Cleaning frequency

ASHRAE Standard 62.1 (Section 8, Operations and Maintenance) requires dehumidifying coils to be visually inspected for cleanliness and microbial growth regularly, 'but no less than once per year', and cleaned when fouling or microbial growth is observed; drain pans must be tested for proper drainage and filters maintained per the O&M manual. Although the standard targets buildings, a split performs exactly the same dehumidification on a coil that cannot be inspected without removing the cover. Annual sanitising is, in effect, applying this standard to the home.

ANSI/ASHRAE/ACCA Standard 180-2018 defines the minimum level of inspection and maintenance for HVAC systems in commercial buildings, including component task tables: coil cleaning, checking and cleaning drain pans and lines, filter replacement, fan checks. Typical frequencies are annual for coils and quarterly or semi-annual for pans and filters, depending on use. For Bucharest offices and shops with splits or cassettes, a maintenance contract aligned with Standard 180 is the correct professional reference.

EN 15780 'Ventilation for buildings – Ductwork – Cleanliness of ventilation systems' (also adopted as SR EN 15780 in Romania) sets three cleanliness classes by room use: low (storage), medium (offices, hotels, restaurants, schools) and high (hospitals, laboratories), with deposit assessment criteria and inspection intervals; specialist explainers cite annual inspection as the absolute minimum. The standard targets air-handling units and ductwork, but the principle 'inspect, measure deposits, clean when above threshold' also applies to split units in offices.

The Daikin FTXF-D manual states: 'it is recommended to have periodical maintenance performed by a specialist' and specifies that the unit must not be washed with water or chemicals by the user. This split of roles is standard across manufacturers: the user cleans filters and casing, the specialist cleans the evaporator, blower, pan and drain. Practical frequency in Bucharest: one sanitising per year for seasonal use, two per year (spring and autumn) for heavy use in both modes or homes with allergy sufferers, pets or smokers.

The DOE Energy Saver recommendation is to clean or replace filters 'every month or two during the cooling season', with extra attention when the unit runs constantly, in dusty conditions or with furry pets. Split manufacturers are stricter (2 weeks) because their mesh filters are smaller and clog faster. A realistic compromise for the customer: filters every 2–4 weeks during periods of use, plus a visual check of the outlet louvres for black spots.