westpennwire.com | 800-245-4964 | [email protected] TECHNICAL REFERENCE 123 The National Electrical Code (NEC) is a set of guidelines written to govern the installation of wiring and equipment in commercial buildings and residential areas. These guidelines were developed to ensure the safety of humans as well as property against fires and electrical hazards. Understanding the National Electrical Code is important for everyone, from the cable manufacturer, engineer and distributor, to the designer and installer. Anyone involved in specifying or installing of cable should be aware of the basics of the code. In 1987, the National Electrical Code introduced some changes that had a major impact on the wire and cable industry. The code now has listing requirements for communication and power-limited circuit cable. These requirements developed fire-resistance levels for cable. The code covers initiation of fire by electronic cable as well as flame spread characteristics of the cable. Code Organization The NEC code book is made up of nine chapters, with each chapter divided into separate articles pertaining to specific subjects. There are about five articles that pertain to communication and power- limited cable. Each article describes wire and cable construction, material use, cable markings, installation environments and applications. Article Categories There are four articles that cover communication, power-limited and CATV wiring. There is another category that deals strictly with optical fiber. The following is a list of those articles and the applications or systems they cover: Article 725 - Class 1, Class 2, Class 3, Remote-control, Signaling and Power-Limited circuits Article 760 - Fire Protective Signaling Systems Article 770 - Fiber Optic Systems Article 800 - Communication Circuits Article 820 - Community Antenna Television Article Overviews The NEC code can be somewhat confusing to the novice who has not studied the code in depth. In most cases, within an article, a listing will allow for a higher listed cable to be substituted for lower listed cable. Or some listings from one article may be substituted for another article listing with possible restrictions. This section will briefly cover the basis of the code to try to make things clearer for you. You should consult the NEC book for exact specifications, wording, and accuracy of the code. This is not in any way an exact excerpt from the code. Article 725 Article 725 covers Class 1, Class 2, and Class 3 remote control and signaling cables, as well as power-limited tray cable. Power-limited tray cable can be used as a Class 3 or Class 2 cable. Cable listed multi-purpose, communications, or power-limited fire protective can be used for Class 2 and Class 3 applications. A Class 3 listed cable can be used as a Class 2 cable. Article 760 Article 760 covers power-limited fire protective cable. Cable listed as power-limited fire protective cable can also be used as Class 2 and Class 3 cable. Cable listed as communications and Class 3 can be used as power-limited fire protective cable with restrictions to conductor material and type, gauge size and number of conductors. Article 770 Article 770 covers fiber optic cable. This article covers three general types: non-conductive, conductive, and composite. Non- conductive type refers to cable containing no metallic members and no other electrically conductive materials. Conductive type refers to cable containing non-current carrying conductive members, such as metallic strength members, etc. Composite type refers to cable containing optical fibers and current carrying electrical conductors. Composite types are classified according to the type of electrical circuit that the metallic conductor is designed for. Article 800 Article 800 covers multi-purpose and communication cable. Multi-purpose cable is the highest listing for a cable and can be used for communication, Class 2, Class 3, and power-limited fire protective cable. Communication cable can be used for Class 2 and Class 3 cable and also as a power-limited fire protective cable with restrictions. Article 820 Article 820 covers community antenna television and RF cable. CATV cable may be substituted with multi-purpose or communication listed coaxial cable. Designation and Environmental Areas Not only does listing by circuit types have to be adhered to, but installation in various environments has to also be considered. The NEC has designated four categories for various environments. These will be listed from the highest to the lowest listing. A higher listing can be used as a substitute for a lower listing. Plenum - This listing is suitable for use in ducts, plenums and other spaces used for environmental air without conduit and has adequate fire-resistant and low-smoke producing characteristics. Riser - This listing is suitable for use in a vertical run, in a shaft or from floor to floor, and has fire-resistant characteristics capable of preventing the carrying of fire from floor to floor. General Purpose - This listing is suitable for general-purpose use, with the exception of risers, ducts, plenums, and other space used for environmental air, and is resistant to the spread of fire. Restricted Applications - This listing is for limited use and is suitable for use in dwellings and raceways and is flame retardant. Restricted use is limited to non-concealed spaces of 10 feet or less, fully enclosed in conduit or raceway, or cable with diameters less than .25 in for a residential dwelling. SPECIAL NOTES FOR COMMUNICATION CABLES: * MULTI-CONDUCTOR CABLES WITH 24-16 AWG CONDUCTORS CAN BE RATED UL AND cUL. * MULTI-CONDUCTOR CABLES WITH 14-8 AWG CONDUCTORS ARE UL LISTED ONLY * 10-8 AWG SPEAKER CABLES ARE CL2 ONLY AND MUST INDICATE AUDIO USE ONLY Technical Reference: NEC Code
