Resolución 2535: adopta el Código Eléctrico Nacional, versión 1993. (Sustituye el Anejo A del Reglamento 4435)

Exception No. 4: For cranes and hoists as permitted by Section 610-14. Exception No. 5: For elevator control and signaling circuits as permitted by Section 620-12. ARTICLE 310 - CONDUCTORS FOR GENERAL WIRING 70-161 Table 310-5. Voltage Rating of Conductor-Volts Minimum Conductor Size-AWG 0 through 2000 14 Copper 12 Aluminum or Copper-Clad Aluminum 2001 through 5000 8 5001 through 8000 6 8001 through 15000 2 15001 through 28000 1 28001 through 35000 1/0 Exception No. 6: For Class 1, Class 2, and Class 3 circuits as permitted by Sections 725-16 and 725-37. Exception No. 7: For fire protective signaling circuits as permitted by Sections 760-16, 760-25, and 760-51. Exception No. 8: For Type V cables, the minimum conductor sizes are: No. 12 for 2000-volt rating, No. 10 for 3000-volt rating, and No. 8 for 4000-volt rating. Exception No. 9: For motor control circuits as permitted by Section 430-72. 310-6. Shielding. Solid dielectric insulated conductors operated above 2000 volts in permanent installations shall have ozone-resistant insulation and shall be shielded. All metallic insulation shields shall be grounded through an effective grounding path meeting the requirements of Section 250-51. Shielding shall be for the purpose of confining the voltage stresses to the insulation. Exception: Nonshielded insulated conductors listed by a qualified testing laboratory shall be permitted for use up to 8000 volts under the following conditions: a. Conductors shall have insulation resistant to electric discharge and surface tracking, or the insulated conductor(s) shall be covered with a material resistant to ozone, electric discharge, and surface tracking. b. Where used in wet locations, the insulated conductor(s) shall have an overall nonmetallic jacket or a continuous metallic sheath. C. Where operated at 5001 to 8000 volts, the insulated conductor(s) shall have a nonmetallic jacket over the insulation. The insulation shall have a specific inductive capacity no greater than 3.6, and the jacket shall have a specific inductive capacity no greater than 10 and no less than 6. d. Insulation and jacket thicknesses shall be in accordance with Table 310-63. 310-7. Direct Burial Conductors. Conductors used for direct burial applications shall be of a type identified for such use. Cables rated above 2000 volts shall be shielded. Exception: Nonshielded multiconductor cables rated 2001-5000 volts shall be permitted if the cable has an overall metallic sheath or armor. 70-162 NATIONAL ELECTRICAL CODE The metallic shield, sheath, or armor shall be grounded through an effective grounding path meeting the requirements of Section 250-51. (FPN No. 1): See Section 300-5 for installation requirements for conductors rated 600 volts or less. (FPN No. 2): See Section 710-4(b) for installation requirements for conductors rated over 600 volts. 310-8. Wet Locations. (a) Insulated Conductors. Insulated conductors used in wet locations shall be (1) lead-covered; (2) Types RHW, TW, THW, THHW, THWN, XHHW; or (3) of a type listed for use in wet locations. (b) Cables. Cables of one or more conductors used in wet locations shall be of a type listed for use in wet locations. Conductors used for direct burial applications shall be of a type listed for such use. 310-9. Corrosive Conditions. Conductors exposed to oils, greases, vapors, gases, fumes, liquids, or other substances having a deleterious effect upon the conductor or insulation shall be of a type suitable for the application. 310-10. Temperature Limitation of Conductors. No conductor shall be used in such a manner that its operating temperature will exceed that designated for the type of insulated conductor involved. In no case shall conductors be associated together in such a way with respect to type of circuit, the wiring method employed, or the number of conductors that the limiting temperature of any conductor is exceeded. (FPN): The temperature rating of a conductor (see Tables 310-13 and 310-61) is the maximum temperature, at any location along its length, that the conductor can withstand over a prolonged time period without serious degradation. The allowable ampacity tables, the ampacity tables of Article 310 and the ampacity tables of Appendix B, the correction factors at the bottom of these tables, and the notes to the tables provide guidance for coordinating conductor sizes, types, allowable ampacities, ampacities, ambient temperatures, and number of associated conductors. The principal determinants of operating temperature are: 1. Ambient temperature. Ambient temperature may vary along the conductor length as well as from time to time. 2. Heat generated internally in the conductor as the result of load current flow. 3. The rate at which generated heat dissipates into the ambient medium. Thermal insulation that covers or surrounds conductors will affect the rate of heat dissipation. 4. Adjacent load-carrying conductors. Adjacent conductors have the dual effect of raising the ambient temperature and impeding heat dissipation. ARTICLE 310 - CONDUCTORS FOR GENERAL WIRING 70-163 310-11. Marking. (a) Required Information. All conductors and cables shall be marked to indicate the following information, using the applicable method described in (b) below. (1) The maximum rated voltage for which the conductor was listed. (2) The proper type letter or letters for the type of wire or cable as specified elsewhere in this Code. (3) The manufacturer's name, trademark, or other distinctive marking by which the organization responsible for the product can be readily identified. (4) The AWG size or circular-mil area. (b) Method of Marking. (1) Surface Marking. The following conductors and cables shall be durably marked on the surface. The AWG size or circular mil area shall be repeated at intervals not exceeding 24 inches (610 mm). All other markings shall be repeated at intervals not exceeding 40 inches (1.02 m). a. Single- and multiconductor rubber- and thermoplastic- insulated wire and cable. b. Nonmetallic-sheathed cable. c. Service-entrance cable. d. Underground feeder and branch-circuit cable. e. Tray cable. f. Irrigation cable. g. Power-limited tray cable. (2) Marker Tape. Metal-covered multiconductor cables shall employ a marker tape located within the cable and running for its complete length. Exception No. 1: Mineral-insulated, metal-sheathed cable. Exception No. 2: Type AC cable. Exception No. 3: The information required in Section 310-11 shall be permitted to be durably marked on the outer nonmetallic covering of Type MC or Type PLTC cables at intervals not exceeding 40 inches (1.02 m). Exception No. 4: The information required in Section 310-11(a) shall be permitted to be durably marked on a nonmetallic covering under the metallic sheath of Type PLTC cable at intervals not exceeding 40 inches (1.02 m). (FPN): Included in the group of metal-covered cables are Type AC cable (Article 333), Type MC cable (Article 334), and lead-sheathed cable. (3) Tag Marking. The following conductors and cables shall be marked by means of a printed tag attached to the coil, reel, or carton: a. Mineral-insulated, metal-sheathed cable. b. Switchboard wires. c. Metal-covered, single-conductor cables. d. Conductors having outer surface of asbestos. e. Type AC cable. 70-164 NATIONAL ELECTRICAL CODE (4) Optional Marking of Wire Size. For the following multiconductor cables, the information required in (a) (4) above shall be permitted to be marked on the surface of the individual insulated conductors: a. Type MC cable. b. Tray cable. c. Irrigation cable. d. Power-limited tray cable. e. Power-limited fire protective signaling cable. (c) Suffixes to Designate Number of Conductors. A type letter or letters used alone shall indicate a single insulated conductor. The following letter suffixes shall indicate the following: D-For two insulated conductors laid parallel within an outer nonmetallic covering. M-For an assembly of two or more insulated conductors twisted spirally within an outer nonmetallic covering. (d) Optional Markings. Conductor types listed in Table 310-13 shall be permitted to be surface marked to indicate special characteristics of the cable materials. (FPN): Examples of these markings include but are not limited to "LS" for limited-smoke and markings such as "sunlight-resistant." 310-12. Conductor Identification. (a) Grounded Conductors. Insulated conductors of No. 6 or smaller, intended for use as grounded conductors of circuits, shall have an outer identification of a white or natural gray color. Multiconductor flat cable No. 4 or larger shall be permitted to employ an external ridge on the grounded conductor. Exception No. 1: Fixture wires as outlined in Article 402. Exception No. 2: Mineral-insulated, metal-sheathed cable. Exception No. 3: A conductor identified as required by Section 210-5(a) for branch circuits. Exception No. 4: Where the conditions of maintenance and supervision assure that only qualified persons will service the installation, grounded conductors in multiconductor cables shall be permitted to be permanently identified at their terminations at the time of installation by a distinctive white marking or other equally effective means. For aerial cable, the identification shall be as above, or by means of a ridge so located on the exterior of the cable as to identify it. Wires having their outer covering finished to show a white or natural gray color but having colored tracer threads in the braid, identifying the source of manufacture, shall be considered as meeting the provisions of this section. (FPN): For identification requirements for conductors larger than No. 6, see