Ecmweb 8328 7 21 16wwhlarge
Ecmweb 8328 7 21 16wwhlarge
Ecmweb 8328 7 21 16wwhlarge
Ecmweb 8328 7 21 16wwhlarge
Ecmweb 8328 7 21 16wwhlarge

What’s Wrong Here? Hint: Near Screw Up (or Down in this Case)

July 21, 2016
NEC rules on screw spacing near cables, raceways, and boxes

How well do you know the Code? Think you can spot violations the original installer either ignored or couldn't identify? Here's your chance to moonlight as an electrical inspector and second-guess someone else's work from the safety of your living room or office. It's your turn to identify the violation.

Hint: Near screw up (or down in this case)

Find the Answer

Whew! That was a close call for the conductors in this EMT. It was also a close call for the roofer sinking this screw into the metal decking! The workers who were making repairs to the roof almost sank a self-tapping sheet metal screw right through the pipe. This would have damaged the pipe and the wires inside the pipe, and could have even injured the roofer who was making the repairs.

This is exactly why Sec. 300.4(E) requires cables, raceways, and boxes to be installed so that there is a spacing of at least 1½ in. between the lowest portion of the metal-corrugated sheet roof decking material and the boxes, raceways, or cables. The Exception to 300.4(E) permits RMC and IMC to be installed without the 1½-inch spacing, since the wall thickness of these raceways is better able to protect the wiring inside them. Section 358.12(1) prohibits EMT from being used where it would be exposed to severe physical damage during or after installation. I would say that a self-tapping screw penetrating the EMT would constitute as severe physical damage.

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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