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
Clark County and Portland-metro homes that add central air or a heat pump to an existing furnace need an evaporator coil installed on the furnace, matched to the new outdoor unit and its refrigerant. A dirty filter or low airflow can ice the coil during a heat wave, leaving 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 run the fan only, then call for service; coil cleaning, leak testing and replacement are technician work.
About this definition
Written by the Home Energy Group team — a family-owned HVAC company celebrating 25 years of comfort & care across SW Washington and the Portland metro, licensed in Washington (WA LIC# HOMEEGI003J7) and Oregon (OR CCB# 184255). Definitions inform; an on-site diagnosis decides.
