severely rusted raceways and electrical wiring

Illustrated Catastrophes: Rusted Raceways

June 1, 2023
See the latest Code violations from NEC Consultant Russ LeBlanc.

All references are based on the 2023 edition of the NEC. 

Rusted Raceways

There is not much left of the flexible metal conduit (FMC) that was originally used to wire the lights and switch for this utility room. Excessive humidity has taken its rusty toll on this equipment. The luminaires and switch box are severely rusted too. Section 300.6 requires raceways, boxes, cabinets, elbows, couplings, fittings, supports, support hardware, and other equipment to be made of materials suitable for the environment where they are installed. Perhaps installing nonmetallic raceways, boxes, and luminaires in this humid environment would have prevented the rapid deterioration of the installation. With the FMC completely rusted out, the bonding and grounding connections required throughout Art. 250 are left in doubt. The lack of an effective ground-fault current path as required by Sec. 250.4(A)(5) could lead to an increased risk of shock if there is no way for fault current to return to the source and trip the breaker. The supports for the box have also rusted through, and the box is now hanging by the wires and rusted FMC. I’m sure this box originally complied with the support requirements of Sec. 314.23, but the way it's dangling now creates a violation.

 Bad Box Support Technique

Supporting a box on a single raceway is generally not permitted, but Secs. 314.23(E) and (F) do provide requirements for using raceways to support boxes. For this installation, Sec. 314.23(E) applies. That section permits boxes 100 cu in. or less that do not support a luminaire or contain a device such as a receptacle or switch to be supported by two or more conduits threaded wrenchtight into the enclosure. Each conduit must then be secured within 3 ft of the enclosure — or within 18 in. if the conduits enter the enclosure on the same side. Another problem I see is the use of a set screw type conduit body. For wet locations such as this rooftop cooling tower location, Sec. 314.25 requires boxes, conduit bodies,  and fittings to be listed for use in wet locations. I’m fairly certain that this “short L” conduit body is not listed for use in a wet location. Upon close examination of the RMC used to support the box, you may notice the hole rusted right through the raceway near the bottom of the 90º bend. The rust is actually so bad that this raceway is in danger of snapping in half! Section 225.22 requires raceways on the exterior of buildings or structures to be arranged to drain and prevent raceways from collecting water and rusting out like this.

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.

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