What's Wrong Here?

What’s Wrong Here? Hint: The Sky is Falling!

May 22, 2019

Think you know how this installation violates the NEC?

Ecmweb Com Sites Ecmweb com Files 5 23 19wwhweb

Hint: The sky is falling!

See the answer below.

Chicken Little would be upset if he looked up and saw the wiring below this metal corrugated roof. While the sky might not be falling, this electrical installation is failing. Installing raceways and cables this close to the roofing surface, where long screws are clearly visible and penetrating the roof, is putting the wiring methods in harm’s way.

Section 300.4(E) requires raceways, cables or boxes installed in locations underneath metal-corrugated sheet roof decking to be installed with at least 1½ in. of space from the lowest surface of the roof decking to the top of the raceways, cables or boxes. This reduces the likelihood of the wiring being damaged from the long screws, which tend to be used during roofing repairs. As you may notice in the photo, there are many screws penetrating down through the metal roof decking due to previous repairs made to the roof.

Section 410.10(F) requires the same 1½ in. spacing for luminaires installed in these locations.

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.