What is the primary function of a fan/limit switch in a furnace?

The primary function of a fan/limit switch in a furnace is to react to changes in temperature. This component serves two main purposes: it controls the operation of the blower fan and monitors the temperature within the furnace.

When the furnace reaches a certain preset temperature, the limit switch activates the fan to circulate heated air throughout the living spaces. Conversely, should the temperature exceed a safe limit, the limit switch will cut off the burner to prevent overheating, ensuring that the furnace operates safely and efficiently.

This temperature-driven operation is crucial for maintaining comfort and safety in HVAC systems. It allows the system to adapt to the heating needs based on the indoor temperature, preventing temperature-related issues such as overheating.

In contrast, other options pertain to functions that are not the primary role of the fan/limit switch. Regulators for gas flow, blower speed controllers, and flue gas monitoring are typically managed by different components within the HVAC system, each designed for their specific roles.