Question 65 UFIV01 - Chief Engineer - UFIV

The Correct Answer is B **Explanation for Option B (Correct Answer):** The problem states that a **low coolant water level alarm** is active, even though the water level in the expansion tank (where the sensor is presumably located) is **normal**. We are also told that the float-activated switch is designed to **open at low coolant level** to activate the alarm. This describes a "fail-safe" or "normally closed" (NC) circuit configuration, where the switch is normally closed (passing current) when the level is good, and it opens when the level is low. When the switch opens, it typically breaks the circuit to a relay coil, which then trips a set of normally closed alarm contacts, activating the alarm (or conversely, the opening of the switch activates the alarm circuitry directly). If the wire connections for the float switch are loose, the circuit path through the switch is broken (open circuit). An open circuit caused by loose wires mimics the electrical state of a **low coolant level** (which also opens the switch). Since the alarm is triggered by the switch being open, loose or broken connections will falsely activate the low level alarm, despite the coolant level being normal. **Explanation of Incorrect Options:** **A) The float level switch contacts are welded closed, not permitting the contacts to open.** If the switch contacts were welded closed, they would remain in the "normal level" state (closed). This would prevent the low level alarm from activating even if the coolant level *did* drop. It would prevent the *correct* alarm from sounding, but it cannot cause a *false* alarm when the level is normal. **C) The float is binding in the float chamber, not permitting the float to drop.** If the float is binding and cannot drop, the switch will remain in the "normal level" state (closed). Similar to option A, this would prevent a legitimate low level alarm from sounding if the level dropped, but it cannot cause a false alarm when the level is normal. **D) It is not possible for a low coolant level alarm to occur when the water level is normal.** It is entirely possible for a false alarm to occur due to sensor failure, electrical faults, or wiring issues, which is precisely what the question describes. This option is a definitive dismissal of common technical faults.