Table 400.5(A)(2) Type SC cable single conductor derating?

[jnpcook]

Based on the 2011 NEC how would you derate the following:

using 6 single conductor 4/0 cables (90 degree C) running through a conduit or raceway (industrial environment where only qualified persons will service the equipment so can run in raceway per 400.14). Per NEC 400.14 "Where more than three current carrying conductors are installed within the raceway, the allowable ampacity shall be reduced in accordance with Table 400.5(A)(3).

My confusion lies in the fact that Table 400.5(A)(3) is "Adjustment Factors for More Than Three Current-Carrying Conductors in a Flexible Cord or Cable". My cable is not multi conductor, however, but rather 6 separate single conductor tables.

Do I use the D1 column for the single conductor cable and then use the 80 percent derating factor in Table 400.5(A)(3) even though it seems this is the derating factor for a multi-conductor cable containing more than 3 current carrying conductors in it?

I understand the reason for the derating factor due to the increased heat generated by multiple current carrying in a multi conductor cable but I would think that single conductor cables might be derated at a different derating factor as they have more surface area to dissipate the heat generated in them.

Any help would greatly be appreciated.

John

 

[Gregg Harris]

Based on the 2011 NEC how would you derate the following:

using 6 single conductor 4/0 cables (90 degree C) running through a conduit or raceway (industrial environment where only qualified persons will service the equipment so can run in raceway per 400.14). Per NEC 400.14 "Where more than three current carrying conductors are installed within the raceway, the allowable ampacity shall be reduced in accordance with Table 400.5(A)(3).

My confusion lies in the fact that Table 400.5(A)(3) is "Adjustment Factors for More Than Three Current-Carrying Conductors in a Flexible Cord or Cable". My cable is not multi conductor, however, but rather 6 separate single conductor tables.

Do I use the D1 column for the single conductor cable and then use the 80 percent derating factor in Table 400.5(A)(3) even though it seems this is the derating factor for a multi-conductor cable containing more than 3 current carrying conductors in it?

I understand the reason for the derating factor due to the increased heat generated by multiple current carrying in a multi conductor cable but I would think that single conductor cables might be derated at a different derating factor as they have more surface area to dissipate the heat generated in them.

Any help would greatly be appreciated.

John

Wrong article John, look at 310

 

[augie47]

Fist off I would have to say it would take a powerful lot of engineering documentation before I would be comfortable accepting type SC cable for this installation as I see it a violation of 400.8
That said, my first read of the applicable derating sections would lead me to use D1, but that is definitely an uneducated opinion posted mainly to promote discussion.

 

[jnpcook]

Thanks.

Greg, I believe I am looking at the correct article. I did put the cable type in my thread title but failed to mention it in the body of the post. It is Type SC cable which is included in Table 400.5(A)(2).

augie, use is for the connection of utilization equipment to facilitate frequent interchange which is permitted per NEC 400.7 (A) (6).

 

[Gregg Harris]

Thanks.

Greg, I believe I am looking at the correct article. I did put the cable type in my thread title but failed to mention it in the body of the post. It is Type SC cable which is included in Table 400.5(A)(2).

augie, use is for the connection of utilization equipment to facilitate frequent interchange which is permitted per NEC 400.7 (A) (6).

Sorry John, I did not pay atention to the cable type. My opinion would be not compatable for your purpose. Designed for temporary use and is a covered cable and not insulated.

 

[augie47]

Obviously the install would be up to your AHJ, but this is from the manufacturer's data sheet:


For use in accordance with NEC Articles 520, 525, and 530, indoor and outdoor locations