Patent ID: 7256372

Claim:
A method of controlling a fluid-heating apparatus, the fluid-heating apparatus comprising a heating element for heating a fluid surrounding the heating element and a control circuit connected to the heating element and connectable to a power source, the control circuit comprising a current path from the power source to the heating element back to the power source, a switch connected in the current path, and a current sensor, the method comprising: initiating a heating state of the fluid-heating apparatus by establishing a current in the current path, the establishing act comprising making the switch to allow current in the current path; initiating a non-heating state and ceasing the heating state of the fluid-heating apparatus by ceasing the current in the current path, the ceasing act comprising breaking the switch to not allow current in the current path; applying a voltage to the heating element during the non-heating state; sensing a leakage current of the heating element during the application of the voltage; and determining a degradation of the heating element prior to a failure of the heating element with the sensed leakage current.