Electrical Safety Aspects - Guide to Separation of Network Cabling from EMI Sources

Guide to Separation of Network Cabling from EMI Sources

Electrical Safety Aspects

The “Electrical Safety” aspect is described in the National Electrical Code (NEC) (ANSI/NFPA 70, current
Edition 2005, excerpts below are from 1999 edition) or other locally approved electrical safety codes. It is the law and you must conform to it.

The separation between power and network cabling is described in the NEC Article 800-52
“Installation of Communications Wires, Cables, and Equipment”:

  • (a) “Separation from Other Conductors”:
    • (1) In Raceways, Boxes, and Cables.
      • (a) Other Power-Limited Circuits. Communications cables shall be permitted in the same raceway or enclosure with cables of any of the following:
        • 1) Class 2 and Class 3 remote-control, signaling, and power-limited circuits in compliance with Article 725
        • 2) Power-limited fire alarm systems in compliance with Article 760
        • 3) Nonconductive and conductive optical fiber cables in compliance with Article 770
        • 4) Community antenna television and radio distribution systems in compliance with Article 820
        • 5) Low power network-powered broadband communications circuits in compliance with Article 830
      • b) Class 2 and Class 3 Circuits. Class 1 circuits shall not be run in the same cable with communications circuits. Class 2 and Class 3 circuit conductors shall be permitted in the same cable with communications circuits, in which case the Class 2 and Class 3 circuits shall be classified as communications circuits and shall meet the requirements of this article. The cables shall be listed as communications or multipurpose cables.
Exception: Cables constructed of individually listed Class 2, Class 3, and communications cables under a common jacket shall not be required to be classified as communications cable. The fire-resistance rating of the composite cable shall be determined by the performance of the composite cable.
      • c) Electric Light, Power, Class 1, Nonpower-Limited Fire Alarm, and Medium Power Network-Powered Broadband Communications Circuits.
      • 1. In Raceways, Compartments, and Boxes. Communications conductors shall not be placed in any raceway, compartment, outlet box, junction box, or similar fitting with conductors of electric light, power, Class 1, nonpower-limited fire alarm or medium power network-powered broadband communications circuits.
Exception No. 1: Where all of the conductors of electric light, power, Class 1, nonpower-limited fire alarm, and medium power network-powered broadband communications circuits are separated from all of the conductors of communications circuits by a barrier.
Exception No. 2: Power conductors in outlet boxes, junction boxes, or similar fittings or compartments where such conductors are introduced solely for power supply to communications equipment. The power circuit conductors shall be routed within the enclosure to maintain a minimum of 0.25-in. (6.35 mm) separation from the communications circuit conductors.
    • (2) Other Applications. Communications wires and cables shall be separated at least 2 in. (50.8 mm) from conductors of any electric light, power, Class 1, nonpower-limited fire alarm, or medium power network-powered broadband communications circuits.
Exception No. 1: Where either (1) all of the conductors of the electric light, power, Class 1, nonpowerlimited fire alarm, and medium power network-powered broadband communications circuits are in a raceway or in metal-sheathed, metal-clad, non-metallic-sheathed, Type AC, or Type UF cables, or (2) all of the conductors of communications circuits are encased in a raceway.

Exception No. 2: Where the communications wires and cables are permanently separated from the conductors of electric light, power, Class 1, nonpower-limited fire alarm, and medium power network-powered broadband communications circuits by a continuous and firmly fixed nonconductor, such as porcelain tubes or flexible tubing, in addition to the insulation on the wire.

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