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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 511 -- Commercial Garages, Repair and Storage

  1. The occupancies covered by Article 511 include locations used for the service and repair of self-propelled vehicles (such as cars and buses) that use flammable liquids or gases for fuel or for power [511.1].
  2. Article 511 distinguishes between major repair garages and minor repair garages [511.2]. The requirements that follow differ, depending on which of these is the location of the installation.
  3. If you store, handle, or transfer Class I fuels in a given area, you must install electrical equipment per Class I requirements [511.3].
  4. Parking garages can be unclassified [511.3(A)], as long as they don't double as some other area that is classified (e.g., fuel dispensing).
  5. Floors, pits, and depression are critical areas, because liquids and heavier-than-air gases can pool in low areas.
  6. Ceilings and any "inverted depressions" (e.g., spaces between joists) in them are critical areas, because lighter than air gases can accumulate in them.
  7. Areas adjacent to classified areas can be unclassified, if flammable vapors are unlikely to be released and certain other conditions are met [511.3(E)(1)].
  8. If a garage location is Class I per 511.3, wire it per Article 501 [511.4(A)].
  9. If a garage location is Class I per 511.3, install only equipment that conforms to Article 501 [511.4(B)].
  10. Installations above Class I locations must also meet certain requirements [511.7], so don't think only of equipment in those locations.

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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