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Filters

Daikin, Mitsubishi Electric, LG and Panasonic recommend cleaning the indoor unit's dust filters every 2 weeks. … and 3 more sourced claims.

Explanatory diagramA standard filter has limits
A standard filter has limits
  1. Particles of different sizes move through the air.
  2. The filter retains some particles, depending on its type.
  3. A standard filter is not equivalent to HEPA filtration or gas removal.

Particles are symbolic and not to scale.

strong evidenceDaikin, Mitsubishi Electric, LG and Panasonic recommend cleaning the indoor unit's dust filters every 2 weeks.

The user manuals converge: Daikin – 'it is recommended to clean the air filters every 2 weeks'; Mitsubishi Electric MSZ – 'clean every 2 weeks'; LG – 'clean the filter every 2 weeks'; Panasonic – 'once every 2 weeks'. The method is the same: vacuum or wash with water (below 50 °C for Mitsubishi, below 40 °C for Panasonic), dry in shade. Fine filters (deodorising, purifying) are cleaned every 6 months and replaced per the manual. This is the customer's safe DIY; everything behind the filters is the job of professional sanitising.

Sources (4)
moderate evidenceFine filters (deodorising, purifying) are cleaned about every 6 months and replaced every 6 months to 3 years, per the Daikin manual.

The Daikin manual specifies for the small filters: cleaning once every 6 months; replacement once every 3 years for deodorising filters and once every 6 months for air-purifying/dust-collection filters. It warns that dirty filters reduce deodorising capability and cooling and may cause odour. Many customers do not know their unit has these filters behind the large mesh and have never changed them. During sanitising the technician identifies them, cleans them or recommends replacement.

Sources (1)
moderate evidenceFilter efficiency and indoor particle concentration are the most important factors determining how fast the evaporator fouls.

LBNL (Siegel et al., 2002) concludes that 'the most important parameters in determining coil fouling times are the efficiency of the filter and indoor particle concentrations'. Split-unit mesh filters only capture large particles; fine dust, tobacco smoke, lint and pet hair pass through and stick to the wet fins. Hence in a home with pets, smokers or next to a dusty boulevard the evaporator loads much faster and sanitising may be needed twice a year. A torn or missing filter dramatically accelerates the process.

Sources (1)
moderate evidenceManufacturers prohibit benzine, thinner, scouring powder or insecticide on the indoor unit; only water and neutral detergent are allowed.

The Mitsubishi Electric, Panasonic and Daikin manuals carry the same prohibition: no benzine, thinner, polishing powder or insecticide on the indoor unit, only a soft cloth and neutral detergent (about pH 7), water below 40–50 °C. Reason: the casing plastic discolours or cracks, and aluminium fins and hydrophilic coatings corrode. For the same reason, aggressive solvent-based 'AC cleaner' sprays or chlorine solutions are unsuitable. Professional sanitising solutions are alkaline or neutral, formulated for aluminium, and fully rinsed.

Sources (3)

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