Fluid-heating apparatus, circuit for heating a fluid, and method of operating the same

A fluid-heating apparatus for heating a fluid comprising:

• a heating element;
• and
• a control circuit configured to test for a dry-fire condition by
• detecting a first electrical characteristic of the heating element;
• powering the heating element after detecting the first electrical characteristic;
• removing power from the heating element;
• delaying a time period after removing the power;
• detecting a second electrical characteristic of the heating element after delaying the time period;
• and
• determining whether a dry-fire condition exists based on the detected first electrical characteristic and the detected second electrical characteristic.

A control circuit for a fluid heating apparatus, the control circuit comprising:

• a low-voltage power supply;
• a relay configured to couple one of a high-voltage power source and the low-voltage power supply to a heating element;
• a switch configured to couple the high-voltage power source to the relay;
• a sensor coupled to the low-voltage power supply and configured to detect an electrical characteristic;
• a controller configured to control the relay and the switch;
• and
• wherein the controller determines that a dry-fire condition exists based on the electrical characteristic.