Ecmweb 18374 Nec Illustrated Catastrophes 0318 Pr 2
Ecmweb 18374 Nec Illustrated Catastrophes 0318 Pr 2
Ecmweb 18374 Nec Illustrated Catastrophes 0318 Pr 2
Ecmweb 18374 Nec Illustrated Catastrophes 0318 Pr 2
Ecmweb 18374 Nec Illustrated Catastrophes 0318 Pr 2

Illustrated Catastrophes: A Rainbow of Right and Wrong

March 17, 2018
More Code catastrophes uncovered and corrected in these faulty installations

All references are based on the 2017 edition of the NEC.

A Rainbow of Right and Wrong

This photo shows us the full spectrum of rights and wrongs. On the far left is an installation of running boards attached to the underside of the joists with NM cables securely fastened to them. This method of installing NM cables is found at the “meets Code requirements” end of the spectrum. The white NM cables stapled directly to the bottom of the joists are found at the “does not meet Code requirements” end of the spectrum. Section 334.15(C) requires NM cables smaller than two 6 AWG or three 8 AWG to be run either through holes bored through the joists or installed on running boards like the installation on the left side of the photo.

For interior branch circuits or feeder installations of SE cables, Sec. 338.10(B)(4)(a) requires installers to follow the rules in Art. 334. The larger-sized gray SER cables secured directly to the underside of the joists on the right are found at the “meets Code requirements” end of the spectrum.

Lastly, the green 6 AWG grounding electrode conductor (GEC) in the middle of the photo — loosely run through the basement — would be found at the “does not meet Code minimum” end of the spectrum,  based on the requirements in Sec. 250.64(B)(1).

How About a Show of Support?

Somebody needs to have a discussion with this installer about the Code requirements for using 3/8-in. flexible metal conduit (FMC). Generally speaking, 3/8-in. FMC is not supposed to be used unless permitted by Sec. 348.20(A). For this installation, 348.20(A)(2)(a) would allow installers to use up to 6 ft of 3/8-in. FMC to connect these motors. While the length of this FMC may not be a problem, the lack of supporting means certainly is. Section 348.30(A) requires FMC to be securely fastened within 12 in. of the conduit terminations and at intervals not exceeding 4½ ft.

Perhaps the installer was trying to apply one of the four exceptions noted in Sec. 348.30(A). Unfortunately, none of those exceptions are applicable to this installation. Exception No. 1 does not apply, since the FMC was not fished in. Exception No. 2 has no provisions for
3/8-in. FMC. Exception No. 3 does not apply because the FMC was used for wiring motors, not luminaires. Lastly, Exception No. 4 is not applicable because this installation is not above an accessible suspended ceiling.

I wonder if the installer remembered to install an equipment grounding conductor (EGC) as required by Sec. 348.60? Probably not. And don’t even get me started on the lack of EMT supports.

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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