What mechanism in pilot systems typically ignites the main burners?

The thermocouple plays a critical role in pilot systems by serving as a safety device and ignition source for the main burners. When the pilot flame is lit, the thermocouple generates a small voltage that is a result of the temperature difference between its hot and cold junctions, thanks to the Seebeck effect. This voltage keeps the gas valve open, allowing gas to flow to the pilot and subsequently the main burners.

In addition, the thermocouple must reach a certain temperature to maintain its voltage output, ensuring that the pilot flame is continuously present. If the pilot flame were to go out, the thermocouple would cool down, stop producing voltage, and consequently close the gas valve to prevent any gas from escaping, enhancing safety. This mechanism underscores the importance of the thermocouple in the process of igniting the main burners, as it effectively combines the roles of monitoring and controlling the system.

Other options like the thermopile, flame sensor, and switch relay have different functions. The thermopile generates a higher voltage used for powering controls but does not directly ignite the burners. The flame sensor detects the presence of a flame rather than initiating ignition itself. The switch relay is involved in controlling the flow of electricity but does not provide