EVAPORATOR COILS

During the cooling mode of the Air Conditioning system, a fan draws warm air from inside the home through a filter and the furnace and then over the evaporator coil. As the air passes over the coil, much of the moisture the air possesses is condensed and runs off into a drip pan where it is drained away through the drain lines. This process occurs because as the warm air passes over the coil, it is quickly cooled and can no longer hold the same amount of moisture as it did when it was warm. The refrigerant inside the evaporator coil enters as a liquid and once the warm, filtered air is passed over it, the temperature of the air is lowered. From here, the refrigerant carries the warm air as a gas to the outside compressor where the vapor is compressed and passed through the condenser’s coil. This process is much the same as what happens to a glass of cold water on a hot and humid day.

The main difference in evaporator coils are the shape and position of the coils within the cabinet. We prefer a horizontal slab coil for optimum heat removal and humidity control. A slab coil also allows for a coating of Bronz-Glow. We are certified applicators of Bronz-Glow. Bronz-Glow is a coating applied to the evaporator coil that contains an anti-microbial additive that will prevent the growth of mold and mildew eliminating “dirty sock” syndrome. The coating also prevents corrosion and electrolysis due to dissimilar metals.

The most important consideration for coil selection is the size relative to the condenser. Coil size determines the major balance between dry and wet heat removal.  The coil removes dry heat (temperature) and the wet heat (humidity).  The evaporator coil size determines this ratio.  A larger (than the tonnage of the condenser) evaporator coil is able to reach temperature settings faster and then shuts off the system as it satisfies the thermostat setting. However, the system is only able to remove moisture when it is running so the larger (than the tonnage of the condenser) coil removes less humidity. In many cases, a smaller coil can increase the humidity removal by 30% to 40% resulting in greater dehumidification; we select the evaporator coil with this in mind on the unitary single stage systems.

If you are having trouble with your heating or cooling system, click the button below to take a look at this list of simple, safe do-it-yourself diagnostic procedures.