Patent ID: 7013841

Claim:
Water heating apparatus comprising: a fuel-fired water heater structure including a tank adapted to hold a quantity of water to be heated and having top and bottom ends, a jacket structure extending around said tank and defining therewith an insulation space that laterally circumscribes said tank, said jacket structure having a horizontal top end section extending over said top end of said tank and having a first opening and a second opening each extending downwardly through said top end section of said jacket structure, insulation disposed in said insulation space and extending between the outer side surface of said tank and the inner side surface of said jacket structure, a combustion chamber disposed beneath said bottom end of said tank, a fuel burner disposed within said combustion chamber, a flue extending from said combustion chamber, through the interior of said tank, to said first opening, and a combustion air intake passage extending through said insulation and intercommunicating said second opening and said combustion chamber, said fuel-fired water heater structure being useable as a natural draft water heater having a ready-to-use configuration in which said second opening is directly exposed to ambient air adjacent a top end portion of the natural draft water heater; and conversion apparatus, connectable to an upper end portion of said fuel-fired water heater structure, for converting said fuel-fired water heater structure to a selectively variable one of a power vented water heater structure, a natural draft direct vent water heater structure, and a powered direct vent water heater structure.