Cooper Bussmann CT02MAN - Manual (Page 35)

33
Cable Tray Manual Cooper B-Line, Inc
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 cross-sectional areas of all the
cables to be installed in the cable tray must be equal
to or less than the cable tray allowable fill area. For
an example of the procedure to use in selecting a
cable tray width for the type of cable covered in this
section
see page 48 (Appendix Sheet 4), [Example
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
Lar ger 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,
see page 49, (Appendix Sheet 5), [EXAMPLE
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 cross-sectional area filled with cable. If the
cable tray has a loading depth in excess of 6 inches,
that figure cannot be used in calculating the
allowable fill area as a 6 inch depth is the maximum
value that can be used for the cross-sectional area
calculation. For an example of the procedure to use
in selecting a cable tray width for the type of cable
covered in this section,
see page 50 (Appendix Sheet
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.