Choose the best answer:

  1. The size of the grounding electrode conductor for a building or structure supplied by a feeder cannot be smaller than that identified in _____, based on the largest ungrounded supply conductor.
    a) Sec. 250.66
    b) Sec. 250.122
    c) Table 250.66
    d) Sec. 250.56

  2. In general, equipment bonding jumpers may not be longer than 6 ft, but they can be longer than 6 ft at outside pole locations for the purpose of bonding or grounding isolated sections of metal raceways or elbows installed in exposed risers of metal conduit or raceway.
    a) True
    b) False

  3. A metal water piping system must be bonded to _____.
    a) the service equipment enclosure
    b) the grounded (neutral) conductor at the service
    c) the grounding electrode conductor where of sufficient size
    d) Any of these

  4. Where exposed structural steel is interconnected to form a steel building frame, is not intentionally grounded, and may become energized, it must be grounded to _____.
    a) the service equipment enclosure
    b) the grounded (neutral) conductor at the service
    c) the grounding electrode conductor where of sufficient size
    d) Any of these

  5. A receptacle's grounding terminal doesn't need a separate bonding jumper if the receptacle is installed in a box flush with the surface and there is direct metal-to-metal contact between the device yoke and the box.
    a) True
    b) False

  6. Where circuit conductors are _____ within a box, equipment grounding conductors associated with those circuit conductors must be spliced or joined within or to the box with devices suitable for the use.
    a) spliced
    b) terminated on equipment
    c) a or b
    d) none of these



Answers and Discussion

  1. a, Sec. 250.66. The size of the grounding electrode conductor for a building or structure supplied by a feeder cannot be smaller than that identified in 250.66 based on the largest ungrounded supply conductor. In the 1999 NEC, this conductor to the grounding electrode was called a “grounding conductor,“ and it was sized for equipment grounding in accordance with Table 250-12.

  2. a, True. Per 250.102(E), service lateral conductors and raceways not owned by the utility company at the time of installation are subject to the rules of the NEC. The serving utility often mandates that a metal elbow and/or metal raceway be installed at the pole. Many times these metal parts are not bonded to an effective fault current path. This new rule in the 2002 Code provides a method for the electrician to bond the isolated parts to the grounded (neutral) conductor at the pole. The bonding jumper is sized according to 250.102(C), which specifies that you use Table 250.66. Note: Metal service elbows need not be bonded or grounded if they have 18 in. or more of cover (250.80 Ex).

  3. d, Any of these. Deletion of the word “interior” from 250.104(A)(1) made it necessary to bond to the electrical supply source all metal water piping systems in or “attached to the exterior” of a building or structure.

  4. d, Any of these. New language in 250.104(C) requires all structural steel — whether interior or exterior — to be bonded where it is likely to become energized. The 1999 NEC required interior, but not exterior, structural steel systems to be bonded. Also, this bonding jumper must be sized according to Table 250.66, instead of Table 250.122.

  5. b, False. Following changes to 250.146, boxes mounted “at the surface” are no longer acceptable for grounding receptacles.

  6. c, a or b. Revised text in 250.148 clarifies that equipment grounding conductors are only required to terminate to the metal box if the circuit conductors terminate to equipment within the box or if the circuit conductors are spliced within the box. For example, equipment grounding conductors pulled through a metal junction box need not be spliced together, nor are they required to terminate to the metal enclosure.

Questions and answers excerpted from Mike Holt's Illustrated Changes to the NEC, 2002 Edition.

Are you still confused by the Code? For additional information on Code-related topics please visit www.mikeholt.com or send an e-mail directly to the author at mike@mikeholt.com.