FIXED OUTDOOR DEICING

70-379 in masonry or asphalt or on exposed surfaces, shall be made with insulated connectors identified for the use. (b) Circuit Connections. Splices and terminations at the end of the nonheating leads, other than the heating element end, shall be installed in a box or fitting in accordance with Sections 110-14 and 300-15. 426-25. Marking. Each factory-assembled heating unit shall be legibly marked within 3 inches (76 mm) of each end of the nonheating leads with the permanent identification symbol, catalog number, and ratings in volts and watts, or in volts and amperes. 426-26. Corrosion Protection. Ferrous and nonferrous metal raceways, cable armor, cable sheaths, boxes, fittings, supports, and support hardware shall be permitted to be installed in concrete or in direct contact with the earth, or in areas subject to severe corrosive influences, where made of material suitable for the condition, or where provided with corrosion protection identified as suitable for the condition. 426-27. Grounding. (a) Metal Parts. Exposed noncurrent-carrying metal parts of equipment likely to become energized shall be bonded together and grounded in a manner specified in Article 250. (b) Grounding Braid or Sheath. Grounding means, such as copper braid, metal sheath, or other approved means, shall be provided as part of the heated section of the cable, panel, or unit. D. Impedance Heating 426-30. Personnel Protection. Exposed elements of impedance heating systems shall be physically guarded, isolated, or thermally insulated with weatherproof jacket to protect against contact by personnel in the area. vs426-31. Voltage Limitations. The impedance heating elements shall not operate at a voltage greater than 30 volts ac. Exception: The voltage shall be permitted to be greater than 30 volts, but not more than 80 volts, if a ground-fault circuit-interrupter for personnel protection is provided. 426-32. Isolation Transformer. A dual-winding transformer with a grounded shield between the primary and secondary windings shall be used to isolate the distribution system from the heating system. 426-33. Induced Currents. All current-carrying components shall be installed in accordance with Section 300-20. 426-34. Grounding. An impedance heating system that is operating at a voltage greater than 30, but not more than 80, shall be grounded at designated point(s). 70-380 NATIONAL ELECTRICAL CODE E. Skin Effect Heating 426-40. Conductor Ampacity. The current through the electrically insulated conductor inside the ferromagnetic envelope shall be permitted to exceed the ampacity values shown in Article 310, provided it is identified as suitable for this use. 426-41. Pull Boxes. Where pull boxes are used, they shall be accessible without excavation by location in suitable vaults or above grade. Outdoor pull boxes shall be of watertight construction. 426-42. Single Conductor in Enclosure. The provisions of Section 300-20 shall not apply to the installation of a single conductor in a ferromagnetic envelope (metal enclosure). 426-43. Corrosion Protection. Ferromagnetic envelopes, ferrous or nonferrous metal raceways, boxes, fittings, supports, and support hardware shall be permitted to be installed in concrete or in direct contact with the earth, or in areas subjected to severe corrosive influences, where made of material suitable for the condition, or where provided with corrosion protection identified as suitable for the condition. Corrosion protection shall maintain the original wall thickness of the ferromagnetic envelope. 426-44. Grounding. The ferromagnetic envelope shall be grounded at both ends; and, in addition, it shall be permitted to be grounded at intermediate points as required by its design. The provisions of Section 250-26 shall not apply to the installation of skin effect heating systems. (FPN): For grounding methods, see Section 250-26(d). F. Control and Protection 426-50. Disconnecting Means. (a) Disconnection. All fixed outdoor deicing and snow-melting equipment shall be provided with a means for disconnection from all ungrounded conductors. Where readily accessible to the user of the equipment, the branch-circuit switch or circuit breaker shall be permitted to serve as the disconnecting means. Switches used as the disconnecting means shall be of the indicating type. (b) Cord- and Plug-Connected Equipment. The factory-installed attachment plug of cord- and plug-connected equipment rated 20 amperes or less and 150 volts or less to ground shall be permitted to be the disconnecting means. 426-51. Controllers. (a) Temperature Controller with "Off" Position. Temperature controlled switching devices that indicate an "off" position and that interrupt line current shall open all ungrounded conductors when the control device is in the "off" position. These devices shall not be permitted to serve as the disconnecting means unless provided with a positive lockout in the "off" position.