Red Seal Gasfitter — Class A Practice Exam

What is the purpose of a thermocouple in a gas appliance?

1. To regulate gas pressure

2. To detect whether the pilot light is on and to cut off gas supply if it is not

3. To measure the temperature of the gas

4. To control the flow rate of gas

The correct answer is: To detect whether the pilot light is on and to cut off gas supply if it is not

The purpose of a thermocouple in a gas appliance is primarily to detect whether the pilot light is on and to cut off the gas supply if it is not. This component functions as a safety device that provides an essential role in ensuring that gas does not continue to flow in case the pilot flame goes out. When the pilot light is burning, the thermocouple generates a small voltage due to the heat from the flame, which keeps the gas valve open, allowing gas to flow. If the pilot light goes out for any reason, the temperature drops and the thermocouple stops producing the voltage. This drop in voltage signals the gas valve to close, effectively shutting off the gas supply and preventing the risk of a hazardous gas buildup. This safety feature is crucial in gas appliances, as it ensures safe operation and helps prevent accidents related to gas leaks. In this context, the role of the thermocouple aligns specifically with the safety measures required in gas appliances rather than with regulating pressure, measuring temperature, or controlling flow rates.