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Issue 9 (Spring 2004) |
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The NEC as a living document
Tom Guida, principal engineer/wire and cable, UL USA
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The safety of the electric power, control, and communications systems in dwellings, offices, and industrial buildings in the United States relies heavily on the use of the National Electrical Code (NEC) for an installation standard, as well as laboratory testing standards for safety of the system components.
The NEC is a comprehensive electrical safety model code published by the National Fire Protection Association (www.nfpa.org). The 2002 edition is current. The NEC provides practical safeguarding of persons and property from hazards arising from the use of electricity. More specifically, it covers the installation of electric conductors and equipment in public and private buildings or other structures (including mobile homes, recreational vehicles, and floating buildings), industrial facilities, and other premises (such as yards, carnivals, and parking lots).
The primary emphasis in the NEC is the elimination of the possibility of electrical shock and fire.
But the NEC also covers installation of optical-fiber cable; however, performance issues, such as data transmission characteristics, are not covered. Because it is a model code, the NEC is not enforceable unless it is adopted, in part or in its entirety, by a local, municipal, county, state, or other authority.
The NEC does not generally cover installations in ships, railway rolling stock, aircraft, automotive vehicles, and underground surfaces and mines. Although communication cables within buildings are covered and, in fact, are a major component of the NEC, communications cable installations outside of buildings and under the control of the communications utility are not covered.
Most installations under the exclusive control of an electric utility are not covered. The precise determination of the line of demarcation between the area controlled by the local authority having jurisdiction (AHJ) and the utility may vary from one locality to another. It is important for installers to be alert, since the requirements of the AHJ and the utility may not be the same.
Three-year cycle
The revision process for the NEC follows the procedures developed by the NFPA. The three-year cycle begins with proposals for revisions of the current edition. Any interested party may make a proposal, which must have the exact wording of the revised or new section and a technical substantiation for the revision.
The task of reviewing proposals falls on the shoulders of roughly 340 volunteer members and alternates, organized into 19 Code-making panels (CMPs) whose primary function is to review proposals for revisions. Each panel is responsible for a particular Article or number of related Articles.
In early December 2002, the CMPs received copies of proposals pertaining to the areas of the NEC for which they are responsible. Proposals were discussed in January 2003 at Code panel meetings and subsequently voted upon by panel members. The NEC Correlating Committee reviews all panel actions for potential conflicts or inconsistencies with other parts of the Code. The 11-member Correlating Committee reviews panel actions to assure that the panels have followed the established NFPA procedures and that significant issues raised in the balloting are addressed. After review by the Correlating Committee, all proposed revisions, whether accepted or rejected, are published in a Technical Committee Report (TCR), which is made available to the public during a comment period of approximately four months. Anyone may comment on actions taken by the CMPs as reported in the TCR. A copy can be obtained online from the NFPA. The comment period for the 2005 NEC has ended.
The Technical Committee Documentation (TCD) and an advanced copy of the new Code will be presented at the NFPA World Fire Safety Congress and Exposition in Salt Lake City in May 2004. NFPA members will then vote on the new Code. After the annual meeting, the NFPA Standards Council issues the revised NEC, with copies expected to be available in September 2004. An appeal procedure is in place for anyone who thinks the revision process has been used improperly or unwisely.
Relevant changes
Significant changes in the NEC that are of particular interest to the communications and signaling industry were accepted during the January 2003 meetings and were discussed by the CMPs in December 2003. These include the addition of new Power Limited Circuit Cable Types CL2D and CL3D; new Fire Alarm Cable Type FPLD; new Optical Fiber Cable Types OFND and OFCD; new Type CATVD and new Communications Cable Type CMD. (Type CMD cables meet the requirements UL presently applies to cable marked “limited combustible” and are being called “duct cable” or “air duct cable.” These cables are suitable for use in ducts, plenums, and other spaces used for environmental air.)
In a related change, the uses for Types CATVP, CMP, OFNP, and OFCP are redefined as “being suitable for use in ceiling cavity plenums and raised floor plenums”. Rules for removing abandoned cable are also being reconsidered.
Unrelated to these changes, the new Network-Powered Broadband Communications Cable Types BL and BLR are added to fill a need for low-power general-purpose and riser coaxial cables.
UL and the NEC
Commonly, NEC users believe it is published by Underwriters Laboratories (UL). This misconception is probably based on the close relationship the NEC has with the UL standards for products manufactured for use in accordance with the Code. UL is a key participant in this constantly evolving Code-writing process, and has a representative on each of the 19 CMPs as well as the Correlating Committee and the Standards Council.
Edited version of the original article of the same title by Cabling Installation & Maintenance, December 2003
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