Cable routing assemblies in the 2011 NEC

Introduced in the latest edition of the National Electrical Code, the cable routing assembly is defined differently than the optical fiber raceway.

Stanley Kaufman, CableSafe Inc.

The National Electrical Code (NEC) is published by the National Fire Protection Association (NFPA; www.nfpa.org) with revisions on a three-year schedule. The 2011 NEC, which replaces the 2008 NEC, was released by NFPA in August 2010. It included many changes of interest to manufacturers, installers and users of communications cable and connectivity products. (NFPA 70, NFPA, the National Fire Protection Association, National Electrical Code and NEC are registered trademarks of the National Fire Protection Association.)

This is the fifth in a series of nine articles, contributed on behalf of the Communications Cable and Connectivity Association (CCCA; www.cccassoc.org), concerning those relevant changes in the NEC. The four preceding articles covered:

• An introduction to the NEC, its scope and organization
• Changes in types and installation rules for data-communications (data/comm) raceways
• Changes in the permitted applications of data/comm cables in air-handling spaces
• Changes in the wiring rules for data/comm cables in riser applications

This article discusses the introduction of cable routing assemblies into the 2011 NEC. Cable routing assemblies are used to support data/comm cables, especially optical fiber cables, in applications with a high density of cables such as a data center. Besides organizing and supporting the cables, cable routing assemblies are designed with gentle bends in order to accommodate the bend-radius restrictions of some designs of optical fiber cables.

Section 770.2 of the 2011 NEC defines optical fiber raceways and cable routing assemblies, as follows.

Optical Fiber Raceway. An enclosed channel of nonmetallic materials designed for holding optical fiber cables in plenum, riser and general-purpose applications.

Cable Routing Assembly. A single channel or connected multiple channels, as well as associated fittings, forming a structural system that is used to support, route and protect high densities of wires and cables, typically communications wires and cables, optical fiber and data (Class 2 and Class 3) cables associated with information technology and communications equipment.

The key difference between raceways (all raceways, not just optical fiber raceways) and cable routing assemblies is that raceways are enclosed and cable routing assemblies may or may not be enclosed. Consequently, manufacturers submitting cable routing assemblies for listing could choose to list enclosed cable routing assemblies as a raceways.

Listing cable routing assemblies

The 2011 NEC has listing requirements for general-purpose and riser cable routing assemblies. The listing requirements for riser cable routing assemblies are identical to the requirements for riser optical fiber and communications raceways in sections 770.182(B) and 800.182(B).

The listing requirements for general-purpose cable routing assemblies are identical to the requirements for general-purpose optical fiber and communications raceways in sections 770.182(C) and 800.182(C).

Applications of cable routing assemblies

General-purpose cable routing assemblies have essentially the same applications as general-purpose optical fiber and communications raceways. Riser cable routing assemblies have essentially the same applications as riser optical fiber and communications raceways.

Because cable routing assemblies are recognized in Article 770 (optical fiber) and Chapter 8 (communications), the 2011 NEC permits their use with optical fiber cables (OFNP, OFCP, OFNR, OFCR, OFNG, OFCG, OFN and OFC), communications cables (CMP, CMR, CMG and CM), CATV cables (CATVP, CATVR and CATV) and network-powered broadband cables (BLP, BLR and BL).

Riser applications of cable routing assemblies permit only riser and plenum cables to be supported by the cable routing assembly. General-purpose applications of cable routing assemblies permit plenum, riser and general-purpose cables to be supported by the cable routing assembly.

Cable routing assemblies are not recognized in Article 725, which includes class 2 data cables, and Article 726, which includes power-limited fire alarm cables.

Section 770.133(B) permits optical fiber cables to be installed in a cable tray, raceway or cable routing assembly along with communications and CATV cables. Section 770.133(C) permits optical fiber cables to be installed in a cable tray or raceway, but not in a cable routing assembly, along with class 2, class 3 and power-limited fire alarm cables.

Section 800.133(A)(1)(a) permits communications cables to be installed in a cable tray, raceway or cable routing assembly along with optical fiber and CATV cables. Section 800.133(A)(1)(b) permits communications cables to be installed in a cable tray or raceway, but not in a cable routing assembly, along with class 2, class 3 and power-limited fire alarm cables.

The 2014 NEC

The primary applications of cable routing assemblies are to support data/comm cables, particularly optical fiber cables, data cables (class 2) and communications cables. While cable routing assemblies have been in use in high-density cable applications like central offices and data centers, they have not been recognized in the NEC until now. Cable routing assemblies were designed for use with optical fiber cables; the 2011 NEC recognizes them in Article 770 (optical fibers). The 2011 NEC also recognizes them for use in communications applications.

Article 645, Information Technology Equipment, is permitted to modify the installation rules for data wiring (class 2 cables) in Article 725; it significantly changes the installation rules for data cable in the raised floor plenum under a computer room. However, it does not have any installation rules for data cables in the equipment space, so the installation rules in Article 725 apply to the installation of data cables in the equipment space in a computer room. The installation of cable routing assemblies is not included in Article 725 in the 2011 NEC.

Given the widespread use of cable routing assemblies in information technology applications, one can expect proposals to be submitted to extend their use to information technology applications covered in Article 725. Proposals to expand the data wiring requirements in Article 645 to include wiring in the equipment space are also likely.

The initial NEC applications of cable routing assemblies were for general-purpose and riser applications. UL 2024, the Underwriters Laboratories standard used for listing cable routing assemblies, has requirements for plenum-grade cable routing assemblies in addition to general-purpose and riser grades. One can expect proposals to recognize plenum-grade cable routing assemblies to be submitted.

The deadline for proposals for the 2014 NEC is November 4, 2011.

My next article will deal with data/comm cable applications.

Author’s disclaimer: This paper, provided by the Communication Cable and Connectivity Association (“CCCA”), is offered for general information and educational purposes. It is not offered, intended, nor should it be relied upon as legal advice. The paper does not set forth the views of any member or any other party, nor may it be taken as such. CCCA makes no warranty regarding the accuracy of the information provided in this paper, and expressly disclaims any implied warranties and any liability for use of the paper or reliance on views expressed in it. CCCA does not endorse, approve, or certify any information set forth in this paper, nor does it guarantee the accuracy, completeness, efficacy, timeliness, or correct sequencing of such information. Use of the paper and the views expressed in it is voluntary, and reliance on it should only be undertaken after an independent review of its accuracy, completeness, efficacy, and timeliness, and based on the individual facts and circumstances of a user.

Stanley Kaufman, Ph.D. is principal of CableSafe Inc. and a consultant to the Communications Cable and Connectivity Association (CCCA; www.cccassoc.org). He is a member of NEC Panel 12 (responsible for Article 645) and Panel 16 (responsible for optical fiber and communications cables).