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Overcurrent Protection & Grounding Flashcards

7 cards from real NEC 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 & Grounding flashcards as text

  1. Per NEC 240.87, what protection is required for circuit breakers rated 1200 amperes or more?

    Answer: Arc energy reduction means

    NEC 240.87 requires arc energy reduction (e.g., zone-selective interlocking, differential relaying, or maintenance mode) for breakers rated 1200A or more.

  2. What does NEC 250.4(A)(5) require regarding effective ground-fault current paths?

    Answer: The path must have sufficiently low impedance to allow overcurrent devices to operate

    NEC 250.4(A)(5) requires the fault current path to have low enough impedance to facilitate operation of the overcurrent protective device.

  3. Which conductor is used to bond metal water piping to the electrical grounding system per NEC 250.104(A)?

    Answer: A main bonding jumper sized per Table 250.102(C)(1)

    NEC 250.104(A) requires the interior metal water piping bonding conductor to be sized per Table 250.102(C)(1) based on the service conductor size.

  4. What is the minimum standard size for a main bonding jumper conductor connecting the neutral bar to the equipment grounding bar in a 200-ampere residential service panel per NEC 250.28(D)?

    Answer: 4 AWG copper

    For a 200A service with 2/0 AWG service conductors, Table 250.102(C)(1) yields a 4 AWG copper main bonding jumper minimum.

  5. NEC 240.60 applies to cartridge fuses and fuseholders. What does it prohibit?

    Answer: Installing a fuse of higher amperage in a fuseholder rated for a lower amperage

    NEC 240.60 requires fuseholders to be designed so that a fuse of a higher rating than intended cannot be installed.

  6. Under NEC 250.53(A)(2), when a single ground rod does not achieve 25 ohms or less resistance to ground, what is required?

    Answer: One additional electrode must be installed

    NEC 250.53(A)(2) requires one supplemental electrode when a single rod electrode exceeds 25 ohms resistance to earth.

  7. Per NEC 240.4(C), which conductors are not permitted to have their overcurrent protection increased to the next standard size above their ampacity?

    Answer: Fixture wires and flexible cords

    NEC 240.4(C) prohibits applying the next-standard-size-up rule to fixture wires and flexible cords, which must be protected per their specific ampacity.