side rail (Example: 3 inches x 6 inches inside cable tray width x 0.389 = 7.0 square inch fill area. This is the first value in Column 1 of Table 392.9. All succeeding values for larger cable tray widths are identically calculated).
392.9.Number of Multiconductor Cables. Rated 2000 Volts or less, in Cable Trays.
(A)Any Mixture of Cable. (2) Cables Smaller Than 4/0
The allowable fill areas for the different ladder or ventilated trough cable tray widths are indicated in square inches in Column 1 of Table 392.9. The total sum of the
392.9(A)(2)].
392.9.Number of Multiconductor Cables. Rated 2000 Volts or less, in Cable Trays.
(A) Any Mixture of Cables. (3) 4/0 or Larger Cables Installed With Cables Smaller Than 4/0
The ladder or ventilated trough cable tray needs to be divided into two zones (a barrier or divider is not required but one can be used if desired) so that the No. 4/0 and larger cables have a dedicated zone as they are to be placed in a single layer.
The formula for this type of installation is shown in Column 2 of Table 392.9. This formula is a trial and error method of selecting a cable tray of the proper width. A direct method for determining the cable tray width is available by figuring the cable tray widths that are required for each of the cable combinations and then adding these widths together to select the proper cable tray width. [Sd (sum of the diameters of the No. 4/0 and larger cables)] + [Sum of Total Cross Sectional Area of all Cables No. 3/0 and Smaller) x (6 inches/7 square inches)] = The Minimum Width of Cable Tray Required. For an example of the procedure to use in selecting a cable tray width for the type of cable covered in this section,
392.9(A)(3)].
392.9.Number of Multiconductor Cables. Rated 2000 Volts or less, in Cable Trays.
(B)Multiconductor Control and/or Signal Cables Only.
A ladder or ventilated trough cable tray, having a loading depth of 6 inches or less containing only control and/or signal cables, may have 50 percent of its
6),[Example 392.9 (B)].
392.9.Number of Multiconductor Cables, Rated 2000 Volts, Nominal, or Less, in Cable Trays. (C) Solid Bottom Cable Trays Containing Any Mixture.
For solid bottom cable tray, the allowable cable fill area is reduced to approximately 30 percent as indicated by the values in Columns 3 and 4 of Table
392.9.The first value in Column 3 was obtained as follows: 3 in. loading depth x 6 in. inside width x 0.305 = 5.5 square inches. The other values in Column 3 were obtained in a like manner. The Sd term in Column 4 has a multiplier of 1 vs. the multiplier of 1.2 for Column 2.
392.9.Number of Multiconductor Cables, Rated 2000 Volts, Nominal, or Less, in Cable Trays. (C) Solid Bottom Cable Trays Containing any Mixture. (1) 4/0 or Larger Cables
The procedure used in selecting a cable tray width for the type of cable covered in this section is similar to that shown on Appendix Sheet 3 page 47, but only 90 percent of the cable tray width can be used.
Cable Tray Manual | Cooper |
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