All questions and answers are based on the 2017 NEC.
Q. What wiring methods does the NEC allow to be installed in a cable tray?
A. Any wiring methods listed in Table 392.10(A) (see Table) can be installed in a cable tray [Sec. 392.10(A)]. Control, signal, and communications cables must be separated from the power conductors by a barrier or maintain a 2-in. separation. This includes:
• Coaxial cables [Sec. 820.133(A)(1)(b), Exception No. 1]
• Class 2 and 3 cables [Sec. 725.136(B) and Sec. 725.136(I)]
• Communications cables [Sec. 800.133(A)(2), Exception No. 1]
• Fire alarm cables [Sec. 760.136(G)]
• Optical fiber cables [Sec. 770.133(B)]
• Intrinsically safe systems cables [Sec. 504.30(A)(2), Exception No. 1]
• Radio and television cables [Sec. 810.18(B), Exception No. 1]
For uses permitted in industrial establishments [Sec. 392.10(B)] where conditions of maintenance and supervision ensure that only qualified persons service the installed cable tray system, single-conductor cables can be installed if (see Figure):
• 1/0 AWG and larger, listed and marked for use in cable trays [Sec. 392.10(B)(1)(a)].
• Equipment grounding conductors (EGCs) must be 4 AWG and larger [Sec. 392.10(B)(1)(c)].
Cable trays in hazardous locations must contain only the cable types and raceways permitted by the Code for the application [Sec. 392.10(C)]. For permitted cable types, see Secs. 501.10, 502.10, 503.10, 504.20, and 505.15.
In addition to the uses permitted elsewhere in Art. 392, nonmetallic cable trays can be installed in corrosive areas, and in areas requiring voltage isolation [Sec. 392.10(D)].
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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.