A thermocouple is a device that’s made of 2 different strips of metal that are attached. It is installed so that its end is in the pilot light of the water heater burner. The thermocouple detects the heat from the pilot light.
Should the pilot light go out accidentally the thermocouple will automatically shut off the gas valve. This prevents gas from flooding the combustion chamber and causing an explosion.
The thermocouple performs its job through a thermoelectric effect known as the Seebeck effect. This is when two separate types of metal in proximity to each other generate electrical voltage in proportion to the heat they sense. The higher the heat around the two metal pieces, the higher the voltage.
The thermocouple in a gas water heater is designed to keep the gas valve open through its electric voltage. If the pilot light goes out, the loss in heat causes the voltage between the two pieces of metal to drop, and this shuts the valve and reduces the combustion risk.
The thermocouple is a simplistic approach to water heater safety. When it begins to fail a replacement will be necessary. With our new sealed combustion chamber water heaters a call to your local Lee’s Summit plumbers at Advocate Master Plumbing would be wise.