Example - nec – Cooper Bussmann CT02MAN User Manual
Page 49
47
Cable Tray Manual
Cooper B-Line, Inc
Appendix Sheet 3
Example - NEC
®
Section 392.9(A)(1)
Width selection for cable tray containing 600 volt multiconductor cables, sizes #4/0 AWG and larger
only. Cable installation is limited to a single layer. The sum of the cable diameters (Sd) must be equal
to or less than the usable cable tray width.
Cable tray width is obtained as follows:
(D)
(N)
Multiply (D) x (N)
Item
List
List Cable
List Number
Subtotal of the
Number
Cable Sizes
Outside
of Cables
Sum of the Cables
Diameter
Diameters (Sd)
1.
3/C - #500 kcmil
2.26 inches
4
9.04 inches
2.
3/C - #250 kcmil
1.76 inches
3
5.28 inches
3.
3/C - #4/0 AWG
1.55 inches
10
15.50 inches
The sum of the diameters (Sd) of all cables (Add Sds for items 1, 2, & 3.)
9.04 inches + 5.28 inches + 15.50 inches = 29.82 inches (Sd)
A cable tray with a usable width of 30 inches is required. For
a 10% increase in cost a 36 inch wide cable tray could be
purchased which would provide for some future cable additions.
Notes:
1. The cable sizes used in this example are a random selection.
2. Cables - copper conductors with cross linked polyethylene insulation and a PVC jacket.
(These cables could be ordered with or without an equipment grounding conductor.)
3. Total cable weight per foot for this installation.
61.4 lbs./ft. (without equipment grounding conductors)
69.9 lbs./ft. (with equipment grounding conductors)
This load can be supported by a load symbol "B" cable tray - 75 lbs./ft.
30" Usable Cable Tray Width
29.82" = Equals Cable Sd
Cross Section Of The Cables And The Cable Tray
3
3
3
3
3
3
3
3
3
3
2
2
2
1
1
1
1