A plenum heater is an electric resistance heating device that is installed inside a ductwork system. The device gets its name from the point of installation, the plenum, which is the point where the furnace and ductwork joins together.
Plenum heaters work by heating air as it flows across the electric elements. This heated air is then distributed through the ductwork to the rest of the building. Plenum heaters convert fossil-fuel furnaces into dual-fuel systems and can help owners lower heating bills. Users who wish to use a plenum heater should contact a qualified HVCA contractor to ensure there is ample room in the plenum for installation.