Stumped by the Code? Rules for Supporting Wiring Systems Installed Above Suspended Ceilings

Oct. 16, 2017

Your most pressing National Electrical Code (NEC) questions answered

All questions and answers are based on the 2017 NEC.

Q. What are the Code requirements for supporting wiring systems installed above suspended ceilings?

A. The ceiling‑support wires or ceiling grid aren’t permitted to be used to support raceways and cables (power, signaling, or communications). However, independent support wires that are secured at both ends and provide secure support are permitted [300.11(B)] (Fig. 1).

Www Ecmweb Com Sites Ecmweb com Files Nec Code Quandaries Oct 2017 1

Outlet boxes [314.23(D)] and luminaires can be secured to the suspended-ceiling grid if securely fastened to the ceiling framing members by mechanical means, such as bolts, screws, or rivets — or by the use of clips or other securing means identified for use with the type of ceiling-framing member(s) used [410.36(B)].

Electrical wiring within the cavity of a fire-rated floor-ceiling [300.11(B)(1) or a nonfire-rated ceiling assembly [300,11(B)(2) can be supported by independent support wires attached to the ceiling assembly. The independent support wires must be distinguishable from the suspended-ceiling support wires by color, tagging, or other effective means.

Q. What are the Code rules in regard to raceways used for support of other raceways, cables, or nonelectrical equipment?

A. Raceways aren’t permitted to be used as a means of support for other raceways, cables, or nonelectrical equipment, except as permitted in (1) through (3) [300.11(C)].

(1) Identified. If the raceway or means of support is identified as a means of support.

(2) Class 2 and 3 Circuits. Class 2 and 3 cables can be supported by the raceway that supplies power to the equipment controlled by the Class 2 or 3 circuit (Fig. 2).

(3) Boxes Supported by Raceways. Raceways are permitted as a means of support for threaded boxes and conduit bodies in accordance with 314.23(E) and (F), or to support luminaires in accordance with 410.36(E).

Www Ecmweb Com Sites Ecmweb com Files Nec Code Quandaries Oct 2017 2

Cables aren’t permitted to be used to support other cables, raceways, or nonelectrical equipment [300.11(D)].

Holt is the owner of Mike Holt Enterprises, Inc. in Leesburg, Fla. He can be reached at www.mikeholt.com.

Www Ecmweb Com Sites Ecmweb com Files Uploads 2015 01 Ecm Mini Ad 2014

About the Author

Mike Holt

Mike Holt is the owner of Mike Holt Enterprises (www.MikeHolt.com), one of the largest electrical publishers in the United States. He earned a master's degree in the Business Administration Program (MBA) from the University of Miami. He earned his reputation as a National Electrical Code (NEC) expert by working his way up through the electrical trade. Formally a construction editor for two different trade publications, Mike started his career as an apprentice electrician and eventually became a master electrician, an electrical inspector, a contractor, and an educator. Mike has taught more than 1,000 classes on 30 different electrical-related subjects — ranging from alarm installations to exam preparation and voltage drop calculations. He continues to produce seminars, videos, books, and online training for the trade as well as contribute monthly Code content to EC&M magazine.