When should a gas burner be fired in a steam boiler system?

Firing a gas burner in a steam boiler system is a critical step that must be performed with caution. The correct answer states that the burner should be fired after ensuring water is sufficient in the system. This is important because a steam boiler relies on adequate water levels to operate safely and efficiently. Insufficient water can lead to overheating and damage to the boiler components, as water acts as a coolant and a medium for steam production.

Additionally, maintaining proper water levels helps ensure that the steam produced is of the right quality and that pressure levels can be safely managed. Ignoring water levels can lead to dangerous situations such as boiler explosions or equipment failures. Therefore, the confirmation of sufficient water is a fundamental safety measure before ignition.

Other choices, while they contain some valid points, do not emphasize this crucial requirement as clearly. For instance, firing when water is above 50% capacity is not a safe standard on its own without ensuring that the total system water is adequate. Firing when boiler pressure is low does not guarantee the system is ready for operation, and purging lines is a separate safety procedure that does not address the necessity of sufficient water in the boiler before ignition.