Fan Coils

A fan coil is an indoor component of a air conditioning or heat pump system. It is in effect an electric furnace or heater with an evaporator coil, a resistance heater, a blower, and a drain pan built inside. The electric heater provides heat on cold days and the evaporator supplies air conditioning on hot days. In heat pumps the coil supplies the hot air and the electric heaters act as supplemental or back up heat for very cold days when the heat pump is not enough to warm the space. The blower is used for both heat and cooling and also used for continuous fan operation.

An air conditioner not only cools the air but adds to the comfort level by dehumidifying or taking the moisture out of the air. Moisture condenses on the indoor coil like it does on the outside of a glass of ice water on a hot, humid day. As the warm air passes over the coil and is cooled it can't hold the same amount of moisture. The extra moisture is then carried away through the built in drain pan. From there it goes into a septic system or water trap. Sometimes the drain lines may become clogged which can result in water leaks in your ceiling or walls. An annual air conditioning inspection is a great way to keep your system is running smoothly and to keep drains clean.

The electric heaters or resistance heaters convert electricity directly to heat. Electric heat is often more expensive than heat produced by combustion appliances like natural gas, propane, and oil. Electric heaters circulate heat by blowing air which is supplied to the furnace through return air ducts across the heating elements. Blowers in electric furnaces move air over one to five resistance coils or elements which are usually rated at five kilowatts.

The heating elements activate one at a time to avoid overloading the electrical system. Overheating is prevented by a safety switch called a limit controller or limit switch. This limit controller may shut the furnace off if the blower fails or if something is blocking the air flow. The heated air is then sent back through the home through supply ducts.