The submerged electrode low water cutoff used in some automatically fired auxiliary boilers, will secure the burner fuel supply if the boiler water level __________. See illustration MO-0047.
• Submerged electrode low water cutoff operation in an automatic boiler • How water conductivity allows current to flow between the electrode and the boiler shell • What happens to the control circuit when the water no longer bridges the gap to the electrode tip
• In this design, when is the control circuit completed: when the electrode is covered by water or when it is dry? • If the purpose is to protect the boiler from damage due to low water, should the burner keep firing when the electrode is exposed or when it is submerged? • Looking at the illustration, where is the lowest point at which water must be present to keep the burner permissive circuit energized?
• Identify which part of the illustration represents the electrode tip and which part is the boiler shell (ground) • Decide at what exact water level the electrical path through the water is broken • Eliminate any answers that describe a condition that would be unsafe for boiler protection (i.e., would allow firing with dangerously low water)
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