Patent ID: 7814868

Claim:
Heating apparatus comprising: a fuel-fired heating appliance which, during firing thereof, discharges hot combustion gases through a flue; a housing having an internal wall structure dividing its interior into first and second chambers communicating with one another through an opening in said internal wall structure, said first chamber having an inlet area communicating with said flue to receive hot combustion gases therefrom, said housing further having an outlet area through which the received hot combustion gases may exit said housing; a draft inducer fan associated with said housing and operative to sequentially flow the received hot combustion gases from said first chamber through said internal wall structure opening into said second chamber and then outwardly from said housing through said outlet area; and a damper movable, by fluid pressure force created by operation of said draft inducer fan, from a normally closed position thereof in which said damper substantially prevents gas flow between said inlet and outlet areas, to an open position in which said damper permits gas flow between said inlet and outlet areas, said damper being a gravity damper pivotally carried within said housing for movement between said normally closed and open positions.