Patent ID: 7706670

Claim:
A fluid-heating apparatus for heating a fluid, the fluid-heating apparatus being connectable to a first power source, the fluid-heating apparatus comprising: a vessel; an inlet to introduce the fluid into the vessel; an outlet to remove the fluid from the vessel; a heating element; and a control circuit applying a first electric signal to the heating element, determining a first value of an electrical characteristic based on the application of the first electric signal, applying a second electric signal to the heating element, the second electric signal being substantially different than the first electric signal, applying a third electric signal to the heating element, the third electric signal being substantially different than the second electric signal, determining a second value of the electrical characteristic based on the application of the second and third electric signals, determining whether a potential dry-fire condition exists based on the first and second values, and applying a fourth electric signal to the heating element if the potential dry-fire condition does not exist, the fourth electric signal being substantially different than the first and third signals.