The evaporator coil is where the cooling magic happens. Cold liquid refrigerant enters the coil, expands into a gas, and absorbs heat from the air being blown across it. The cooled air goes to your home; the warm refrigerant gas travels to the outdoor condenser coil to dump that heat outside.
Where it sits
- In a gas furnace + AC system: directly above the furnace, in the supply plenum
- In a heat pump system: inside the air handler
- In a mini-split: inside the wall-mounted or ceiling-cassette indoor head
Common evaporator coil problems
- Frozen coil — restricted airflow or low refrigerant
- Refrigerant leak — formicary corrosion in 8-12 year old coils is common
- Dirty coil — reduces heat transfer, raises bills, eventually causes drain pan overflow
- Condensate drain clog — water backs up into the pan and overflows
Cleaning the evaporator coil is part of every annual AC tune-up. Replacement is a several-hour job involving refrigerant recovery and recharging.
Related: Condenser Coil, Refrigerant, TXV, Short Cycling.
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Right Way Mechanical is a family-owned HVAC contractor serving Wheat Ridge, Arvada, west Denver, and the Colorado foothills.