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National Electrical Code Articles and Information

Based on the 2011 NEC

by Mark Lamendola

National Electrical Code Top Ten Tips: Article 551, Recreational Vehicles and Recreational Vehicle Parks. Part 2.

  1. Article 551 amends the Chapter wiring methods; it does not replace them. Where Article 551 is silent, Chapter 3 requirements apply. [551.47(A)].
     
  2. You can't mix metallic and nonmetallic wiring methods. That is, use nonmetallic raceway (or non-metallic sheathed cable) if you use nonmetallic boxes. [551.47(C)].
     
  3. In these wiring systems, no bend can have a radius of less than five wire diameters [551.47(H)].
     
  4. Any prewiring must meet the applicable part of 551.47(Q), (R), or (S).
     
  5. Any luminaire installed over a bathtub or in a shower stall must be GFCI-protected [551.53(B)].
     
  6. Do not ground interior electrical equipment. Where 551.55 speaks of "grounding," it means "bonding." If you review these terms in Article 100, you will see the terminology error when you read the requirements. Make sure you bond, not ground, interior equipment.
     
  7. Bonding conductors for non-current carrying metal parts must be at least #8AWG [551.56(C)].
     
  8. You will find the requirements for RV Parks in Article 551, Part VI. Calculate loads per 551.73.
     
  9. You'll find another terminology error in 551.75. It should say, "...shall be grounded and bonded..." but omits the bonded part.
     
  10. This grounding/bonding error is repeated in 55.76. You will have to refer back to the Article 100 definitions to make sense of these requirements. You must comply with the intent of the NEC here, not with what it says. If you ground where you should bond, someone can be electrocuted due to that error.

 

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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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