What is tested by disconnecting the Air Circulating Blower on a Force Warm Air Furnace?

When the Air Circulating Blower on a Force Warm Air Furnace is disconnected, it specifically tests the high limit control of the system. The high limit control is a safety feature that prevents the furnace from overheating by shutting it off when the temperature exceeds a predetermined safe threshold.

When the blower is disconnected, the heat generated by the furnace is no longer being distributed throughout the living space, causing the temperature within the heat exchanger to rise beyond normal operating conditions. If the high limit control is functioning correctly, it will activate, cutting off the gas supply to the burner and effectively shutting down the furnace to prevent overheating.

This test is crucial for ensuring that the safety mechanisms in the furnace are operational, as a failure in the high limit control could lead to dangerous situations, such as overheating or even a fire. Therefore, the action of disconnecting the blower directly assesses the responsiveness of the high limit control to unusual temperature conditions.