Which condition indicates incomplete combustion in an oil burner?

The indication of incomplete combustion in an oil burner is best represented by the presence of yellow or orange flames. In a properly functioning oil burner, combustion should ideally produce a blue flame, which signifies complete combustion. The presence of yellow or orange flames suggests that not all the fuel is being burned efficiently, often due to a faulty air-to-fuel ratio. This inefficiency results in the formation of soot or carbon particles, which produce the yellow or orange coloration.

While other conditions may signal problems with the burner, they do not specifically indicate incomplete combustion as directly as the flame color does. For instance, black smoke indicates a rich fuel mixture but is not the only outcome of incomplete combustion. Excessive noise might stem from various mechanical issues rather than combustion efficiency. Fluctuating oil pressure can affect burner operation but does not solely point to combustion effectiveness. Therefore, the observation of yellow or orange flames is the most accurate indicator of incomplete combustion in an oil burner.