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

310-2. Conductors. (a) Insulated. Conductors shall be insulated. Exception: Where covered or bare conductors are specifically permitted elsewhere in this Code. (FPN): See Section 250-152 for insulation of neutral conductors of a solidly grounded high-voltage system. (b) Conductor Material. Conductors in this article shall be of aluminum, copper-clad aluminum, or copper unless otherwise specified. 310-3. Stranded Conductors. Where installed in raceways, conductors of size No. 8 and larger shall be stranded. Exception: As permitted or required elsewhere in this Code. 70-160 NATIONAL ELECTRICAL CODE 310-4. Conductors in Parallel. Aluminum, copper-clad aluminum, or copper conductors of size No. 1/0 and larger, comprising each phase, neutral or grounded circuit conductor, shall be permitted to be connected in parallel (electrically joined at both ends to form a single conductor). Exception No. 1: As permitted in Section 620-12(a)(1), Exception. Exception No. 2: Conductors in sizes smaller than No. 1/0 shall be permitted to be run in parallel to supply control power to indicating instruments, contactors, relays, solenoids, and similar control devices provided (a) they are contained within the same raceway or cable; (b) the ampacity of each individual conductor is sufficient to carry the entire load current shared by the parallel conductors; and (c) the overcurrent protection is such that the ampacity of each individual conductor will not be exceeded if one or more of the parallel conductors become inadvertently disconnected. Exception No. 3: Conductors in sizes smaller than No. 1/0 shall be permitted to be run in parallel for frequencies of 360 hertz and higher where conditions (a), (b), and (c) of Exception No. 2 are met. The paralleled conductors in each phase, neutral or grounded circuit conductor shall: (1) Be the same length; (2) Have the same conductor material; (3) Be the same size in circular mil area; (4) Have the same insulation type; (5) Be terminated in the same manner. Where run in separate raceways or cables, the raceways or cables shall have the same physical characteristics. (FPN): Differences in inductive reactance and unequal division of current can be minimized by choice of materials, methods of construction, and orientation of conductors. It is not the intent to require that conductors of one phase, neutral or grounded circuit conductor be the same as those of another phase, neutral or grounded circuit conductor to achieve balance. Where equipment grounding conductors are used with conductors in parallel, they shall comply with the requirements of this section except that they shall be sized in accordance with Section 250-95. Where conductors are used in parallel, space in enclosures shall be given consideration (see Articles 370 and 373). Conductors installed in parallel shall comply with the provisions of Article 310, Note 8(a), Notes to Ampacity Tables of 0 to 2000 Volts. 310-5. Minimum Size of Conductors. The minimum size of conductors shall be as shown in Table 310-5. Exception No. 1: For flexible cords as permitted by Section 400-12. Exception No. 2: For fixture wire as permitted by Section 410-24. Exception No. 3: For fractional horsepower motors as permitted by