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National Electrical Code Articles and Information

NEC Quiz: Article 240 Answers

by Mark Lamendola

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  1. [240.4(A)]. This is a trick question. Actually, you don't install OCPDs on a fire pump (see Article 695). OCPDs aren't required where interruption of the circuit would cause a hazard.
     

  2. [240.4(G)]. Yes. See Table 240.4(G).
     

  3. [240.12]. They are coordinated short-circuit protection and overload indication based on monitoring systems or monitoring devices.
     

  4. [240.30(A)(1)]. Install them in enclosures, cabinets, cutout boxes, or equipment assemblies; or
    Mount them on open-type switchboards, panelboards, or control boards that are in rooms free from dampness (and from easily ignitable material) and are accessible only to qualified personnel.
     

  5. [240.93(C)]. You can't use it if:
    1. Motors are connected on the load side of the higher-rated OCPD and on the line side of the lower-rated OCPD, and
    2. The sum of the motor full-load currents exceeds 1 percent of the interrupting rating of the lower-rated OCPD.

 

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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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