(B) Protection. Nonheating power supply leads shall be enclosed in a rigid conduit, intermediate metal conduit, electrical metallic tubing, or other approved means.
426.24 Electrical Connection.
(A) Heating Element Connections. Electrical connec- tions, other than factory connections of heating elements to nonheating elements embedded 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 110.14 and 300.15.
426.25 Marking. Each factory-assembled heating unit
shall be legibly marked within 75 mm (3 in.) 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 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.
426.28 Equipment Protection. Ground-fault protection of equipment shall be provided for fixed outdoor electric de-icing and snow-melting equipment, except for equipment that employs mineral-insulated, metal- sheathed cable embedded in a noncombustible medium.
IV. Impedance Heating
426.30 Personnel Protection. Exposed elements of im- pedance heating systems shall be physically guarded, isolated, or thermally insulated with a weatherproof jacket to protect against contact by personnel in the area.
426.31 Isolation Transformer. A dual-winding trans- former with a grounded shield between the primary and secondary windings shall be used to isolate the distribution system from the heating system.
426.32 Voltage Limitations. Unless protected by ground-fault circuit-interrupter protection for personnel, the secondary winding of the isolation transformer connected to the impedance heating elements shall not have an output voltage greater than
30 volts ac.
Where ground-fault circuit-interrupter protection
for personnel is provided, the voltage shall be
permitted to be greater than 30 but not more than 80
volts.
426.33 Induced Currents. All current-carrying compo- nents shall be installed in accordance with 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 a designated point(s).
V. 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 abovegrade. Outdoor pull boxes shall be of watertight construction.
426.42 Single Conductor in Enclosure. The provisions of
300.20 shall not apply to the installation of a single con-
ductor in a