Abstract: An air bypass system for use with a heating appliance that includes an outer enclosure and a combustion chamber enclosure positioned within the outer enclosure. The bypass system includes a first opening providing an air passage between a source of air from a remote location and an air space defined between the outer enclosure and the combustion chamber enclosure. The bypass system also includes a second opening providing an air passage between a source of room air and the air space, and an actuating member configured for movement between a first position substantially covering the first opening wherein the second opening is open for air flow, and a second position substantially covering the second opening wherein the first opening is open for air flow.