Standard for Fixed Guideway Transit and Passenger Rail Systems
2-4 Wiring Requirements.
All wiring materials and installations within stations other than for traction power shall conform to requirements of NFPA 70, National Electrical Code®, and, in addition, shall satisfy the requirements of 2-4.2 through 2-4.9.
Materials manufactured for use as conduits, raceways, ducts, boxes, cabinets, equipment enclosures, and their surface finish materials shall be capable of being subjected to temperatures up to 932°F (500°C) for 1 hour and shall not support combustion under the same temperature condition. Other materials when encased in concrete shall be acceptable.
All conductors shall be insulated. Ground wires shall be permitted to be bare. All thicknesses of insulation and all thicknesses of jackets shall conform to NFPA 70, National Electrical Code.
All insulations shall conform to Article 310 of NFPA 70, National Electrical Code, and shall be moisture- and heat-resistant types carrying temperature ratings corresponding to the conditions of application and in no case lower than 194°F (90°C).
Wire and cable constructions intended for use in operating vital train signal circuits, power circuits to emergency lights, and so forth shall pass the flame-propagating criteria of IEEE Standard 383, Standard for Type Tests of Class 1E Electric Cables, Field Splices, and Connections for Nuclear Power Generating Stations. National Electrical Code-type (NEC-type) listed cables suitable for use in plenums shall be permitted to be used in train signal circuits.
All conductors, except radio antennas, shall be enclosed in their entirety in armor sheaths, conduits, or enclosed raceways, boxes, and cabinets except in ancillary areas or other nonpublic areas. Conductors in conduits or raceways shall be permitted to be embedded in concrete or run in concrete electrical duct banks, but they shall not be installed exposed or surface-mounted in air plenums that might carry air at the elevated temperatures accompanying fire-emergency conditions.
Overcurrent elements that are (1) designed to protect conductors serving emergency equipment motors (i.e., pumps, etc.), emergency lighting, and communications equipment, and (2) located in spaces other than the main electrical distribution system equipment rooms shall not depend on thermal properties for operation.
Conductors for emergency lighting, communications, and so forth shall be protected from physical damage by transit vehicles or other normal transit system operations and from fires in the transit system by suitable embedment or encasement, or by routing such conductors external to the interior underground portions of the transit system facilities.
2-4.9 Power Supply for Emergency Ventilation Fans.
See Chapter 4 for power supply for emergency ventilation fans.
Joe Tedesco, NEC Consultant