An electric forced-air heat system works by using electric elements to generate heat. Air is moved past these elements to warm it, and ductwork then distributes the heated air throughout the house. The forced-air system of distributing heat differs from gravity systems, which rely on natural air currents, and radiant systems, in which heated floors or walls are used to heat the room.
On receiving a signal from the thermostat, relays in the furnace begin the process of heating the elements. The elements are constructed from wire tightly wound into coils. When an electric current is applied to the coils, resistance to the current generates heat. Once the elements are hot, a fan turns on and forces air past them and then out to the house.
The forced-air part of the system refers to how the heated air is circulated. In this type of system, a fan is used to force the air through ductwork that distributes the warm air to each room. As the warm air enters a room, cooler air is displaced, and a separate system of ductwork returns the air to the furnace, where it is heated and sent out again. Forced-air systems help keep the air clean by routing the air through a filter as it circulates through the system.