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
An electrician is performing a continuity test on a 3-conductor cable and gets a reading between the black and white conductors. This indicates:
Answer: A short circuit between the conductors — the cable must be replaced
Continuity between black and white conductors in a de-energized cable indicates an insulation failure or direct short that requires cable replacement.
During routine maintenance, a licensed electrician discovers that aluminum conductors are connected to a CO/ALR-rated receptacle using push-in (backstab) terminals. The correct action is to:
Answer: Rewire to the screw terminals — backstab terminals are not rated for aluminum conductors
CO/ALR receptacles permit aluminum connections only via screw terminals, not push-in backstab connections, which are unreliable with aluminum.
A variable frequency drive (VFD) repeatedly faults on 'output phase loss.' The motor and cabling test good. Where should the electrician look next?
Answer: Output contactor or terminal connections between VFD and motor
If the motor and cable test good, the output phase loss fault usually points to a loose connection or failed output contactor between the VFD and motor.
A ground fault indicator on a 480V delta system is glowing on one phase. What does this indicate?
Answer: A ground fault on that phase, changing voltage relationships to ground
On an ungrounded delta system, a single ground fault causes the affected phase to read near zero to ground while the other two glow bright on indicator lights.
An electrician is troubleshooting a lighting system where half the fixtures in a series of fluorescent fixtures are out. The most efficient first step is to:
Answer: Check voltage at the first dead fixture to determine if power is present
Checking voltage at the first dead fixture identifies whether the problem is upstream (no power) or within the fixtures themselves, guiding all subsequent steps.
After replacing a failed motor, the new motor runs hot and draws higher-than-nameplate current at no load. What should be checked first?
Answer: Whether the motor shaft can be turned freely by hand before energizing
High no-load current and heat with a new motor often indicates a mechanical binding issue; verifying free rotation before energizing is essential.
A licensed electrical contractor is testing a newly installed service entrance for proper operation. Which test verifies the main bonding jumper is correctly installed?
Answer: Verifying continuity between the neutral bus and equipment grounding bus in the main panel
The main bonding jumper connects the neutral bus to the equipment grounding bus in the service equipment; continuity between them confirms it is installed.