What action does a limit control in a heating system perform?

A limit control in a heating system is designed to monitor and manage the temperature within the system to ensure safety and proper functioning. Its primary role is to prevent the system from overheating, which can lead to equipment damage or safety hazards. When the temperature exceeds a predetermined threshold, the limit control activates to turn the system off, effectively stopping the heating process. This action helps maintain a safe operating environment and protects both the heating unit and the surrounding area from potential damage.

In contrast, the other options do not appropriately describe the function of a limit control. While some components of a heating system may involve airflow or temperature adjustments, the specific action taken by the limit control is to react to high temperatures by turning off the system, making it an essential safety feature in HVAC systems.