Riello DB3 SM C03 Installation, Use And Maintenance Instructions page 51

5.5 Air/fuel adjustment
Fuel/combustion air is synchronized by means of a servomotor that, connected to a variable-profile cam, operates the outlet air
dampers and, by means of suitable linkage, the combustion head and gas butterfly valve.
To reduce pressure loss and to have a wider adjustment range, it is best to set the servomotor to the maximum output used, as
near to maximum opening (130°) as possible.
On the gas butterfly valve, the fuel's partial setting adjustment based on required output, with the servomotor fully open, is made
by using the pressure stabilizer on the train.
When setting the air/fuel ratio for the gas burners, the air and gas variable profile cams must be used, Fig. 26.
1 Cam
2 Adjustment screws
3 Fixing screws
4 Variable profile
5
CHAPTER
1 2
3
4
D1499
Preparation for start up
Fig. 26
21