What must be present on the secondary low water fuel cut-out in a boiler with two low water fuel cut-outs?

The presence of a manual reset on the secondary low water fuel cut-out serves an important safety function in boiler operations. This requirement ensures that in the event of low water conditions, the system does not automatically reignite without the operator's acknowledgment. By requiring a manual reset, it mitigates the risk of the boiler operating under unsafe conditions, which could potentially lead to damage or hazardous situations. For instance, if the low water fuel cut-out is triggered due to inadequate water levels, the predefined requirement for a manual reset ensures that an operator assesses the situation and resolves any underlying issues before the boiler can restart.

The manual reset also emphasizes the importance of verifying that the water levels are back to safe operational parameters, adding a critical layer of safety in boiler management. Other options, while they may serve various functions in boiler operation and safety systems, do not specifically address the need for an operator to acknowledge a low water situation before resuming normal operations, making the manual reset a vital feature in the safety design of dual low water fuel cut-outs.