What factor primarily determines the rating of fuel oil burners?

The rating of fuel oil burners is primarily determined by the capacity of the air delivery system. This is because the efficiency and effectiveness of a burner are significantly influenced by the amount of air supplied for combustion. A properly sized air delivery system ensures that the correct air-to-fuel ratio is maintained, which is crucial for optimal combustion performance. An inadequate air supply can lead to incomplete combustion, resulting in poor efficiency, increased emissions, and potential safety hazards.

While other factors, such as fuel type and the size of the burner, do contribute to the overall functioning of the burner, they are not the primary determinants of the burner’s rating. Fuel type affects combustion characteristics, and burner size is essential for fitting the application, but without a sufficient and properly configured air delivery system, the burner cannot achieve its intended rating or performance level. Cooling efficiency is not directly related to the burning process, making it less relevant in determining the rating of fuel oil burners.