Conductor Derating

[Rodie Radermacher]

Table B.310.11 and the following FPN show how to calculate conductor ampacity for up to 85 conductors in Raceway with Load Diversity. How is ampacity calculated with more than 85 (actually 120) conductors??

 

[flip]

Re: Conductor Derating

I believe the appendix in the back of the code book tells you how to do it. Are you running control circuits??? Special rules apply.

 

[charlie b]

Re: Conductor Derating

Originally posted by Rodie Radermacher:
How is ampacity calculated with more than 85 (actually 120) conductors??

By hiring a licensed PE to run a software package that uses the Neher-McGrath process. Sorry that I can't give a better answer, but I think that this is the only answer.

 

[redfish]

Re: Conductor Derating

Annex B,Table B.310.11

Oops, I think you already knew this. Just call me redundant.

[ July 19, 2005, 06:40 PM: Message edited by: redfish ]

 

[charlie b]

Re: Conductor Derating

Originally posted by flip: I believe the appendix in the back of the code book tells you how to do it.

Originally posted by redfish: Annex B, Table B.310.11

I think the point of the question comes from the FPN located just under that table. It specifically states that the table does not apply, if there are more than 85 conductors. What you need is a calculation that is performed "under engineering supervision." I wasn't kidding with my previous response.

 

[redfish]

Re: Conductor Derating

Once again I'm guilty of not reading the entire article (FPNs included). Just call me consistent. Thanks Charlie.