What indicates that an oil burner is efficiently combusting fuel?

An efficiently combusting oil burner is characterized by a consistent flame color, which typically appears as a steady blue flame with minimal flickering. This color indicates that the fuel is burning completely and that the combustion process is stable, leading to optimal efficiency and reduced emissions. A consistent flame color suggests that the burner is properly tuned and the air-to-fuel ratio is balanced, ensuring that the combustion process is efficient.

In contrast, a high smoke reading would imply incomplete combustion, which results in soot formation and reduced efficiency. Low CAD cell resistance may indicate proper operation but does not specifically reflect combustion efficiency. Lastly, a net stack temperature of 600°F indicates potentially high waste heat, which could point to inefficiencies in the burner operation, as less heat should be lost through the stack for optimal performance. This further emphasizes why a consistent flame color is the strongest indicator of efficient combustion in an oil burner.