One of the critical aspects of efficient air conditioing is the cleanliness of coils. In this note, we are going to go over the importance of a clean evaporator. The evaporator is also know as an “A” coil or indoor coil. It either sits above or below a gas furnace. If the system is a package unit or on an electric air handler, the evaporator will be inside the cabinet. As the blower moves air across the evaporator, the evaporator picks up heat out of the air. The heat is then transferred by refrigerant to the outside unit where the refrigerant is then condensed and cooled.