In a modulating control system, what is the firing rate adjusted proportional to?

In a modulating control system, the firing rate is adjusted proportional to the steam load. This means that as the demand for steam increases or decreases, the control system modulates the firing rate of the burner or boiler to match that load. This is essential for maintaining system efficiency and responding dynamically to changes in the steam requirements of the system.

When the steam load is high, the control system increases the firing rate to generate more steam to meet the demand. Conversely, when the steam load decreases, the firing rate is lowered to prevent excess steam production, which can lead to inefficiency and potential safety issues. This proportional control helps ensure that the steam supply is both stable and responsive to the operational needs of the system.

The other options do not directly influence the firing rate in the same specific manner as the steam load. While factors like fuel supply, water temperature, and air pressure all play crucial roles in overall boiler operation, it is the steam load that directly dictates how much fuel is needed at any given time in a modulating system.