As many contractors attest, a supply air plenum is a sheet metal box attached to a furnace or air handler’s outlet and is used as a central manifold connector for other ductwork. As the air blows from the furnace or air handler, it flows through the supply plenum and any ductwork attached to it. The goal of such a measurement is to get an accurate reading of the air temperature leaving the HVAC equipment.
Measuring supply plenum temperature is a process that can become second nature to experienced HVAC contractors, but, for those first attempting or learning the trade, the action offers many pratfalls and potential obstacles.