392.10.Number of Single Conductor Cables, Rated 2000 Volts or Less in Cable Trays. (B) Ventilated Channel Cable Trays.
The sum of the diameters (Sd) of all single conductors shall not exceed the inside width of the ventilated cable channel.
Number Of 600 Volt Single Conductor Cables That May Be Installed In A Ventilated Channel Cable Tray - Section 392.10(B)
Single | Diameter | 3 Inch | 4 Inch | 6 Inch |
Conductor | Inches | V. Channel | V. Channel | V. Channel |
Size | (Note #1) | C.T. | C.T. | C.T. |
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1/0 AWG | 0.58 | 5 | 6 | 10 |
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2/0 AWG | 0.62 | 4 | 6 | 9 |
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3/0 AWG | 0.68 | 4 | 5 | 8 |
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4/0 AWG | 0.73 | 4 | 5 | 8 |
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250 Kcmil | 0.84 | 3 | 4 | 7 |
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350 Kcmil | 0.94 | 3 | 4 | 6 |
500 Kcmil | 1.07 | 2 | 3 | 5 |
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750 Kcmil | 1.28 | 2 | 3 | 4 |
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1000 Kcmil | 1.45 | 2 | 2 | 4 |
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Notes:
#1. Cable diameter's used are those for Okonite- Okolon 600 volt single conductor power cables.
#2. Such installations are to be made only in qualifying industrial facilities as per Sections 392.3(B) & (B)(1).
#3. The phase, neutral, and EGCs cables are all counted in the allowable cable fill for the ventilated channel cable tray.
#4. To avoid problems with unbalanced voltages, the cables should be bundled with ties every three feet or four feet. The bundle must contain the circuit's three phase conductors plus the neutral if one is used. If a cable is used as the EGC, it should also be in the cable bundle. If the designer desires, the ventilated channel cable tray may be used as the EGC as per Table 392.7(B)(2).
#5. The single conductor cables should be firmly tied to the ventilated channel cable tray at six foot or less intervals.
392.11.Ampacity of Cables Rated 2000 Volts or Less in Cable Trays.
(A) Multiconductor Cables.
Ampacity Tables 310.16 and 310.18 are to be used for multiconductor cables which are installed in cable tray using the allowable fill areas as per Section
Cooper B-Line, Inc
392.9.The ampacities in Table 310.16 are based on an ambient temperature of 30˚ Celsius. Conduit and cable tray wiring systems are often installed in areas where they will be exposed to high ambient temperatures. For such installations, some designers and engineers neglect using the Ampacity Correction Factors listed below the Wire Ampacity Tables which results in the conductor insulation being operated in excess of its maximum safe temperature. These correction factors must be used to derate a cable for the maximum temperature it will be subjected to anywhere along its length.
392.11(A)(1)
Section 310.15(B)(2)(a) refers to Section 392.11 which states that the derating information of Table 310.15(B)(2)(a) applies to multiconductor cables with more than three current carrying conductors but not to the number of conductors in the cable tray.
392.11(A)(2)
Where cable trays are continuously covered for more than 6 feet (1.83m) 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.
This is for multiconductor cables installed using Table 392.16 or 392.18. If these cables are installed in cable trays with solid unventilated covers for more than 6 feet the cables must be derated. Where cable tray covers are to be used, it is best to use raised or ventilated covers so that the cables can operate in a lower ambient temperature.
392.11(A)(3)
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
By spacing the cables one diameter apart, the engineer may increase the allowable ampacities of the cables to the free air rating as per Section 310.15(C) and Table
Cable Tray Manual
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