Patent ID: 6246831
Filing Date: 2001-06-12
Classification: F24H,G05D,H05B

Abstract:
A fluid heater powered by an alternating current (AC) electric power source, said heater comprising:a housing having at least one chamber, said housing having a fluid inlet and a fluid outlet;a plurality of electrically powered heating elements, each of said plurality of heating elements positioned within a respective one of said at least one chamber for heating a flowing fluid;a power controller for controlling the connection of each of said plurality of heating elements to the AC power source such that each of said plurality of heating elements is connected for at least one half cycle of each of the plurality of power cycle patterns defining a power level, the plurality of power levels at which said plurality of heating elements operate are selected from the group consisting of 0/2x, 12.5/2x, 25/2x, 37.5/2x, 50/2x, 62.5/2x, 75/2x, 87.5/2x and 100/2x, wherein a numerator of each of these fractions represents the number of half cycles of an x Hz AC power source within one second during which said plurality of heating elements are powered, wherein the operation of each of said plurality of heating elements is sequentially timed to substantially reduce switching frequencies which otherwise would cause visually perceptible lighting flicker from the AC power source;one or more fluid temperatures sensors each responsive to fluid temperature at a selected location within the at least one chamber; anda logic circuit for controlling a desired temperature of the flowing fluid from the fluid outlet, said logic circuit receiving temperature information from the one or more fluid temperature sensors and providing temperature information to said power controller.