Is Your Ventilation Unit Ready for the Heating Season?
🔧 Tips on what to check before turning on the heating – ventilation unit filters, airflow balance, system tightness, heat exchanger and rotor belt.
The Start of the Heating Season – The Best Time to Check Your Ventilation Unit
During the colder months, we spend much more time indoors — that’s why having clean and healthy air is essential for everyday comfort and wellbeing.
Before the heating season starts, it’s worth making sure your ventilation unit (air handling unit) is running efficiently and supplying enough fresh air to every room.
Many homeowners only think about their system when they notice weak airflow or unpleasant odours, but you can easily prevent this with a few simple maintenance checks.
1. Replacing Your Ventilation Unit Filters – The Most Important Step
After the summer season, filters are often full of organic particles such as insects, fluff and pollen. These can start to decompose, cause unpleasant odours and reduce the airflow.
As the heating season begins, the type of air pollution changes – combustion particles from stoves, cars and smoke increase the amount of PM2.5 and PM1 fine dust in the air.
That’s why it’s recommended to use F7 class filters, and if you notice smoke odours, choose activated carbon filters for extra protection.
2. Airflow Balance and Duct Maintenance
Incorrect airflow can cause heat loss and affect indoor humidity levels. Turn on your ventilation unit and check if the supply and exhaust vents work evenly. If you notice weak air circulation:
- ✅ it’s time to replace the filters;
- ✅ or clean the ducts, especially on the exhaust side (usually the most contaminated);
- ✅ check the outdoor air grilles for leaves, fluff or insects – these can block the airflow.
💡 Tip: use additional filters on air valves to extend the lifespan of your main filters.
Extracted air DN100 valve 5xG3 Filter set
Ex VAT: 7.42 €
| Manufacturer of MVHR |
|
| Manufacturer | CleanFilter |
| Air handling unit | Exhaust air valve DN100 |
| Filter dimensions | DN100 |
| Class EN779 | G4 |
| Class ISO16890 | Coarse 65% |
| Protection level | Basic: larger solid particles, dust, fluff. |
| Quantity of filters | 5 |
| Advantages |
|
Extracted air DN125 valve 5xG3 Filter set
Ex VAT: 7.42 €
| Manufacturer of MVHR |
|
| Manufacturer | CleanFilter |
| Air handling unit | Exhaust air valve DN125 |
| Filter dimensions | DN125 |
| Class EN779 | G4 |
| Class ISO16890 | Coarse 65% |
| Protection level | Basic: larger solid particles, dust, fluff. |
| Quantity of filters | 5 |
| Advantages |
|
Extracted air DN150 / DN160 valve 5xG3 Filter set
Ex VAT: 10.40 €
| Manufacturer of MVHR |
|
| Manufacturer | CleanFilter |
| Air handling unit |
|
| Class EN779 | G4 |
| Class ISO16890 | Coarse 65% |
| Protection level | Basic: larger solid particles, dust, fluff. |
| Quantity of filters | 5 |
| Advantages |
|
3. Heat Exchanger Maintenance and Cleaning
Although filters capture most dust, the heat exchanger can still become dirty over time:
- ✅ if filters are not replaced regularly and impurities pass through the filter frame;
- ✅ or if ultra-fine particles enter the system.
Manufacturers recommend rinsing the condensate (non-enthalpic) heat exchanger every 1–2 years. It should remain clean and free of dust or grease to ensure maximum heat recovery efficiency. Enthalpic heat exchangers should only be cleaned carefully using a dry method to avoid damaging the membrane.
4. Plate Heat Exchanger Maintenance
Applicable units: Aerauliqa, Aldes, Brink, Blauberg, Brofer, Daikin, Dantherm, Helios, Holtop. Maico, Mitsubishi, Nibe, Paul, Pichler, Renson, Sabiana, Salda Smarty X, Soler&Palau, Vaillant, Vallox, Viessmann, Vent-Axia, Wolf, Zehnder, etc.
4.1 Condensate Drain System (for Condensing Heat Exchangers)
Condensate forms when there is a temperature difference between indoor and outdoor air, causing moisture to collect on the surface of the heat exchanger. The condensate system consists of a siphon and a drain tray.
It’s recommended to:
- Pour some water into the siphon to make it airtight and prevent air from entering the system.
- Clean the drain tray from dust and deposits.
If these parts are not maintained, water may start dripping from the unit’s casing or joints.
4.2 Outdoor Air Heater Maintenance (Pre-Heater)
If your system includes an outdoor air heater (heating coil), check its surface — without a protective filter it may be covered with dust or insects.
A dirty heater can produce a burnt smell when it switches on for the first time at the beginning of the heating season.
4.3 Bypass Damper Inspection
If your ventilation unit has a manual bypass damper, make sure it is fully closed.
For automatic models, check that the bypass operates in automatic mode and prevents warm indoor air from escaping outside.
5. Rotary Heat Exchanger Maintenance
Applicable units: Ensy, Flexit, Komfovent Domekt R, Salda RIRS/Smarty R, Systemair VTR/VSR, ÖSTBERG etc.
5.1 Rotor Belt Inspection
Inspect the belt: if it’s cracked or damaged, replace it immediately.
Check the tension – a loose rotor belt can cause noise and reduce heat transfer efficiency.
5.2 Rotor Brush and Seal Condition
If the rotor brushes or sealing gasket are worn out, it can cause an internal air leak — extracted air and odours may return to the supply side.
In this case, these components should be replaced immediately.
6. Energy Saving and Ventilation Settings
This mode helps save electricity while maintaining a comfortable indoor climate.
Conclusion: Prepare Your Ventilation Unit Now and Breathe Clean Air All Winter
- A well-prepared ventilation unit helps save energy and maintain a healthy indoor climate at home.
- Clean filters = less dust, better sleep, and lower energy bills.
- It’s best to replace filters in advance — so you don’t have to stop the system or open windows in the middle of winter.
Why Choose Cleanfilter Filters
- ✅ Certified quality according to ISO 16890 tests – ensures clean indoor air.
- ✅ Hygienic VDI 6022 certified filters made from German material, free from PFAS compounds.
- ✅ Best price directly from the manufacturer’s warehouse – no middlemen.
Wolf CWL-2-325/400 1xF7 Filter (Smog&Pollen)
Ex VAT: 19.94 €
| Manufacturer of MVHR | WOLF |
| Manufacturer | CleanFilter |
| Air handling unit |
|
| Filter dimensions | 245x510x22 |
| Class EN779 | F7 |
| Class ISO16890 | ePM1 70% |
| Protection level | High: fine particles, dust, pollen, mold spores, combustion particles, smog particles, insecticide dust. |
| Quantity of filters | 1 |
| Advantages |
|
| Manufacturer product number | 1669552 |
| Remarks | Supply air filter. Extract air filtration requires an additional G4/M5 filter, available in our shop. |
Blauberg KOMFORT EC SB 350 F7+G4 Filter set (Efficient)
Ex VAT: 19.01 €
| Manufacturer of MVHR | Blauberg |
| Manufacturer | CleanFilter |
| Air handling unit | KOMFORT EC SB 350 |
| Filter dimensions | 500x196x40 |
| Class EN779 | F7+G4 |
| Class ISO16890 | ePM1 70% |
| Protection level | High: fine particles, dust, pollen, mold spores, combustion particles, smog particles, insecticide dust. |
| Quantity of filters | 2 |
| Advantages |
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Paul Novus 300/450 1xF7/AC Activated carbon filter (Odor)
Ex VAT: 15.78 €
| Manufacturer of MVHR | Paul |
| Manufacturer | CleanFilter |
| Air handling unit |
|
| Filter dimensions | 180x475x50 |
| Class EN779 | F7/AC |
| Class ISO16890 | ePM2.5 60% |
| Protection level | Particles and odors: fine particles, dust, pollen, mold spores, combustion particles, volatile particles, NOx, O3 gases. |
| Quantity of filters | 1 |
| Advantages |
|
Domekt R 250 F / R 400 F (up to 2021-03) 1xF7/AC Activated carbon...
Ex VAT: 18.72 €
| Manufacturer of MVHR | Komfovent |
| Manufacturer | CleanFilter |
| Air handling unit |
|
| Filter dimensions | 278x258x46 |
| Class EN779 | F7/AC |
| Class ISO16890 | ePM2.5 60% |
| Protection level | Particles and odors: fine particles, dust, pollen, mold spores, combustion particles, volatile particles, NOx, O3 gases. |
| Quantity of filters | 1 |
| Advantages |
|
| Remarks |
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ENSY AHU 300 Ceiling 1xF7/AC Activated carbon filter (Odor)
Ex VAT: 15.55 €
| Manufacturer of MVHR | ENSY |
| Manufacturer | CleanFilter |
| Air handling unit |
|
| Filter dimensions | 140x240x94 |
| Class EN779 | F7/AC |
| Class ISO16890 | ePM1 70% |
| Protection level | Particles and odors: fine particles, dust, pollen, mold spores, combustion particles, volatile particles, NOx, O3 gases. |
| Quantity of filters | 1 |
| Advantages |
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| Manufacturer product number | 1460-860 |