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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 6

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. When you size the circuit conductors that run between the inverter output and the structure disconnect, base that on the output rating of the inverter [690.10(B)].
     
  2. Protect those conductors per Article 240, locating the overcurrent protection at the inverter [690.10(B)].
     
  3. Yes, you can use the inverter output of a standalone PV system to supply 120V to single-phase, 120/240V service equipment or distribution panels. But if you do this, there can't be any 240V outlets or any multiwire branch circuits.
     




  4. It is not a code violation to connect a standalone PV system without a battery bank or backup power system [690.10(D)]. If your power goes out, that's not going to cause the building to burn down. In fact, cutting the power is one of the first things the fire department will do. However, such a configuration is risky in other ways because it could leave you without power. For a family residence, such an arrangement is just a bad design.
     
  5. Don't backfeed circuit breakers that are marked "line" or "load" [690.10(E)].
     
  6. Arc fault circuit interruption appeared a few code cycles ago, and it was only a matter of time until it would make its way into Article 690. With the 2011 revision, it did [690.10(F)]. At first glance, the requirements seem more detailed than is necessary. But the power supply you're using is a bit more complicated. That's why the requirements include an annunciator and other provisions beyond what you normally have in an arc fault protection scheme.
     
  7. The disconnect must be able to disconnect all current-carrying conductors of the PV system from all other conductors in the structure [690.13]. Notice in this text that the NEC does not use the word "neutral," but instead says, "grounded conductor." You will find the relevant definitions in Article 100. Don't get them confused with each other; they are not automatically synonymous.
     
  8. As with a standard electric utility service, you're limited to 6 disconnects for the PV system [690.14(C)(4)].
     
  9. The grouping rule applies, also [690.14(C)(5)].
     
  10. Utility-interactive inverters don't have to be readily accessible. You can even mount them on the roof. But you must meet the requirements of [690.14(D)(1)-(4)].

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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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