Which type of control is provided on a boiler with an automatic/manual selector switch?

The scenario described involves a boiler equipped with an automatic/manual selector switch, which indicates a system capable of adjusting its operational mode depending on the requirements of the situation. Modulating fire control relates to the ability of the boiler to adjust the fuel supply (and thus the heat output) based on the current demand for steam or hot water.

In this mode, the system constantly monitors the pressure or temperature and modulates the burner firing rate accordingly. This ensures that the boiler operates efficiently, minimizing fuel consumption while meeting the specific heating demands. The modulating system allows for a gradual response to changes in load rather than simply turning the burner on or off, which is the main advantage of this control type in maintaining consistent performance and efficiency.

The other options do not adequately describe the full range of control delivered by the automatic/manual selector switch; they either suggest on-off control methods that lack flexibility or pressure control settings that do not account for the automatic modulation that modulating fire control provides.