Licensed Electrical Contractor Electrical Contractor Troubleshooting & Maintenance 2

Question 1

A 240V circuit is reading 120V at the outlet. What is the most likely cause?

Accepted Answer

Open neutral on the circuit

Answer

Tripped GFCI upstream

Answer

Undersized wire gauge

Answer

Faulty breaker handle

Question 2

When troubleshooting a motor that hums but does not start, which component should be checked first?

Accepted Answer

Start capacitor

Answer

Run capacitor

Answer

Thermal overload

Answer

Contactor coil

Question 3

What does a megohmmeter reading of 0.5 MΩ on a 480V motor winding indicate?

Accepted Answer

Failed insulation requiring immediate attention

Answer

Normal insulation resistance

Answer

Acceptable but marginal insulation

Answer

The megohmmeter is malfunctioning

Question 4

During thermal imaging of a panelboard, one breaker shows significantly higher temperature than adjacent breakers carrying similar loads. What is the most probable cause?

Accepted Answer

Loose connection at the breaker terminal

Answer

Normal operating variation

Answer

Oversized conductor for the breaker

Answer

Higher ambient temperature on that side

Question 5

A commercial building experiences intermittent voltage sags. The utility feed tests normal. Where should the contractor investigate next?

Accepted Answer

Main distribution panel connections

Answer

Individual branch circuit loads

Answer

Building grounding electrode system

Answer

Emergency generator transfer switch

Question 6

What is the recommended maintenance interval for retorquing electrical connections in commercial switchgear per NFPA 70B?

Accepted Answer

Annually

Answer

Every 6 months

Answer

Every 3 years

Answer

Every 5 years