what's wrong here

What’s Wrong Here? Hint: Too Close for Comfort

Feb. 7, 2024
Think you know how this installation violates the NEC?

Hint: Too close for comfort

If you look closely, you can see a Rigid PVC conduit installed right up against the metal-corrugated sheet roof decking and next to a couple of screws that have penetrated the metal roof decking. Installing Rigid PVC conduit this close to the metal roof decking is a violation of Sec. 300.4(E) which requires raceways, cables, and boxes to be installed with at least 1 ½ inches of space between the lowest surface of the roof decking, to the top of the raceway, cable, or box. Those screws that have penetrated the roof next to the Rigid PVC conduit are the exact reason why this 1 ½ in. spacing is required.

In this case, no wiring was damaged by those screws, but I have seen and published pictures of many other installations where roofing repairs were made, and wiring was damaged by the screws used by the contractors who were making the repairs to the roof. Section 300.4(E) Ex. 1 informs us that RMC and IMC are not required to have the 1 ½ in. spacing. Exception 2 was added to eliminate the 1 ½ in. spacing requirement where the metal roof decking is covered with a concrete slab at least 2 inches thick.

About the Author

Russ LeBlanc | Owner

Russ started in the electrical trade as an apprentice in 1985. He worked his way up to become a Journeyman Electrician and then eventually became a Master Electrician and Licensed Construction Supervisor. In 1999 Russ become an Electrical Instructor for The Peterson School of Engineering in Massachusetts where he developed his passion for teaching, and quickly became Department Head of Electrical Instruction. Russ has taught thousands of apprentices, electricians, engineers, inspectors, and other electrical professionals during his career as an instructor. He continues to provide electrical professionals with Electrical Code seminars, Arc-Flash Awareness training seminars and educational material through his LeBlanc Consulting Services in North Reading, MA whose specialty is educating electricians. He has been an active member of the NFPA Electrical Section and has authored hundreds of National Electrical Code proposals and comments which have become Code rules to improve the safety for the electrical industry. Russ is also an IAEI certified Electrical Inspector.

Please visit www.russleblanc.net for more information.

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