What component is wired in series with the high temperature limit switch in a conventional residential furnace?

In a conventional residential furnace, the component wired in series with the high temperature limit switch is the gas valve. This is because the high temperature limit switch serves as a safety device that monitors the temperature within the furnace. If the temperature exceeds a predetermined limit, the switch opens and interrupts the electrical circuit to the gas valve, effectively shutting off the flow of gas to the burners. This action prevents overheating and potential damage to the furnace, ensuring safe operation.

The gas valve must receive power in order to open for gas flow; thus, its operation is directly dependent on the state of the high temperature limit switch. If the limit switch is tripped due to excessive heat, the gas valve is de-energized, preventing further gas from being released and enhancing overall safety. This sequence is crucial in maintaining the furnace's safe functioning during operation.