Air-gas curve in a modulating burner: servo, damper, and gas valve adjustment

In modulating burners, the air-to-gas ratio must remain correct throughout the entire power range, not just at the two extremes.

Servo and air damper

The servomotor moves the damper to change the air flow according to the load.

Gas valve

The gas supply follows a corresponding curve via actuator, linkage, or ratio control.

Intermediate points

Combustion must be checked at more than two points so that there are no areas with high CO or excessive O₂.

Final adjustment

The curve is confirmed using a flue gas analyzer and in accordance with the manufacturer's limits.