Licensed Electrical Contractor Troubleshooting & Maintenance 3

Question 1

A lighting circuit dims noticeably when a large appliance starts. What is the primary cause?

Accepted Answer

Excessive voltage drop due to undersized wiring or loose connections

Answer

Shared neutral overloaded

Answer

Phase imbalance at the panel

Answer

AFCI breaker restricting current

Question 2

When troubleshooting a tripped thermal-magnetic breaker, you find the breaker is warm but the circuit is lightly loaded. What should you suspect?

Accepted Answer

A loose connection at the breaker lug causing resistance heating

Answer

The breaker is correctly sized for the load

Answer

The ambient temperature in the panel is too high

Answer

The circuit neutral is open

Question 3

A 120V outlet measures 105V under load and 118V at no load. This is best described as:

Accepted Answer

Excessive voltage drop indicating a wiring problem

Answer

Normal voltage regulation

Answer

Utility supply issue requiring a call to the power company

Answer

Neutral current feedback from adjacent circuits

Question 4

During PM on a motor control center (MCC), you find carbon tracking on the bus insulation. The correct action is to:

Accepted Answer

De-energize, clean with appropriate solvent, and inspect for the arc source

Answer

Apply insulating varnish over the tracking

Answer

Continue operation and schedule repair at next maintenance window

Answer

Apply electrical tape to isolate the affected area

Question 5

A circuit breaker fails to trip during an overload test. The most appropriate action is to:

Accepted Answer

Replace the breaker immediately — a breaker that won't trip is a fire hazard

Answer

Adjust the trip setting upward to compensate

Answer

Verify the test equipment is calibrated and retest

Answer

Reset and return to service; test errors are common

Question 6

What does a 'hot-cold' pattern on a thermal imaging scan of a switchboard indicate?

Accepted Answer

A potential loose connection or overloaded conductor at the hot spot

Answer

The switchboard is operating normally with load variation

Answer

A calibration error in the infrared camera

Answer

A voltage unbalance from the utility supply

Question 7

A 3-phase panel shows a neutral conductor that is significantly hotter than the phase conductors. What is the most likely cause?

Accepted Answer

High harmonic content from non-linear loads overloading the neutral

Answer

Oversized neutral conductor increasing reactance

Answer

Phase-to-neutral fault on one circuit

Answer

Incorrect phasing of 240V circuits