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National Electrical Code Articles and Information

Based on the 2017 NEC

by Mark Lamendola

National Electrical Code Top Ten Tips: Article 540, Motion Picture Projection Rooms

  1. While these rooms are becoming increasingly scarce, they still exist. If you want to operate a professional projector, you have to operate it in one of these permanently constructed rooms [540.10].
  2. A professional projector is one that uses 35 or 70mm film that has 5.4 perforations per inch. Or, it's one that uses carbon arc, xenon, or other light source that develops hazardous gases, dust, or radiation. Thus, the special room [540.2].

  3. Motor generator sets and transformers for the supply or control of current to the projection equipment must be in another room if nitrate film is used [540.11(A).
  4. If in the same room as the projection equipment, motor generator sets and transformers for the supply or control of current to the projection equipment must be of the enclosed, fan-cooled or enclosed peip-ventilated type [540.11(A)(1)] or comply with one of the other five requirements listed in 540.11.
  5. Overcurrent devices not normally required or used for projectors cannot be installed in projector rooms [540.11(B)]. This means you can't locate a branch circuit panel in that room.
  6. Any emergency systems associated with these rooms must comply with Article 700.
  7. You must provide a minimum of 30 inches of working space on each side of each motion picture projector [540.12]. Same for the rear.
  8. Supply conductors for outlets for arc and xenon projectors can't be smaller than 8AWG 540.14].
  9. Any cords used on portable equipment must be approved for hard usage [540.15].
  10. You can also use nonprofessional projectors in these rooms [540.31].


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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