Patent ID: 7817906

Claim:
A liquid heater comprising a chamber having an inlet and an outlet, and at least three electrodes within said chamber defining a plurality of adjacent channels for liquid flow from said inlet to said outlet whereby the liquid flow is divided between the channels and wherein the liquid is heated by electrical current flow through the liquid between two or more of said at least three electrodes; an electrical power supply connection; and at least one switch for each of said electrodes, the at least one switch being arranged to removably connect each of said electrodes to the power supply connection independent of the remaining ones of said electrodes, the electrodes being non-uniformly spaced apart from one another with different distances between different pairs of mutually-adjacent ones of the electrodes, so that connection of different sets of the electrodes to the electrical power supply connection provides different levels of current passing through the liquid, the levels of current including levels defining a stepwise progression between zero current when none of the electrodes are connected and a maximum current when all of the electrodes are connected, the progression having substantially uniform ratios between the currents of adjacent steps with non-zero current levels.