In premix and modulating burners, a zero governor or ratio regulator is often used so that the gas flow follows the change in air.
Zero governor
It maintains a specific pressure relationship and allows the venturi to essentially determine the gas flow through the negative pressure created by the air flow.
Ratio regulator
It maintains a ratio between two pressures, so that the gas flow follows the air flow.
Why it is important
The correct air-gas ratio maintains low CO, a stable flame, and good efficiency throughout the modulation range.
Adjustment
Final verification is performed using a flue gas analyzer and in accordance with the manufacturer's instructions.
