A non-bypassable catalyst assisted appliance (100, 1000) comprising; a housing (112, 1112) having a combustion chamber (300, 1300) therein; said housing having a loading door opening (117, 1117) coverable by a door (116, 1116) for loading fuel into said combustion chamber; said housing having a separate air inlet opening or a plurality of air inlet opening (1113; 1115) for receiving a primary air supply (P; P') and a secondary air supply (S; S') to said combustion chamber; said housing having an exit opening (118, 1118) connectable to a flue (119, 1119); a platform which operably forms a top surface of said combustion chamber and an upper wall of an air supply manifold operable for providing the secondary supply of air to the combustion chamber; a catalyst combustor (200, 1200) supported on said platform, said catalyst combustor having a catalytic combustor inlet (250; 1250) and a catalytic combustor outlet (252; 1252); a shroud (270; 1270) disposed around said catalytic combustor; wherein said non-bypassable catalyst assisted appliance (1000, 1000) does not include a movable catalyst bypass; wherein when said door of said non-bypassable catalyst assisted appliance is disposed in a closed position covering said loading door opening, gas from said combustion chamber is directed in a single flow path through said catalyst combustor, and out the flue with the single flow path of combustion gas passing through said combustor inlet of said catalytic combustor, between said platform and said shroud and through said catalytic combustor, out said catalytic combustor outlet of said catalytic combustor, and said exit opening into said flue; and wherein when said door of said non-bypassable catalyst assisted appliance is disposed in an open position allowing loading of fuel through said loading door opening to said combustion chamber, ambient air entering said loading door opening and gas from said combustion chamber are directed in a single flow path through said catalyst combustor, and out the flue with the single flow path of the combination of flow of ambient air and combustion gas passing through said combustor inlet of said catalytic combustor, between said platform and said shroud and through catalytic combustor, out catalytic combustor outlet of said catalytic combustor, and said exit opening into said flue. a housing (112, 1112) having a combustion chamber (300, 1300) therein; said housing having a loading door opening (117, 1117) coverable by a door (116, 1116) for loading fuel into said combustion chamber; said housing having a separate air inlet opening or a plurality of air inlet opening (1113; 1115) for receiving a primary air supply (P; P') and a secondary air supply (S; S') to said combustion chamber; said housing having an exit opening (118, 1118) connectable to a flue (119, 1119); a platform which operably forms a top surface of said combustion chamber and an upper wall of an air supply manifold operable for providing the secondary supply of air to the combustion chamber; a catalyst combustor (200, 1200) supported on said platform, said catalyst combustor having a catalytic combustor inlet (250; 1250) and a catalytic combustor outlet (252; 1252); a shroud (270; 1270) disposed around said catalytic combustor; wherein said non-bypassable catalyst assisted appliance (1000, 1000) does not include a movable catalyst bypass; wherein when said door of said non-bypassable catalyst assisted appliance is disposed in a closed position covering said loading door opening, gas from said combustion chamber is directed in a single flow path through said catalyst combustor, and out the flue with the single flow path of combustion gas passing through said combustor inlet of said catalytic combustor, between said platform and said shroud and through said catalytic combustor, out said catalytic combustor outlet of said catalytic combustor, and said exit opening into said flue; and wherein when said door of said non-bypassable catalyst assisted appliance is disposed in an open position allowing loading of fuel through said loading door opening to said combustion chamber, ambient air entering said loading door opening and gas from said combustion chamber are directed in a single flow path through said catalyst combustor, and out the flue with the single flow path of the combination of flow of ambient air and combustion gas passing through said combustor inlet of said catalytic combustor, between said platform and said shroud and through catalytic combustor, out catalytic combustor outlet of said catalytic combustor, and said exit opening into said flue.