Code Q&A

Nov. 3, 2011
Q. What are the acceptable wiring methods for photovoltaic (PV) circuits inside buildings/structures?

Q. What are the acceptable wiring methods for photovoltaic (PV) circuits inside buildings/structures?

A. PV system DC conductors (source and output) run inside a building/structure must be contained in a metal raceway, Type MC cable, or metal enclosure [690.31(E)]. Wiring methods cannot be located within 10 in. of the roof decking or sheathing, except where located directly below the roof surface that's covered by PV modules and associated equipment and must be run perpendicular (90°) to the roof penetration point [690.31(E)(1)]. Note: The 10 in. from the roof decking/sheathing requirement is to prevent accidental contact with energized conductors from saws used by firefighters for roof ventilation during a structure fire.

FMC smaller than trade size ¾ in. or Type MC cable smaller than 1 in. in diameter installed across ceilings or floor joists must be protected by substantial guard strips that are at least as high as the wiring method. Where run exposed, other than within 6 ft of their connection to equipment, wiring methods must closely follow the building surface or be protected from physical damage by an approved means [690.31(E)(2)].

Wiring methods and enclosures containing PV source conductors must be marked with the wording "Photovoltaic Power Source" by labels or other approved permanent marking means [690.31(E)(3)]. The marking required by 690.31(E)(3) must be visible after installation and appear on every section of the wiring system separated by enclosures, walls, partitions, ceiling, or floors. Spacing between labels/marking must not be more than 10 ft, and labels must be suitable for the environment [690.31(E)(4)].

About the Author

Mike Holt

Mike Holt is the owner of Mike Holt Enterprises (www.MikeHolt.com), one of the largest electrical publishers in the United States. He earned a master's degree in the Business Administration Program (MBA) from the University of Miami. He earned his reputation as a National Electrical Code (NEC) expert by working his way up through the electrical trade. Formally a construction editor for two different trade publications, Mike started his career as an apprentice electrician and eventually became a master electrician, an electrical inspector, a contractor, and an educator. Mike has taught more than 1,000 classes on 30 different electrical-related subjects — ranging from alarm installations to exam preparation and voltage drop calculations. He continues to produce seminars, videos, books, and online training for the trade as well as contribute monthly Code content to EC&M magazine.

Voice your opinion!

To join the conversation, and become an exclusive member of EC&M, create an account today!

Sponsored Recommendations

Electrical Conduit Comparison Chart

CHAMPION FIBERGLASS electrical conduit is a lightweight, durable option that provides lasting savings when compared to other materials. Compare electrical conduit types including...

Don't Let Burn-Through Threaten Another Data Center or Utility Project

Get the No Burn-Through Elbow eGuide to learn many reasons why Champion Fiberglass elbows will enhance your data center and utility projects today.

Considerations for Direct Burial Conduit

Installation type plays a key role in the type of conduit selected for electrical systems in industrial construction projects. Above ground, below ground, direct buried, encased...

How to Calculate Labor Costs

Most important to accurately estimating labor costs is knowing the approximate hours required for project completion. Learn how to calculate electrical labor cost.