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.
Report Abuse. The plenum is the duct right on top of the furnace. A furnace has 2 ducts. Cold air is sucked-in through the return duct. The air is heated in the furnace and pushed through the plenum, which is the duct on top of furnace.Tam22 Â· 7 years ago. Thumbs up.he plenum is the sheet metal box on top of the furnace that connects the furnace to the rest of the duct work.