coil take?

For a standard built-in or floor-standing fan coil with access to the filter, heat exchanger and drip pan, we are talking about 30–60 minutes of work by an experienced technician. It includes filter cleaning, chemical cleaning of the heat exchanger (application and rinse), disinfection of the drip pan and drain, electrical check, control check and possible documentation. Ceiling-mounted units or built-in units in hard-to-reach locations may take longer. When replacing the UVC lamp, add another 15–20 minutes. An annual service of an entire hotel with 40 fan coils typically takes 2–3 working days for a pair of technicians.

Conclusion – regular maintenance always pays off

A fan coil is a device that can work trouble-free for 15–20 years with proper maintenance. Without maintenance, the same fan coil can become a source of hygiene problems and energy inefficiency within 2–3 seasons, and a source of more serious faults within 5–7 years. The cost of preventive service is a fraction of the cost of repair or replacement of the device, not to mention the damage caused by drip pan overflow or biological contamination of the space.

If you are looking for spare parts or accessories for your IVAR fan coils – filters, air grilles, UVC lamps or installation boxes – you can find everything in the fan coil category on atria.sk, where components are sorted by specific models. And if you are considering a new device, check out our article What fan coil capacity do I need for my room, where you will find a practical procedure for calculating the required capacity including tips from real customers.

Do you have a question about this topic?

Not sure or dealing with a specific situation in your home? Write to us – we are happy to help.