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National Electrical Code Articles and Information

Based on the 2020 NEC

by Mark Lamendola

National Electrical Code Top Ten Tips: Article 551, Recreational Vehicles and Recreational Vehicle Parks. Part 1.

  1. Article 551 defines "recreational vehicle" as a vehicle-type unit used as temporary living quarters for recreational, camping, or travel use. The four basic entities are travel trailer, camping trailer, truck camper, and motor home [551.2].
  2. An RV not used for the purposes stated in 551.2 doesn't need to comply with the requirements for the number or capacity of circuits. It must, however, comply with all of the other requirements if it has a power source that is 120V, 120/208V, or 120/240V [551.4].
  3. You must bond the voltage converter enclosures with a minimum 8AWG copper conductor [551.20(C)].
  4. You cannot use autotransformers with RVs [551.20(E)].
  5. Part III provides the requirements for providing power to an RV from sources other than 120V, 120/208V, or 120/240V systems [551.30 - 33]. Typically, this means a generator.
  6. If you use a generator, it must be bonded to the RV chassis [551.30(A)]. This bonding requirement actually applies to all power sources. The point of it is to prevent a difference of potential.
  7. For 120V, 120/208V, or 120/240V systems, you must provide GFCI [551.40].
  8. Each RV must contain one of the three branch circuit arrangements detailed in 551.42(A) though (D).
  9. The working clearance for the panelboard must be at least 24 inches wide and 30 inches deep [551.45(B)]. This limits where you can place the panelboard. In addition to structural considerations, factor in storage. You don't want to locate the panel where someone is likely to store combustibles or other materials.
  10. The point of entrance of a power supply assembly must meet specific requirements, which are detailed in 551.46(E). These include, for example, that it must be within 15 feet of the rear and to the left of the longitudinal center of the vehicle.


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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