The international airports in Pennsylvania are Lehigh International Airport at Allentown, Erie International Airport at Erie, Harrisburg International Airport at Harrisburg, Philadelphia International Airport at Philadelphia,
Electric Plenum Heaters. A plenum heater is an electric resistance heating device that is installed in the plenum, which is the spot in the ductwork system where ducting and furnace join. Air is heated as it flows across electric elements and then is distributed through the existing ductwork.
1 These supply air plenums are sheet metal boxes that attach to the outlet of a furnace or air handler and are used as a central manifold for other ductwork to connect to. These return air plenums are the ducting that attach to a furnace for the return air to flow through, and are used as a central manifold for other return air ducting. 2  These sheet metal transition kits are used to make a custom fabricated duct to connect a new furnace or air hander to existing ductwork.