With typical airflow obstructed, air that bypasses the filter may well carry Dust specifically to the evaporator coil and impair the coil’s heat-absorbing capacity. Filters can be found someplace alongside the return duct’s length. Frequent filter destinations are in walls, ceilings, furnaces, or in the air conditioner by itself. ... https://mytopfiles.s3.amazonaws.com/SignificanceofReverseCycleAirConditioning.html