I use the unit for heating in winter too – does autumn cleaning still matter?
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House in Chiajna, 12,000 BTU Daikin in the living room, we use it for cooling in summer and heating in winter (cheaper than electric heating at −2 °C). So it runs all year. Someone told me 'when heating, dirt doesn't matter because there's no condensation'. Is that right?
What is really happening
In heating mode the coils swap roles: the outdoor one extracts heat from the cold air and gets coated in condensate and frost, the indoor one releases heat into the room. What grew on the indoor evaporator over the summer dries out and becomes a dust of spores and biofilm fragments – dried mould remains allergenic – which the fan blows all winter in a closed house. Outside, clogged fins reduce heat exchange, the unit defrosts more often, and at −2 °C it loses exactly the capacity you want. That is why on an 'all-year' unit the rhythm is annual, in October, and with an intense summer, a second one in April.
- Read the manual and check accessible filters.
- Watch for leaks, unusual odours and noises.
- Request inspection if something is abnormal.
- Mould remains allergenic even when dead, so merely 'killing' it with a spray does not solve the problem – it must be physically removed. [US EPA, 2024]
- Spores deposited in air systems resuspend when the fan starts, which is why cleaning must remove them, not just inactivate them. [Science of The Total Environment, 2019]
- Fouling of the outdoor condenser raises pressure drop and condensing pressure, reducing the split unit's capacity and efficiency. [Science and Technology for the Built Env, 2019]
- Manufacturers recommend running the unit in fan-only mode for several hours to dry the interior before long periods of non-use, precisely to prevent odour and mould. [Daikin Europe, 2020]
What we do on site
- October: indoor unit with sealed double cover, alkaline detergent, adjustable pressure wash of evaporator, roller, pan and hose; sanitising; filters.
- Outdoor unit in the yard: washed in place, gentle on the fins; we check the drain holes at the base – in winter defrost water must get out or it freezes at the base.
- Visual check of the outdoor unit for leaves at the base and clearance (50 cm) – it matters more in winter.
- Test on 'Heat': warm air at the grille within 3–5 minutes, outdoor fan quiet. See current rates on the Prices page.
What you can do yourself
- Winter: filters monthly (dry dust, less than in summer, but blown straight into the room).
- Do not cover the outdoor unit with anything in winter if you use it for heating.
- Clear snow off and around the unit after snowfalls.
What NOT to do
- Do not skip cleaning because 'it doesn't matter in heating mode'.
- Do not put the outdoor unit under an eave where water drips – it freezes on the coil.
Prevention
Unit used all year: annual sanitising in October (between seasons); a second one in April if the summer was intense.
When to call us
0764 012 943, WhatsApp, Monday–Saturday 08:00–20:00; Chiajna is in our area.
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Sources (8)
- www.epa.gov/mold/mold-remediation-schools-and-commercial-buildings-guide-chapter-3
- www.sciencedirect.com/science/article/abs/pii/S0048969719347333
- onlinelibrary.wiley.com/doi/10.1155/2023/8984619
- www.tandfonline.com/doi/full/10.1080/23744731.2019.1605197
- www.researchgate.net/publication/233277421_Evaporator_Air-Side_Fouling_Effect_on_Performan
- www.daikin-ce.com/content/dam/document-library/operation-manuals/ac/split/ftxf-d/FTXF-D_Op
- web-manual.dit-daikin.com/ra/en/cleaning_filters/
- www.ashrae.org/file%20library/technical%20resources/standards%20and%20guidelines/standards
The information on this page is educational and based on cited sources; it does not replace medical advice. We do not do repairs, installation or refrigerant circuit work.