Heating devices to prevent bacteria proliferation in the lowermost region of a water holding tank of an electric water heater
An electric water heater is described and wherein a bottom resistive heating element extends in at least a portion of the cavitated circumferential area defined inside the tank between the tank side wall and the dome-shaped bottom wall and wherein deposits accumulate to create a culture medium for bacteria growth. The bottom resistive heating element heats water in this cavitated area to a temperature sufficient to sanitize a lower region of said water holding tank and to kill bacteria such as the Legionella bacteria.
1 . An electric water heater comprising a water holding tank having a cylindrical side wall, a top wall and a dome-shaped bottom wall; a cold water inlet is disposed to release water under pressure in a lower portion of said tank, two or more resistive heating elements to heat water in an upper and lower region of said tank, a thermostat having a temperature sensor and a control associated with each said two or more resistive heating elements to control the operation of said resistive heating elements to heat water within said tank regions to pre-set desired temperatures, a cavitated circumferential area defined between a lower end portion of said cylindrical side wall and said dome-shaped bottom wall, and a bottom resistive heating element extending in at least a portion of said cavitated circumferential area to heat water therein to a temperature sufficient to sanitize a lower region of said water holding tank in the immediate area of said dome-shaped bottom wall.
2 . The electric water heater as claimed in claim 1 wherein said bottom resistive heating element is a low watt density resistive heating element having a partly circular shape and supported in said cavitated circumferential area and closely spaced to said dome-shaped bottom wall and said bower end portion of said cylindrical side wall.
3 . The electric water heater as claimed in claim 2 wherein said partly circular resistive heating element has opposed free-end sections each shaped as an upwardly extending goose-neck, a connecting flange secured to said free end sections for supporting said partly circular resistive heating element in said cavitated circumferential area in a substantially horizontal plane, said connecting flange having a sealed connection with an inner face of said cylindrical side wall about an opening for the passage of said free ends of said free end sections for immovable securement to an outer connecting flange assembly.
4 . The electric water heater as claimed in claim 3 wherein said outer connecting flange assembly is a dielectric connector assembly formed of a corrosion resistive material.
5 . The electric water heater as claimed in claim 2 wherein said lower watt density bottom resistive heating element when operated heats water in said cavitated circumferential area to a temperature of 140 degrees F. to sanitize said lower region of said water holding tank.