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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 2

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. You can install a PV system to supply a structure, even if other systems also supply it [690.4(A)].
  2. To put circuits of PV systems in the same raceway as circuits of a non-PV system, separate the circuits with a partition [690.4(B)]. Identify and group the PV conductors, making sure you identify them at all points of termination not just the system end points.
  3. Arrange all modules and panels such that removing one doesn't interrupt a grounded conductor to another PV source circuit  [690.4(C)].
  4. Any inverters, motor generators, PV modules, PV panels, or charge controllers you use in your PV system must be identified for, and listed for, the application  [690.4(D)].
  5. Only qualified persons can install and wire the PV system electrical components  [690.4(E)]. Keep in mind that the NEC uses the OSHA definition of "qualified" and it has a specific legal meaning. See Article 100 for this definition. In the case of PV systems, the most pertinent part is the installer "has received safety training to recognize and avoid the hazards involved." That means training specific to this type of installation.

    Such training may be provided by the manufacturer or a manufacturer-approved party. A firm that regularly installs PV systems and has a training program in place can most likely be the source of such training for new installers under its supervision.

  6. Route PV circuits along building structural members, wherever you can visually determine where those members are. The NEC says "by observation," and that's all you're technically required to do  [690.4(F)]. But it's not much of a stretch from there to using building drawings, stud finders, measurements, and other means to locate these members. You want the conductors to be as secure in their mounting as is reasonably possible.
  7. If you end up routing PV circuits in built-up, laminate, or membrane roofing materials, make sure you clearly mark the location of these circuits [690.4(F)].
  8. If you install a bipolar PV system, calculate the sum of the two monopole subarrays. If it exceeds the rating of the conductors and connected equipment, physically separate the two subarrays. Install the wiring in separate raceway all the way to the inverter  [690.4(G)].
  9. A PV system can have multiple utility-interactive inverters in a single structure. If they are remote from each other, list them all in a directory and install the directory at each dc PV system disconnecting means and at the main service disconnecting means  [690.4(H)]. The idea here is to give First Responders full information on how to shut down power inside the building so they don't get electrocuted trying to fight a fire there.
  10. If you have multiple inverters but they are all grouped the inverters at the service, a directory isn't required. The logic behind waiving this requirement is the same logic for mandating the directory when these inverters aren't grouped in one location. Generally, you want to make it safer and easier for firefighters whenever possible. So the default should be to group the disconnects at the service unless there's a compelling reason to do otherwise.

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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