The function, maintenance of an air-conditioner's coil, fin and filter

An air conditioner cools with a cold indoor coil called the evaporator.

The condenser, a hot outdoor coil, releases the collected heat outside. The evaporator and condenser coils are serpentine copper tubing surrounded by aluminium fins. A pump, called the compressor, moves a refrigerant between the evaporator and the condenser.

The liquid refrigerant evaporates in the indoor evaporator coil, pulling heat out of indoor air and thereby cooling the surrounding area.

The hot refrigerant gas is pumped outdoors into the condenser where it reverts back to a liquid, giving up its heat to the outside air flowing over the condenser's metal tubing and fins.


An air conditioner's filters, coils, and fins require regular maintenance for the unit to function effectively and efficiently throughout its years of service. Neglecting necessary maintenance ensures a steady decline in air conditioning performance while energy use steadily increases.

Air conditioner filters

The most important maintenance task that will ensure the efficiency of your air conditioner is to routinely replace or clean its filters.

Clogged, dirty filters block normal air flow and reduce a system's efficiency significantly. With normal air flow obstructed, air that bypasses the filter may carry dirt directly into the evaporator coil and impair the coil's heat-absorbing capacity.

Keeping the filter clean can lower your air conditioner's energy consumption by 5-15 per cent. Most filters require cleaning every month or two during the cooling season.

Filters may need more frequent attention if the air conditioner is in constant use or is subjected to dusty conditions.

Air conditioner coils

The air conditioner's evaporator coil and condenser coil collect dirt over their months and years of service.

A clean filter prevents the evaporator coil from soiling quickly. In time, however, the evaporator coil will still collect dirt. This dirt reduces air flow and insulates the coil, reducing its ability to absorb heat.

To avoid this problem, check your evaporator coil every year and clean it as necessary.

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