Troubleshooting & Maintenance Flashcards
7 cards from real Licensed Electrical Contractor practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Troubleshooting & Maintenance flashcards as text
A submersible pump motor has failed megohmmeter testing. Before condemning the motor, you should:
Answer: Allow the motor to dry thoroughly and retest, as moisture affects readings
Moisture ingress in submersible motors dramatically reduces insulation resistance; the motor should be dried and retested before replacement.
A transformer secondary voltage is 10% higher than nameplate rating with no load. The most likely cause is:
Answer: Wrong tap setting on the primary side of the transformer
Incorrect primary tap settings change the turns ratio, directly affecting secondary output voltage — selecting a lower voltage tap raises secondary voltage.
When troubleshooting an intermittent ground fault on a large commercial system, the best systematic approach is to:
Answer: Divide the system in half repeatedly (half-split method) to isolate the fault section
The half-split method isolates intermittent faults efficiently by systematically eliminating half the system with each test.
During maintenance on a 480V motor starter, you find the contactor contacts are pitted and eroded. The correct maintenance action is to:
Answer: Replace the contact assembly — filed contacts reduce contact pressure and life
Contactor contacts should be replaced when worn, not filed; filing reduces thickness, changes geometry, and shortens remaining service life.
A 20A, 120V circuit is protected by a 20A AFCI breaker and also uses a GFCI outlet as the first device. A ground fault occurs downstream. Which device should operate first?
Answer: The GFCI outlet, as it is closest to the fault
The GFCI outlet closest to the fault should trip first due to its faster response to line-to-ground current imbalance at that point.
A licensed electrician finds an energized junction box with no cover during a maintenance inspection. According to the NEC, the immediate action should be:
Answer: Install an appropriate cover immediately or de-energize until covered
NEC 314.28 requires all junction boxes to have covers; an uncovered energized box is an immediate safety hazard requiring correction before leaving.
A circuit has 120V at the breaker but only 60V at the last outlet on the run. What is most likely the cause?
Answer: An open neutral creating a floating neutral voltage division
An open neutral in a 120/240V system causes floating neutral conditions where loads share 240V, resulting in abnormal voltages at outlets.