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National Electrical Code Articles and Information

NEC Quiz: Article 406, Part 2 Answers

by Mark Lamendola

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  1. In the general installation requirements, we find 406.4(C) Methods of Grounding. So at first blush, it appears you ground a receptacle. But read more closely. You're connecting it to the equipment grounding conductor (EGC). The EGC is actually a bonding jumper that has, by long tradition, been misnamed a "grounding" conductor. Refer to the Article 100 definitions of grounding and bonding. This confusing misuse of the word "grounding" occurs elsewhere in this Section. At some point in a future revision of the NEC, this will be cleared up. Over the past few Code cycles, the NEC has made huge progress on this issue. Clearly, more progress is yet to be made.

  2. First of all, non-grounding type receptacles don't solve noise problems. It's debatable whether isolated ground receptacles do either, though those are often recommended for such problems. Sometimes, a grounding-type receptacle is used in an old home with a two-wire system. There's no EGC in the cabling, so unless you can run that EGC you don't install a grounding-type receptacle. I've pulled such receptacles out and put the old style back in, because using them without an actual EGC connection can cause safety problems.

    The answer depends upon whether there is an EGC. If an EGC, use a grounding type receptacle. The NEC has a really good solution, for when there is no EGC. Use a GFIC that is marked "No Equipment Ground." See all the rules on this issue in 406.4(D)(1) and (2).

  3. The receptacle must be installed such that the yoke (or strap) is held rigidly at the finished surface [406.5(A)].

  4. The receptacle must be installed such that the yoke (or strap) is held rigidly against the box or box cover [406.5(B)].
  5. The receptacle must be installed such that the yoke (or strap) is held against the cover by more than one screw [406.5(C)]. Alternatively, you can use a device assembly or box cover listed and identified for securing by a single screw.



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How the NEC is arranged

  1. The first four Chapters of the NEC apply to all installations.
  2. Article 90 precedes Chapter One, and establishes the authority of the NEC.
  3. Article 80 follows the body of the NEC; it exists as Annex H. It provides the requirements for administration.
  4. Chapters 5, 6, and 7 are the "special" chapters, covering special: occupancies, equipment, and conditions (in that order).
  5. Chapter 8 provides the requirements for communications systems.
  6. Chapter 9 provides tables.
  7. The appendices provide mostly reference information.
  8. Appendix D contains examples that every NEC user should study.

Try your NEC moxy:

  • Do you know the difference between bonding and grounding? Hint: Look in the NEC, Article 100.
  • Does the NEC refer to grounding incorrectly in any of its articles? Yes! So be careful to apply the Article 100 definitions. Don't ground where you should bond.
  • When doing motor load calculations, which Article covers hermetic motors? Answer: While Article 440 covers the application of hermetic motors, it does so only by amending Article 430 because hermetic motors are a special case of motors. For motor load calculations, refer to Article 430.
  • Does the NEC provide a voltage drop requirement? Yes! It does so in a special case, which is Article 648 Sensitive Electronic Equipment. But for general applications, it does not provide a requirement; it merely provides a recommendation in a couple of FPNs.
  • Take our Code Quizzes.

Remember other applicable codes, rules, standards, and references:

  • OSHA's electrical worker safety rules.
  • IEEE standards.
  • NETA standards.
  • NFPA standards.
  • International Codes (if applicable to the installation).
  • State Codes (if the state has them).
  • Local ordinances and permit requirements.
  • Local fire codes.
  • Manufacturer requirements or guidelines.
  • Customer security requirements.
  • Industry standards.
  • Your company's own internal standards, practices, and procedures.
  • Engineering drawing notes.



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