Definition
An evaporator coil is the indoor heat exchanger of an air conditioner or heat pump, mounted atop a furnace or inside an air handler. Cold refrigerant in its tubes absorbs heat from air the blower pushes across its fins, and moisture condenses on the coil and drains away. In heat pump heating mode, the same coil releases heat instead.
Also called: Indoor coil, A-coil, Cased coil
Why it matters to you.
In a humid Central Kentucky summer the evaporator coil does the dehumidifying, so a dirty coil or weak airflow leaves rooms cool but clammy. Restricted airflow or low refrigerant charge can also freeze the coil, which shows up as ice on the refrigerant lines, water near the furnace and warm air at the vents.
Practical guidance.
Change filters on schedule, since restricted airflow is a common cause of a frozen evaporator coil. If you see ice on the coil or refrigerant lines, turn cooling off and let it thaw completely, then call for service; coil cleaning, leak testing and replacement are technician work.
About this definition
Written by the Feistritzer Heating & Air Conditioning team — family owned and operated in Danville since 1976, Kentucky HVAC license M02584. Definitions inform; a whole-system diagnosis in your home decides.