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National Electrical Code Articles and Information

Based on the 2008 NEC

by Mark Lamendola

National Electrical Code Top Ten Tips: Article 520 -- Theaters and Similar Locations

  1. Article 520 applies to all structures or parts of structures used for presentations and/or performances. Basically, if it has a stage, auditorium, or audience seating area, it's covered by Article 520.
     
  2. If you use nonmetallic raceway, it must be encased in at least 2 in. of concrete [520.5(A)], unless it's for Article 640 circuits.
     
  3. Article 520 puts a twist on raceway fill. If using a raceway other than an auxiliary gutter (or aux raceway), the normal raceway fill requirements of Table 1, Chapter 9 apply. Otherwise, the sum of the cross-sectional area of all contained conductors at any cross section can't exceed 20% of the interior cross-section of the gutter (but the 30-conductor limit of 366.22 and 376.22 does not apply) [520.6].
     
  4. Any branch circuit that supplies receptacles can supply stage set lighting [520.9].
     
  5. Portable equipment used outdoors must be supervised by qualified personnel and barriered from access to the public [520.10].
     
  6. Stage switchboards must be of the dead-front type [520.21].
     
  7. Stage switchboard feeders can be one of the only three types described in 520.7(A).
     
  8. Footlights, border lights, and proscenium lights are limited to circuits of 20A or less [520.41(A)].
     
  9. A road show connection panel is a type of patch panel, and it must comply with 520.50(A) through (D).
     
  10. There are many types of portable stage equipment other than portable switchboards (arc lamps, PDUs, busbars, receptacles, etc.), and these are covered in Part V of Article 520. Requirements address such issues as festoons, conductor types, conductor ampacity, and adapters.

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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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