Abstract: A flow control device for an appliance having a burner, a blower, and at least one fuel valve for delivering a pre-mixed mixture of air and fuel to the burner includes a housing defining a passage through which the pre-mixed mixture of air and gas flows from the at least one fuel valve to the blower. A damper plate is rotatably mounted on the housing so as to control the flow of the pre-mixed mixture through the passage to the blower. The damper plate has an opening radially inward from its perimeter for allowing the pre-mixed mixture to flow therethrough.

Abstract: A heat exchanger for an apparatus including a burner has at least one tube extending along a centerline from an inlet end adjacent the burner to an outlet end. A plurality of indentations is formed in the tube adjacent the inlet end and extend radially inward towards the centerline. The indentations are formed in opposing pairs extending towards one another to a depth sufficient to create turbulent fluid flow through the inlet end of the tube.

Abstract: A heat exchanger for an apparatus including a burner has at least one tube extending along a centerline from an inlet end adjacent the burner to an outlet end. A plurality of indentations is formed in the tube adjacent the inlet end and extend radially inward towards the centerline. The indentations are formed in opposing pairs extending towards one another to a depth sufficient to create turbulent fluid flow through the inlet end of the tube.