Abstract: A removable dam provides a way to prevent liquid insulation from interfering with electrical components and from squirting out an opening in the jacket of a hot water heater.

Abstract: A water heater comprising a water tank and an electric resistance heating element extending into the water tank for heating water in the tank, including a proportional band temperature controller for conducting electric power to the electric resistance heating element in bursts, each burst of electric power followed by a period during which the temperature controller does not conduct power to the electric resistance heating element, wherein, each burst of electric power comprises about 95% or less of a cycle comprised of one burst of electric power followed by the period during which the temperature controller does not conduct electric power.

Abstract: An insulated tank construction for a water heater, including a cylindrical tank, a cylindrical shell placed around and spaced radially apart from the tank to form an annular space, and a ring-shaped form dam disposed circumferentially at a selected position in the annular space along the height of the tank. The foam dam is comprised of a resilient compressible material, preferably porous, open-cell polyurethane foam, and has an inner diameter less than the tank outer diameter and an outer diameter greater than the shell inner diameter. Thus, the foam dam is compressed into sealing engagement with both the tank wall and the shell wall. The shell inner wall, foam dam and tank outer wall form an annular chamber within the annular space. Expandable polymer foam material is injected into the annular chamber and expanded to form a jacket of insulating foam around the tank. Initially, gasses generated by expansion of the foam escape the annular chamber through the porous body of the foam dam.