Gas water heaters utilize a pilot flame to light the main gas burner. If the pilot flame goes out, gas can be dangerously released. To prevent this, a thermocouple is used as a safety device to detect when the pilot light is burning. The tip of the thermocouple is placed in the pilot flame, generating a voltage which operates the supply valve that feeds gas to the pilot. As long as the pilot flame is lit, the thermocouple remains hot, and the pilot gas valve is held open. However, if the pilot flame goes out, the temperature of the thermocouple will drop and the electrical current will be disrupted. The gas supply will then shut off in response.
Thermocouples can be found at www.supplyhouse.com
