Which condition would cause the temperature safety limit switch to shut off the burner?

The temperature safety limit switch is a critical safety component in a gas furnace that protects the system from overheating. When the temperature inside the heat exchanger exceeds a predetermined limit, the switch activates to turn off the burner, preventing potential damage or hazardous conditions.

A fan motor failure is particularly crucial. If the fan motor fails, the airflow through the furnace can be severely restricted or stopped altogether. This lack of airflow means that the heat produced by the burner cannot be effectively distributed throughout the home, causing the temperature within the heat exchanger to rise quickly. The temperature safety limit switch senses this excessive temperature rise and intervenes to cut off the burner, safeguarding the system and reducing the risk of overheating.

Other conditions, such as excessive gas flow, a blocked air filter, or low gas pressure, can lead to operational issues but do not directly trigger the temperature safety limit switch in the same immediate way as a failure in airflow due to fan motor issues. Excessive gas flow might cause a high flame but would not necessarily lead to the temperature exceeding safe limits immediately. A blocked air filter can restrict airflow, but the fan motor’s failure would render this condition much more critical. Low gas pressure affects burner operation but does not typically cause overheating by itself. Thus, it is the