NEC Overcurrent Protection & Grounding 2 — Questions and Answers
Question 1: According to NEC 240.4(D), what is the maximum overcurrent protection permitted for 14 AWG copper conductors?
- 15 amperes (Correct answer)
- 20 amperes
- 25 amperes
- 30 amperes
Correct answer: 15 amperes
NEC 240.4(D) limits overcurrent protection for 14 AWG copper to 15 amperes regardless of the conductor's ampacity.
Question 2: What NEC article governs the use of ground-fault circuit-interrupter (GFCI) protection?
- Article 210 (Correct answer)
- Article 230
- Article 250
- Article 310
Correct answer: Article 210
Article 210 covers branch circuits, including the GFCI protection requirements for receptacles in wet and damp locations.
Question 3: What is the minimum size copper equipment grounding conductor (EGC) required for a circuit protected by a 60-ampere overcurrent device per NEC Table 250.122?
- 10 AWG (Correct answer)
- 8 AWG
- 6 AWG
- 4 AWG
Correct answer: 10 AWG
NEC Table 250.122 requires a minimum 10 AWG copper EGC for circuits protected at 60 amperes.
Question 4: Under NEC 250.24(A), a service-entrance grounded conductor (neutral) must be connected to the grounding electrode system at which location?
- At the service disconnecting means enclosure (Correct answer)
- At the first panelboard downstream
- At the meter base only
- At the transformer secondary
Correct answer: At the service disconnecting means enclosure
NEC 250.24(A) requires the grounded conductor to be bonded to the grounding electrode system at the service disconnecting means.
Question 5: A 20-ampere, 120-volt branch circuit breaker trips repeatedly under normal load. Per NEC principles, what is the FIRST corrective action?
- Evaluate the actual load versus the circuit's rated capacity (Correct answer)
- Replace the breaker with a 30-ampere device
- Install a larger wire on the circuit
- Add a second circuit breaker in parallel
Correct answer: Evaluate the actual load versus the circuit's rated capacity
NEC requires conductors and overcurrent devices to be properly sized for the load; the load must be evaluated before upsizing protection.
Question 6: What does NEC 250.119 require regarding identification of equipment grounding conductors?
- Continuous green color or green with yellow stripes, or bare (Correct answer)
- White or gray insulation only
- Orange insulation for high-voltage circuits
- Black insulation with green tape at terminations
Correct answer: Continuous green color or green with yellow stripes, or bare
NEC 250.119 requires EGCs to be identified by green insulation, green with yellow stripe, or bare copper.
Question 7: Per NEC 240.21(B)(1), a tap conductor from a feeder must not exceed what length when not otherwise protected at its point of supply?
- 10 feet (Correct answer)
- 25 feet
- 50 feet
- 100 feet
Correct answer: 10 feet
NEC 240.21(B)(1) allows tap conductors up to 10 feet without overcurrent protection at the tap point if specific conditions are met.
NEC Overcurrent Protection & Grounding 2
According to NEC 240.4(D), what is the maximum overcurrent protection permitted for 14 AWG copper conductors?