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NEC Quiz: Article 404 Answers

by Mark Lamendola

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  1. All the switching must be done only in the ungrounded conductor [404.2].

  2. It's about where the grounded conductor for the controlled lighting circuit must be. Except for the seven applications listed, it must be at the location where the switches control the lighting loads that are supplied by a general-purpose branch circuit. An example exclusion is where the switch does not serve a habitable room or bathroom, and that really does cover a vast number of situations!

  3. The switch must be installed such that gravity will not tend to close it [404.6(A)]. That's why in the opening remarks you read about up for on and down for off. That said, there are switches approved for use in the inverted position. But they must have an integral mechanical means of ensuring the blades stay open when set open.

  4. You can't group or gang snap switches in enclosures with other snap switches, receptacle, or similar devices unless they are arranged so the voltage between adjacent devices does not exceed 300V [404.8(B)].
  5. A faceplate must completely cover the opening. Also, where the switch is flush-mounted, the faceplate must seat against the finished surface [404.9(A)]. DIY folks and even some electricians often muff this one. The problem is the box is not properly installed. If it sits back too far, they tighten down the plate mounting screw(s) so much they bend or even crack the plate. Or maybe they leave the switch mostly recessed back behind the cover. If the box sits out too far, they also overtigten in an attempt to force it toward the wall but typically must leave a gap anyhow.

    So when mounting a box, use the guide marks on the box to get it properly positioned in all dimensions. If the box is already mounted and the wall is already finished, you'll have to adjust the switch tangs and/or use special adapters that are sold for fixing bone-headed box installations that put the switch(es) in the wrong place in relation to the finished surface.

 

 

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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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