What is a coil, and where do you find them in your air conditioning system? A coil is an arrangement of pipes and thin pieces of aluminum used to either transfer heat from hot refrigerant to the outside air (the condenser coil) or to transfer cold from cold refrigerant to the inside air (the evaporator coil). Both work the same way.

    A coil is a series of pipes, (usually copper), looped in a back and forth pattern to create as much surface area as possible for the coolant to pass through. To increase the transfer of temperature, thin, closely spaced, aluminum plates are attached to the tubes, which help pull the heat or cold out of the pipes. A fan pulls air across the greatly increased surface area and maximizes the transfer. The evaporator coil is the most obvious part of the outside portion of your AC unit, while the condenser coil is not usually visible without removing a door on the inside air handler.