Journeyman Electrician's Overcurrent Protection Flashcards
7 cards from real Journeyman Electrician’s Exam practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Journeyman Electrician's Overcurrent Protection flashcards as text
A dual-element time-delay fuse is particularly useful for protecting circuits with:
Answer: Motor loads with high inrush currents
Dual-element time-delay fuses tolerate the high inrush current of motor starting while still protecting against sustained overloads.
Under NEC 230.91, where must the service overcurrent protective device be installed?
Answer: At the first accessible point after the service entrance conductors enter the building
NEC 230.91 requires the service OCPD to be an integral part of the service disconnecting means located at the first accessible point of entry.
What maximum number of overcurrent devices may serve as the service disconnecting means for a single building under NEC 230.71?
Answer: Six
NEC 230.71(A) limits the service disconnecting means to a maximum of six switches or circuit breakers for a single service.
A 40-ampere, 240-volt branch circuit feeds an electric range. The range's nameplate rating is 8.75 kW. Is this circuit properly protected?
Answer: Yes, 40 amperes satisfies the demand calculation
NEC 220.55 and Table 220.55 allow demand factors; a 40A circuit is the minimum required for an 8.75 kW range and is acceptable.
Current-limiting fuses reduce the let-through energy during a fault primarily by:
Answer: Clearing the fault in less than one-half cycle
Current-limiting fuses clear high-magnitude faults in less than a half cycle (0.00833 s), drastically reducing let-through I²t energy.
When a circuit breaker is used in a location that is inaccessible except by portable means (e.g., ladders), it:
Answer: Is still permitted as an OCPD but not as the sole disconnect
NEC 240.24(A) requires OCPDs to be readily accessible; a breaker that requires a ladder is not readily accessible and cannot serve as the disconnect.
An OCPD for a storage battery system must be installed within how many inches of the battery terminals per NEC 480.5?
Answer: 12 inches
NEC 480.5 requires the OCPD for battery systems to be installed within 12 inches of the battery terminals to protect the short unprotected conductor.