What is the primary function of a roll-out limit switch?

The primary function of a roll-out limit switch is to monitor the temperature in the burner box. This device is designed to detect any abnormal increases in temperature that may indicate a malfunction within the combustion process, such as a blockage or improper air-fuel mixture. If the temperature exceeds a preset limit, the switch activates and typically shuts down the system to prevent further issues, such as equipment damage or hazardous situations like fires. This crucial safety measure helps ensure that the combustion appliances operate within safe thermal parameters, thereby protecting both the equipment and the space where it operates.

Other options can be considered in the context of HVAC systems, but they do not align with the specific purpose of a roll-out limit switch. Monitoring fuel levels or regulating combustion air directly relates to different components or sensors that manage fuel supply and air flow, while controlling the exhaust fan pertains to maintaining airflow but does not specifically involve monitoring temperatures in the burner box.