[The Newell]

Let me also ad Raritan water heaters are extremely simple and basic. There is no thermister or thermocouple or anything else. The tank and the electrical portion of all Raritan water heaters are remarkably similar to residential electric water heaters, and they work the same way

The thermostat on Raritan water heaters is basically a simple automatically resetting bimetallic element that presses against the OUTSIDE of the metal tank. When the water inside the tank heats, the metal tank itself also heats up to the same temperature. As the heat from the metal tank transfers to the back side of the thermostat, it opens and closes, sending power to, or cutting power off from, the electric resistance heating element.

If the bimetallic thermostat should go bad and stick in the "on" position, sending continuous power to the heating element, the thermostat has a safety backup, which is another bimetallic element, that "pops" at somewhere around 195 degrees F. killing the power to the heating element.