E2 Overcurrent Protection Devices 2 — Questions and Answers
Question 1: NEC 230.95 requires ground-fault protection of equipment (GFPE) for solidly grounded wye services over 150V to ground, not exceeding 600V phase-to-phase, when the service disconnecting means is rated at or above:
- 400 amperes
- 600 amperes
- 800 amperes
- 1000 amperes (Correct answer)
Correct answer: 1000 amperes
NEC 230.95 requires GFPE for solidly grounded wye services exceeding 150V to ground but not more than 600V phase-to-phase when the service disconnecting means is rated 1000 amperes or more.
Question 2: Per NEC 240.83(D), circuit breakers used to switch 120-volt or 277-volt fluorescent lighting circuits must be listed and marked:
- HACR rated
- SWD or HID (Correct answer)
- Type AC only
- Current-limiting
Correct answer: SWD or HID
NEC 240.83(D) requires circuit breakers switching fluorescent lighting on 120V or 277V circuits to be listed and marked SWD (Switching Duty) or HID (High-Intensity Discharge).
Question 3: NEC 240.87 requires arc energy reduction measures for circuit breakers where the instantaneous trip setting is:
- 400 amperes or more
- 600 amperes or more
- 800 amperes or more
- 1200 amperes or more (Correct answer)
Correct answer: 1200 amperes or more
NEC 240.87 requires arc energy reduction methods for circuit breakers with instantaneous trip settings of 1200 amperes or more to reduce arc flash incident energy during maintenance activities.
Question 4: According to NEC 240.24(A), overcurrent devices shall not be located where they will be exposed to:
- Temperatures below 40°F
- Physical damage (Correct answer)
- Humidity above 60%
- Vibration from mechanical equipment
Correct answer: Physical damage
NEC 240.24(A) prohibits locating overcurrent devices where they are subject to physical damage, ensuring reliable operation when needed.
Question 5: Per NEC 240.24(D), overcurrent devices shall not be located in the vicinity of:
- Mechanical equipment rooms
- Non-combustible storage rooms
- Easily ignitable material (Correct answer)
- Damp locations if protected by weatherproof enclosures
Correct answer: Easily ignitable material
NEC 240.24(D) prohibits overcurrent devices from being located in the vicinity of easily ignitable material, such as in clothes closets, due to fire ignition risk from arcing.
Question 6: Per NEC 240.50(A), fuseholders for plug fuses shall not be used in circuits exceeding what voltage between conductors?
- 120 volts
- 125 volts (Correct answer)
- 150 volts
- 250 volts
Correct answer: 125 volts
NEC 240.50(A) limits plug fuse fuseholders to circuits not exceeding 125 volts between conductors.
Question 7: Under NEC 240.81, when a single-throw circuit breaker is used as a disconnecting means, the 'ON' position of the operating handle shall be in what direction?
- Downward
- To the right
- Upward (Correct answer)
- Any direction if clearly labeled
Correct answer: Upward
NEC 240.81 requires that for a single-throw circuit breaker, the 'ON' position of the operating handle shall be in the up direction.
E2 Overcurrent Protection Devices 2
NEC 230.95 requires ground-fault protection of equipment (GFPE) for solidly grounded wye services over 150V to ground, not exceeding 600V phase-to-phase, when the service disconnecting means is rated at or above: