Evaporator Coil Fouling — Dust Accumulation in Air-Cooled Indoor Unit

Question

Accepted Answer

Exceeded air filter cleaning interval. Check: dust bypasses filter and adheres directly to fin surface What to do: Measure coil air velocity — normal 1.5–2.5 m/s; drops to 1.0 m/s or below when fouled. Without anemometer, check static pressure differential across filter Damaged filter (torn or gapped). Check: unfiltered air flows directly into coil What to do: Field cleaning: apply low-pressure washer (max 0.5 MPa) with alkaline foam coil cleaner, leave 10 min, then rinse in fin direction (top to bottom) Installation in kitchen or dusty environment. Check: greasy or fibrous dust tightly adheres to fin gaps What to do: For severe fouling, disconnect outdoor unit and remove coil for deep cleaning — reverse direction (against airflow) washing is most effective Dense coil (FPI ≥ 14) in dusty environment. Check: concentrated dust blocking What to do: After cleaning, inspect fin geometry — straighten bent fins with fin comb; restoring fins bent over 2 per cm² can recover 10%+ heat transfer performance Condensation during cooling operation mixes with dust forming sludge. Check: difficult to clean What to do: Replace filter and reset cleaning interval — every 2 weeks in dusty environments, monthly in normal environments

Evaporator Coil Fouling — Dust Accumulation in Air-Cooled Indoor Unit

Likely causes

Exceeded air filter cleaning interval

Damaged filter (torn or gapped)

Installation in kitchen or dusty environment

Dense coil (FPI ≥ 14) in dusty environment

Condensation during cooling operation mixes with dust forming sludge

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