In a gas heating system, what does a high temperature limit switch do?

The high temperature limit switch plays a critical role in maintaining safety and efficiency in a gas heating system. Its primary function is to turn off the burner when the temperature exceeds a predetermined set point. This is crucial because excessive temperatures can lead to overheating, which poses a risk of damage to the heating system and potential hazards, such as fires or equipment failure. By shutting off the burner, the high temperature limit switch helps prevent these dangerous conditions and ensures that the system operates within safe temperature ranges.

The other options, while related to the operation of heating systems, do not accurately describe the function of the high temperature limit switch. Regulating gas pressure is typically managed by a gas pressure regulator, while sensing the temperature of flue gases may involve other safety devices but is not the primary function of the limit switch. Lastly, opening the gas valve during ignition is generally handled by the ignition control system rather than the high temperature limit switch. Therefore, the correct answer reflects the essential safety mechanism provided by the high temperature limit switch in gas heating systems.