Overcurrent Protection Flashcards
7 cards from real IEC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Overcurrent Protection flashcards as text
What is the maximum standard ampere rating for a fuse per NEC 240.6(A)?
Answer: 600A
NEC 240.6(A) lists 600A as a standard ampere rating for overcurrent protective devices.
Which type of fuse is designed to open on sustained overloads but NOT on normal motor starting currents?
Answer: Time-delay fuse
Time-delay (dual-element) fuses tolerate short-duration inrush currents while still protecting against sustained overloads.
Per NEC 240.4(D), a 14 AWG copper conductor used for general-purpose branch circuits must be protected at no more than:
Answer: 15A
NEC 240.4(D) limits overcurrent protection for 14 AWG copper conductors to 15A.
A fusible disconnect that opens all ungrounded conductors simultaneously is described as which type of fuse?
Answer: Multi-pole
Multi-pole (multi-element) fuses interrupt all ungrounded conductors at once, preventing single-phasing on three-phase equipment.
Where must an overcurrent device NOT be located per NEC 240.24(E)?
Answer: In bathrooms of dwellings
NEC 240.24(E) prohibits overcurrent devices in bathrooms of dwelling units, dormitories, and guest rooms.
The NEC term for a protective device that limits the peak let-through current during a fault is:
Answer: Current-limiting fuse
Current-limiting fuses open fast enough to limit the peak let-through current and reduce fault energy on the system.
Per NEC 240.21, a tap conductor may be up to 25 feet long without overcurrent protection at the tap point provided it meets which condition?
Answer: It is enclosed in a raceway and terminates in a single OCPD
The 25-foot tap rule requires the tap conductors to be in a raceway and terminate in a single overcurrent protective device.