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National Electrical Code Articles and Information

Based on the 2011 NEC

by Mark Lamendola

National Electrical Code Tips: Article 690 -- Solar Photovoltaic Systems, Part 3

Only about 15% to 20% of the work of installing a Solar Photovoltaic (PV) System is electrical. But that electrical portion can easily result in disaster if not done correctly. Thus, Article 690 provides requirements for that portion.

  1. All grounded dc PV arrays must have dc ground fault protection [690.5].
     
  2. There are two exceptions to the preceding rule [690.5, Exc].
     
  3. The GFCI must detect ground-fault current, interrupt the flow of ground-fault current, and provide an indication of the fault [690.5(A)]. The GFCI can open the grounded conductor of the circuit as a means of interrupting the flow. Note, this does not mean the grounding conductor. And if it does employ this method, it must open all conductors of the circuit [690.5(A)].
     




  4. One way a faulted circuit can be isolated is by opening the ungrounded conductors [690.5(B)].
     
  5. Another way a faulted circuit can be isolated is by having the inverter or charge controller stop supplying power to the output circuits [690.5(B)].
     
  6. Article 690 requirements for PV source circuits don't apply to ac modules. Why is this? Because the NEC considers their source circuits to be internal wiring [690.6(A)].
     
  7. You must treat the output of an ac module as if it's an inverter output circuit [690.6(B)].
     
  8. You can use a single disconnect for the combined ac output of multiple ac modules, but each must also have its own disconnect [690.6(C)].
     
  9. You can use a single GFCI for ac module systems [690.6(D)].
     
  10. For the output circuits of ac modules, you can size the conductors and overcurrent protection devices per 240.5(B)(2).
     

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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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