How high must the center line of the flue outlet be above the burner port in a revertible flue furnace with a natural draft burner?

In a revertible flue furnace using a natural draft burner, the positioning of the flue outlet is crucial for ensuring proper ventilation and preventing backdrafts. The requirement for the center line of the flue outlet to be at least 12 inches (300 mm) above the burner port is designed to promote effective draft. This height allows for sufficient clearance, ensuring that combustion gases can rise and exit the flue efficiently without being obstructed by any nearby components.

Natural draft systems rely on the rise of hot gases to create a pressure differential that facilitates the outward flow of exhaust. If the flue outlet is positioned too low, it could disrupt this natural draft, leading to insufficient venting of combustion gases. This scenario can lead to safety hazards, such as the accumulation of carbon monoxide or other hazardous gases within the structure.

By adhering to the standard of at least 12 inches, compliance with safety regulations is maintained, ensuring that the flue operates effectively and safely. This height prevents any issues related to backdrafts and allows for proper functioning of the furnace, promoting both safety and efficiency.