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Grounding and Bonding 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.

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  1. Under NEC 250.50, when multiple grounding electrodes are present at a structure, what must be done?

    Answer: They must all be bonded together to form a grounding electrode system

    NEC 250.50 requires all grounding electrodes present at a structure to be bonded together into a single grounding electrode system.

  2. Per NEC 250.118, which of the following is NOT listed as an acceptable equipment grounding conductor type?

    Answer: A bare aluminum conductor run underground in direct contact with the earth

    Bare aluminum conductors are not permitted as EGCs underground in direct earth contact due to corrosion; NEC 250.118 does not list this as an acceptable EGC.

  3. What does NEC 250.148 require regarding equipment grounding conductors in junction boxes?

    Answer: All EGCs must be connected together and to the box if it is metal

    NEC 250.148 requires all EGCs entering a box to be connected together and, if the box is metal, to the box itself.

  4. What is a 'concrete-encased electrode' (Ufer ground) per NEC 250.52(A)(3)?

    Answer: At least 20 feet of #4 AWG or larger steel rebar or wire encased in concrete in contact with earth

    NEC 250.52(A)(3) defines a concrete-encased electrode as at least 20 feet of 1/2-inch rebar or 4 AWG wire encased in at least 2 inches of concrete in contact with the earth.

  5. Per NEC 250.97, where high-voltage (over 250V to ground) service conduit connections are made to enclosures, what is required?

    Answer: Bonding jumpers around reducing washers and concentric or eccentric knockouts

    NEC 250.97 requires bonding jumpers to be used around reducing washers or impaired knockouts at over 250V services to ensure a reliable bond.

  6. Under NEC 250.36, what type of grounding is used for a high-impedance grounded neutral system?

    Answer: The neutral is connected to ground through an impedance device to limit fault current

    NEC 250.36 covers high-impedance grounded neutral systems where an impedance device connects the neutral to ground, limiting ground fault current.

  7. According to NEC 250.4(A)(5), what is the primary purpose of equipment bonding?

    Answer: To establish a low-impedance path to facilitate overcurrent device operation during ground faults

    NEC 250.4(A)(5) states that bonding must provide a low-impedance path that enables the overcurrent device to operate and clear ground faults quickly.