What is the purpose of a roll-out control in a furnace?

The purpose of a roll-out control in a furnace is fundamentally to enhance safety by preventing potentially dangerous situations, particularly those related to gas combustion. Roll-out controls are designed to detect excessive heat in the burner area, which can occur if there are issues such as clogged heat exchangers or other obstructions that impede the combustion process. When these controls identify runaway temperatures, they act to shut down the furnace, thereby protecting the system from damage and reducing the risk of fire or explosions.

Understanding the function of roll-out controls highlights the importance of monitoring for conditions that could lead to unsafe operation. This makes them critical components in ensuring that systems run safely and efficiently. The other options pertain to functionalities that are not directly related to the roll-out control's primary purpose, such as monitoring fan speed or controlling gas intake, which are typically managed by different components or systems within the furnace.