RG(O) dual–fuel burner operates with gas or light oil on multi pass radiant or immersion tubes of approximately 4~6 inch ID. Ideally, the first leg of the tube should be at least 15 tube diameters in length. Longer tubes with additional legs should provide increased fuel efficiency. Shorter tubes can usually be fired satisfactorily if the burner is adjusted for faster mixing and the desired BTU. input is not too high for complete combustion within the tube. Straight tubes can also be fired successfully. Tubes larger than 6 ID may require special modification of the burner.