Before lighting a burner in a steam boiler, what must be ensured?

Before lighting a burner in a steam boiler, it is essential to ensure that there is water in the boiler. This is a critical safety measure because the presence of water is necessary to ensure proper operation and to avoid overheating the boiler components. If the boiler is lit without sufficient water, it can lead to serious damage such as overheating, warping, or even explosion due to extreme pressure buildup.

Maintaining an adequate water level ensures that the heat generated by the burner is absorbed safely and efficiently, allowing the steam system to operate reliably. Proper water level not only protects the boiler itself but also plays a vital role in the overall safety and performance of the steam system.

The other options relate to operational settings and procedures, which are important but secondary to the fundamental requirement of having water in the boiler before ignition.