Code Q&A: Unlisted Communications Cables

Your most pressing National Electrical Code (NEC) questions answered

Sept. 20, 2012

Q. Are unlisted communications cables allowed to enter buildings?

A. Unlisted communications cables can be installed in building spaces other than risers, ducts, or plenum spaces as described in 300.22(C), if the length of the cable within the building from its point of entrance doesn't exceed 50 ft and the cable terminates in an enclosure or primary protector [800.48].

As outlined in Informational Note 2 of 800.48, the primary protector must be located as close as practicable to the point at which the cable enters the building [800.90(B)]. Therefore, unlisted outside plant communications cables may not be permitted to enter the building if it's practicable to place the primary protector closer than 50 ft to the point of entrance.

Remember that the "point of entrance" is defined as the point within the building where the cable emerges from an external wall, from a concrete floor slab, or from rigid metal conduit (RMC) or intermediate metal conduit (IMC) connected to an electrode by a grounding conductor in accordance with 800.100 [800.2].

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.