several types of cable running through a floor

What's Wrong Here?

What’s Wrong Here? Hint: Floor Penetration Problem

Dec. 8, 2022

Think you know how this installation violates the NEC?

Hint: Floor penetration problems

There are several types of cable running through the hole in this floor including NM cables and AC cable. When NM cable is run through a hole in the floor, Sec. 334.15(B) requires the cable to be protected from damage by installation in rigid metal conduit (RMC), intermediate metal conduit (IMC), Schedule 80 PVC conduit, RTRC-XW conduit, or other approved means. The conduit must extend a minimum of 6 in. above the floor. No protective sleeve was used at the floor level here. For AC cables, Sec. 320.12(1) prohibits their installation where subject to physical damage but does not specifically require a protective sleeve at the floor the way Sec. 334.15(B) does for NM cables. However, Sec. 300.4 does require conductors, cables, and raceways to be protected where subject to psychical damage. Section 300.21 requires fire stopping be used to prevent fire, smoke, and other products of combustion from spreading through the opening in the floor.

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.