CEC 15kV TEK Trefoil Arrangement

[elmatador]

Hi Everyone,

I have been trying to determine the proper ampacity derating for TECK Single Conductor cables when arranged in a trefoil arrangement in Cable Tray with 2x the cable diameter spacing between in each trefoil. I cannot seem to apply the 12-2210 rules. Out of all the rules in Rule 12-2210. Only Rule (3) seems to apply to me but unfortunately it derates the cable amapacity from single conductor to three conductor. Does this make sense? Would armoured trefoil arrangement of single conductors reduce it's ampacity to that of a 3C cable? I am confused

See rule below:
12-2210 Ampacities of conductors in cable trays
(1) In ventilated and ladder-type cable trays, where the air space between adjacent conductors, cables, or both
is maintained at greater than 100% of the diameter of the larger conductor or cable, the ampacity of the
conductors or cables shall be the value specified in Item (a) or (b):
(a) single conductors, single-conductor metal-sheathed or armoured cable, and single-conductor
mineral-insulated cable, as specified in Tables 1 and 3; and
(b) multi-conductor cables as specified in Tables 2 and 4, multiplied by the correction factor in Table 5C
for the number of conductors in each cable.
(2) In ventilated and ladder-type cable trays, where the air space between adjacent conductors, cables, or both
is maintained at not less than 25% nor more than 100% of the diameter of the larger conductor or cable,
the ampacity of the conductors or cables shall be the value specified in Subrule (1), multiplied by the
correction factor specified in Table 5D for the arrangement and number of conductors or cables involved,
unless a deviation has been allowed in accordance with Rule 2-030 for other correction factors.
(3) In ventilated and ladder-type cable trays, where the air space between adjacent conductors, cables, or both
is less than 25% of the diameter of the larger conductor or cable, and for any spacing in a non-ventilated
cable tray, the ampacity of the conductors or cables shall be the value as specified in Table 2 or 4 multiplied
by the correction factor specified in Table 5C for the total number of conductors in the cable tray.
(4) In determining the total number of conductors in the cable tray in Subrule (3), Rule 4-004(7) shall apply.
(5) Where cable trays are located in room temperatures above 30 °C, the temperature correction factor of
Table 5A shall be applied to the ampacities determined from Subrules (1), (2), and (3) as applicable.

 

[7anoter4]

The ampacity of cables in cable trays is treated in different way in different standards.
I have no CEC Standard with me. However Alcan co. presents some recommendations[see:]

http://www.stabiloy.com/NR/rdonlyres/14D284B4-23D6-4D82-9B8E-A08FAB0ED764/0/ENInstallHandbook.pdf

I shall try to answer to your question:
“Would armoured trefoil arrangement of single conductors reduce it's ampacity to that of a 3C cable?”
If we don’t take into consideration eddy current induced in single core cable armor[see Rule 4-008]and reduce the ampacity at 70% then the ampacity of single core-cable-even using factor of 0.85 for 3 cable from Table 5B still the ampacity of single core cable is 30% more than for 3 cores
cable. For instance a low voltage cable
For 500 MCM single core 515 A 3cores 330 A[aluminum conductors]
In trefoil arrangement will be 515*0.85=438 A
NEC defines TECK cable as MC cable.
Art.330.80 (A) requires 392.17(A) and (B)
If we’ll compare with NEC Art. 392.17 Ampacity of conductors.
500 MCM for unventilated cable tray reducing factor 0.65
single 545 A [545*.65= 354 A]
3cores 350 [350*.65=227.5 A]