Water heater

A water heater including a water tank having an outside surface and a lower portion thereof, a burner producing hot combustion products located at or towards the lower portion of the tank, a casing around at least part of the outside surface of the tank and spaced therefrom so as to define a flue path within the casing and along the outside surface of the tank whereby combustion products can flow along the outside surface of the tank and can therefore heat water within the tank, the water heater further including at least one flow restriction located in the flue path and extending inwardly from the casing towards the outside surface of the tank and forming in generally horizontal section through the flue path a region of restricted flow area whereby the combustion products flowing along the flue path encounter the flow restriction and are restricted and disturbed in flow pattern at said at least one flow restriction, said at least one flow restriction being of limited vertical extent so that combustion products flowing past the flow restriction are again disturbed in their flow upon passing the flow restriction and encountering an increased flow area of the flue path past the flow restriction,

• wherein the tank has a cylindrical outside surface and the casing is cylindrical and defines a flue path around the entire circumference of the tank, and wherein said at least one flow restriction is a closed ring which extends inwardly from the casing so as to define a restricted flow area of annular shape in horizontal cross section through the flue path,
• wherein said at least one flow restriction extending inwardly from the casing towards the outside surface of the tank further has thereon a plurality of tank centering formations which contact the outside surface of the tank providing means for combustion products to flow past the at least one flow restriction so as to thereby locate and maintain the tank centered within the casing and so that the flue path is of uniform cross sectional shape wherever a horizontal cross sectional view therethrough is taken, wherein each of said centering formations comprises a projection which extends inwardly and contacts the outside surface of the tank at a point or small area contact zone.