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

Column 1 Column 2* Column 3 Column 4* Inside Applicable Applicable Applicable Applicable Width of for Section for Section for Section for Section Cable 318-9(a)(2) 318-9(a)(3) 318-9(c)(2) 318-9(c)(3) Tray Only Only Only Only (Inches) (Square Inches) (Square Inches) (Square Inches) (Square Inches) 6 7 7-(1.2 Sd)** 5.5 5.5-Sd** 12 14 14 (1.2 Sd) 11.0 11.0-Sd 18 21 21 - (1.2 Sd) 16.5 16.5-Sd 24 28 28 (1.2 Sd) 22.0 22.0-Sd 30 35 35 (1.2 Sd) 27.5 27.5-Sd 36 42 42 (1.2 Sd) 33.0 33.0-Sd For SI units: one square inch = 645 square millimeters. * The maximum allowable fill areas in Columns 2 and 4 shall be computed. For example, the maximum allowable fill, in square inches, for a. 6-inch (152-mm) wide cable tray in Column 2 shall be: 7 minus (1.2. multiplied by Sd). The term Sd in Columns 2 and 4 is equal to the sum of the diameters, in inches, of all Nos. 4/0 AWG and larger multiconductor cables in the same cable tray with smaller cables. (e) Ventilated Channel Cable Trays. Where ventilated channel cable trays contain multiconductor cables of any type, the combined crosssectional area of all cables shall not exceed 1.3 square inches (839 sq mm) in 3-inch (76-mm) wide channel trays, 2.5 square inches (1613 sq mm) in 4-inch (102-mm) wide channel trays, or 3.8 square inches (2452 sq mm) in 6-inch (152-mm) wide channel trays. Exception: Where only one multiconductor cable is installed in a ventilated channel tray, the cross-sectional area of the cable shall not exceed 2.3 square inches (1484 sq mm) in a 3-inch (76-mm) wide channel tray, 4.5 square inches (2903 sq mm) in a 4-inch (102-mm) wide channel tray, or 7.0 square inches (4516 sq mm). in a 6-inch (152-mm) wide channel tray. 70-204 NATIONAL ELECTRICAL CODE 318-10. Number of Single Conductor Cables, Rated 2000 Volts or Less, in Cable Trays. The number of single conductor cables, rated 2000 volts or less, permitted in a single cable tray section shall not exceed the requirements of this section. The single conductors, or conductor assemblies, shall be evenly distributed across the cable tray. The conductor sizes herein apply to both aluminum and copper conductors. (a) Ladder or Ventilated Trough Cable Trays.. Where ladder or ventilated trough cable trays contain single conductor cables, the maximum number of single conductors shall conform to the following: (1) Where all of the cables are 1000 kcmil or larger, the sum of the diameters of all single conductor cables shall not exceed the cable tray width. (2) Where all of the cables are from 250 kcmil up to 1000 kcmil, the sum of the cross-sectional areas of all single conductor cables shall not exceed the maximum allowable cable fill area in Column 1 of Table 318-10, for the appropriate cable tray width. (3) Where 1000 kcmil or larger single conductor cables are installed in the same cable tray with single conductor cables smaller than 1000 kcmil, the sum of the cross-sectional areas of all cables smaller than 1000 kcmil shall not exceed the maximum allowable fill area resulting from the computation in Column 2 of Table 318-10, for the appropriate cable tray width. (4) Where any of the conductor cables are Nos. 1/Q, through 4/0, the sum of the diameters of all single conductor cables shall not exceed the cable tray width, and they shall be installed in a single layer. (b) Ventilated Channel Cable Trays. Where 3-inch (76-mm), 4-inch (102-mm), or 6-inch (152-mm) wide ventilated channel cable trays contain single conductor cables, the sum of the diameters of all single conductors shall not exceed the inside width of the channel. 318-11. Ampacity of Cables, Rated 2000 Volts or Less, in Cable Trays. (a) Multiconductor Cables. The ampacity of multiconductor cables, nominally rated 2000 volts or less, installed according to the requirements of Section 318-9, shall comply with the allowable ampacities of Tables 310-16 and 310-18. The derating factors of Article 310, Note 8(a) of the Notes to Ampacity Tables of 0 to 2000 Volts shall apply only to multiconductor cables with more than three current-carrying conductors. Derating shall be limited to the number of current-carrying conductors in the cable and not to the number of conductorsin the cable tray. Exception No. 1: Where cable trays are continuously covered for more than 6 feet (1.83 m) with solid unventilated covers, not over 95 percent of the allowable ampacities of Tables 310-16 and 310-18 shall be permitted for multiconductor cables. Exception No. 2: Where multiconductor cables are installed in a single layer in uncovered trays, with a maintained spacing of not less than one cable diameter between cables, the ampacity shall not exceed the allowable ambient temperature corrected ampacities of multiconductor cables, with not more than three insulated conductors rated 0-2000 volts in free air, in accordance with Section 310-15(b). (FPN): See Table B-310-3 in Appendix B. ARTICLE 318 - CABLE TRAYS 70-205 Table 318-10. Allowable Cable Fill Area for Single Conductor Cables in Ladder or Ventilated Trough Cable Trays For Cables Rated 2000 Volts or Less Maximum Allowable Fill Area in Square Inches for Single Conductor Cables in Ladder or Ventilated Trough Cable Trays Inside Column 1 Column 2* Width Applicable Applicable of for Section for Section Cable 318-10(a)(2) 318-10(a)(3) Tray Only Only (Inches) (Square Inches) (Square Inches) 6 6.50 6.50 - (1.1 Sd)** 12 13.0 13.0 - (1.1 Sd) 18 19.5 19.5 - (1.1 Sd) 24 26.0 26.0 - (1.1 Sd) 30 32.5 32.5 - (1.1 Sd) 36 39.0 39.0 - (1.1 Sd) For SI units: one square inch = 645 square millimeters. *The maximum allowable fill areas. in Column 2 shall be computed. For example, the maximum allowable fill, in square inches, for a 6-inch (152-mm) wide cable tray shall be: 6.5 minus (1.1 multiplied by Sd). **The term Sd in Column 2 is equal to the sum of the diameters, in inches, of all 1000 kcmil and larger single conductor cables in the same ladder or ventilated trough cable tray with small cables. (b) Single Conductor Cables. The derating factors of Article 310, Note 8 (a) of the Notes to Ampacity Tables of 0 to 2000 Volts shall not apply to the ampacity of cables in cable trays. The ampacity of single conductor cables, or single conductors cabled together (triplexed, quadruplexed, etc.), nominally rated 2000 volts or less, shall comply with the following: (1) Where installed according to the requirements of Section 318-10, the ampacities for 600 kcmil and larger single conductor cables in uncovered cable trays shall not exceed 75 percent of the allowable ampacities in Tables 310-17 and 310-19. Where cable trays are continuously covered for more than 6 feet (1.83 m) with solid unventilated covers, the ampacities for 600 kcmil and larger cables shall not exceed 70 percent of the allowable ampacities in Tables 310-17 and 310-19. (2) Where installed according to the requirements of Section 318-10, the ampacities for No. 1/0 through 500 kcmil single conductor cables in uncovered cable trays shall not exceed 65 percent of the allowable ampacities in Tables 310-17 and 310-19. Where cable trays are continuously covered for more than 6 feet (1.83 m) with solid unventilated covers, the ampacities for No. 1/0 through 500 kcmil cables shall not exceed60 percent of the allowable ampacities in Tables 310-17 and 310-19. (3) Where single conductors are installed in a single layer in uncovered cable trays, with a maintained space of not less than one cable diameter between individual conductors, the ampacity of Nos. 1/0 and larger cables shall not exceed the allowable ampacities in Tables 310-17 and 310-19. 70-206 NATIONAL ELECTRICAL CODE (4) Where single conductors are installed in a triangular configuration in uncovered cable trays, with a maintained space of not less than 2.15 times one conductor diameter (2.15 X O.D.) between circuits, the ampacity of Nos. 1/0 and larger cables shall not exceed the allowable ampacities of two or three single insulated conductors rated 0 through 2000 volts supported on a messenger in accordance with Section 310-15(b). (FPN): See Table B-310-2 in Appendix B. 318-12. Number of Type MV and Type MC Cables (2001 Volts or Over) in Cable Trays. The number of cables, rated 2001 volts or over, permitted in a single cable tray shall not exceed the requirements of this section. The sum of the diameters of single conductor and multiconductor cables shall not exceed the cable tray width, and the cables shall be installed in a single layer. Where single conductor cables are triplexed, quadruplexed, or bound together in circuit groups, the sum of the diameters of the single conductors shall not exceed the cable tray width, and these groups shall be installed in single layer arrangement. 318-13. Ampacity of Type MV and Type MC Cables (2001 Volts or Over) in Cable Trays. The ampacity of cables, rated 2001 volts, nominal, or over, installed according to Section 318-12 shall not exceed the requirements of this section. (a) Multiconductor Cables (2001 Volts or Over). The ampacity of multiconductor cables shall comply with the allowable ampacities of Tables 310-75 and 310-76. Exception No. 1: Where cable trays are continuously covered for more than 6 feet (1.83 m) with solid unventilated covers, not more than 95 percent of the allowable ampacities of Tables 310-75 and 310-76 shall be permitted for multiconductor cables. Exception No. 2: Where multiconductor cables are installed in a single layer in uncovered cable trays, with a maintained spacing of not less than one cable diameter between cables, the ampacity shall not exceed the allowable ampacities of Tables 310-71 and 310-72. (b) Single Conductor Cables (2001 Volts or Over). The ampacity of single conductor cables, or single conductors cabled together (triplexed, quadruplexed, etc.), shall comply with the following: (1) The ampacities for Nos. 1/0 and larger single conductor cables in uncovered cable trays shall not exceed 75 percent of the allowable ampacities in Tables 310-69 and 310-70. Where the cable trays are covered for more than 6 feet (1.83 m) with solid unventilated covers, the ampacities for Nos. 1/0 and larger single conductor cables shall not exceed 70 percent of the allowable ampacities in Tables 310-69 and 310-70. (2) Where single conductor cables are installed in a single layer in uncovered cable trays, with a maintained space of not less than one cable diameter between individual conductors, the ampacity of Nos. 1/0 and larger cables shall not exceed the allowable ampacities in Tables 310-69 and 310-70.