How is the air-to-fuel ratio adjusted in an oil burner?

In an oil burner, the air-to-fuel ratio is adjusted primarily through the use of the air shutter or damper. This component allows for the regulation of the amount of air that mixes with the fuel prior to combustion. By opening or closing the air shutter, the operator can increase or decrease the airflow, thus altering the mixture of air and oil being burned. Achieving the correct air-to-fuel ratio is crucial for efficient combustion, which leads to optimal burner performance, reduced emissions, and improved energy efficiency.

While other options relate to burner operation, they do not specifically address the adjustment of the air-to-fuel ratio in the same direct manner as the air shutter or damper. For instance, modifying the fuel pump rate impacts how much fuel is delivered but does not directly manage the air concerned. Similarly, the flame spreader primarily influences the distribution of the flame rather than the air-fuel mixture, and control board settings may include parameters that indirectly influence the air-to-fuel ratio but are not the main method for its adjustment.