The evaporator coil is the indoor heat exchange component of a split HVAC system. Refrigerant flows through the coil at low pressure and temperature, causing it to absorb heat from the air passing over it. This process cools and dehumidifies the air before it is distributed through the ductwork.
The evaporator coil is housed inside the air handler or furnace cabinet. It must be matched to the outdoor condenser unit in both size and refrigerant type. A mismatched coil reduces efficiency, increases wear, and can void warranties.
Dirty evaporator coils are one of the most common causes of reduced cooling performance, frozen coils, and system failure. Coils should be inspected and cleaned annually. A clogged condensate drain line — which removes water collected by the dehumidification process — is also a frequent service issue.