New York Low Pressure Boiler Certificate of Fitness (COF) Practice Test

The stack switch is crucial in ensuring safety in a low-pressure boiler system by shutting off the burner in case of flame failure. This device monitors the temperature of the flue gases exiting the boiler. If the temperature drops below a certain threshold, indicating that the burner has failed to maintain a flame, the stack switch activates and automatically shuts down the burner. This prevention mechanism is vital to avoid potential hazards such as the buildup of unburned fuel or explosive conditions.

In contrast, while the vaporstat, gauge glass, and smoke detector serve important functions in monitoring and ensuring the operational status of the boiler, they do not play a direct role in shutting off the burner in response to a flame failure. The vaporstat, for example, is a safety device that monitors vapor pressure. The gauge glass is used to observe the water level within the boiler, and smoke detectors are primarily designed to alert for smoke presence, which may indicate issues but do not directly control the burner operation in the event of a flame loss.