The evaporator and condenser coils inside a central air conditioner or heat pump make it possible for these systems to complete the heat exchange process, which is the basis of refrigerated cooling and, in the case of heat pumps, heating. The coils form a loop and even though they’re continuous, each has a different function.
The Evaporator Coil
Located inside the blower compartment or air handler, the evaporator coil holds the chilled refrigerant that the compressor moves into it. As the air from the blower fan moves over the coil, the cold refrigerant removes the heat from your home’s air. The refrigerant becomes warmer and travels to the condenser coil outdoors.
With a heat pump, the process reverses in the winter and the evaporator coil expels heat from the refrigerant into your home instead of absorbing it and taking it outdoors. Most heat pumps have auxiliary heating elements that are part of the evaporator coil components to supply heat when temperatures fall below a certain point.
The Condenser Coil
This coil wraps around the periphery of the outdoor condenser and a large fan pulls air through it, helping the refrigerant inside the coil lose heat. If you’ve ever held your hand over the top or side of a condenser as it runs, you’ve probably felt the warm air blowing from it. The warmth comes from the heat the evaporator coil collected from your home.
A heat pump forces the evaporator coil to work as the condenser coil in the winter. Instead of losing heat, the condenser coil gathers it, the compressor pressurizes it and sends the hot refrigerant into the evaporator coil. The air blowing over the hot evaporator coil warms, increasing the temperature in your home.
Facts About the Coils
The engineering behind the evaporator and condenser coils is fairly complex and in order for you to achieve the highest level of energy efficiency and comfort, the coils need to be:
- Perfectly matched – Before you agree to purchase a new a/c system or heat pump, ask the HVAC contractor to verify that the coils match. It’s especially important in a split system, which is the most common type of residential HVAC equipment. If the condenser and evaporator coil don’t match perfectly, your energy costs will be higher and the system won’t perform as well. Ask for the certification documentation to verify the coils match each other.
- Clean – Both the evaporator and condenser coils perform best and their energy efficiency stays high when they’re kept clean. Anything covering the coils acts as insulation, retarding the heat exchange process. The condenser coil is fairly easy to clean by using a gentle spray from the hose and a soft brush. Keeping vegetation away from the outdoor condenser helps the coil cool faster, and redirecting grass clippings away from the condenser keep it cleaner.
The evaporator coil can be more challenging to clean since it may be difficult for you to access. If you can reach it, use a soft brush to remove the dust and be sure to keep the air filter clean. A clean air filter prevents dust from covering the coil. Because this coil causes water condensation during the cooling process, it’s vulnerable to mold or biofilm growth. Ultraviolet (UV) lights are an inexpensive way to keep the coil free of biological growths, which slow the cooling process.
- Leak-free – The coils can develop leaks over time, especially if either coil stays dirty for an extended period. When a coil leaks, it loses refrigerant in proportion to the size of the leak. Without enough refrigerant, the evaporator coil can freeze over, which stops the cooling process and may cause flooding and water damage when the frost melts. If your cooling system continues to run with a frozen coil, it can seriously damage the compressor, your system’s most expensive part.