1032 Duct Arrangement Allows Reverse Flow - Heating - Furnaces and Boilers -

Image Text: Cold air return > fan > existing down flow furnace (oil) > reverse flow of heat > add-on wood furnace > hot air plenum > heat > if the blower in the existing down flow furnace stops working, heat cannot rise out of the supply ductwork by natural convection > it flows backwards through the cold air return of the down flow furnace > this can damage the blower motor and belt as well as the furnace wiring > below floor ductwork