🔍 Key Concepts

• Conductivity-type water level electrodes in automatic boiler level controls • The relationship between electrode height and the sequence of control actions (pump start, pump stop, burner/fuel trip) as water level falls or rises • The safety function that must occur at the lowest water level compared with normal control functions

💭 Think About

• Look closely at the relative lengths of the three electrodes and note where the tip of electrode "C" is compared to the others. Is it the highest, middle, or lowest sensing point? • As boiler water level drops from normal toward dangerously low, which action must happen first to maintain level, and which action must happen last to protect the boiler from damage? Match those actions to the electrode positions. • Decide whether the function at arrow "C" is a normal control action (routine level control) or an emergency safety action. Which of the answer choices sounds like a safety shutdown rather than simple level regulation?

✅ Before You Answer

• Verify which electrode would logically be used to start the feed pump (this one should be lower than the pump-stop electrode but higher than any emergency shutdown electrode). • Identify which function must occur at the very lowest safe water level to prevent overheating of the boiler heating surfaces. • Before choosing, mentally trace what happens as water level moves down past each electrode tip and then back up again, and match each transition to one of the listed functions.