Furnace limit switches are wired in series with which component?

Furnace limit switches are essential safety devices that monitor the temperature within the furnace and ensure it operates within safe limits. When the furnace overheats, the limit switch opens, cutting power to the gas valve and shutting off the gas supply to the burners. This is a critical function to prevent potential hazards such as overheating or fire.

By being wired in series with the gas valve, the limit switch plays a vital role in controlling the flow of gas to the burners. If the limit switch engages due to a high temperature, it effectively interrupts the power supply to the gas valve, preventing any further gas from being released, which is paramount for safety.

In contrast, components like the blower motor, transformer, or thermostat are not directly interrupted by the limit switch in this way. The blower motor is typically controlled by the thermostat to manage airflow, while the transformer provides the necessary voltage to operate the system. Thus, only the gas valve is impacted directly by the limit switch's safety mechanism.