earmandorobles
Member
- Location
- Mexicali, Mexico
Hi everyone
This is my 3rd topic in this forum and i've had nothing but good answers and very helpful comments. Thanks a lot everyone.
Right now we have a big discussion with a requirement that we had a few years ago by an inspector. He was telling us that we needed to calculate all the feeders according to the expected short circuit value that we had in every panel in a facility. There was no problem with de-rated factors, drop voltage or any other but this short circuit requirement. In that moment we had selected current limiting breakers and we only had to modify a few conductors in order to continue with the design.
Later on we started to look in the NEC and the only article that specifically talks about this matter is Table 240.92 (B) and it reffers only for tap conductors and that article its only for Supervised Industrial Installations. We couldnt find any other article about this issue and we dont find too much logic in re-size a conductor for a 10 HP motor from 10 AWG to 1/0 AWG just because we have a bit more than 40 KA (our circuit breaker is 65 KA and is already a current limiting breaker by manufacture but what would happened if it wasnt a current limiting breaker).
I think that this could be a missinterpretation of this article (either for the inspector or from us) but its an internal discussion and we havent been able to get to a concrete answer (either this applies in every situation or just in some cases like tap conductors)
I hope i made myself clear, im having a little trouble to find the right words to describe our need (were not from usa but in mexico we use the NOM which is a translation of the NEC).
Regards
This is my 3rd topic in this forum and i've had nothing but good answers and very helpful comments. Thanks a lot everyone.
Right now we have a big discussion with a requirement that we had a few years ago by an inspector. He was telling us that we needed to calculate all the feeders according to the expected short circuit value that we had in every panel in a facility. There was no problem with de-rated factors, drop voltage or any other but this short circuit requirement. In that moment we had selected current limiting breakers and we only had to modify a few conductors in order to continue with the design.
Later on we started to look in the NEC and the only article that specifically talks about this matter is Table 240.92 (B) and it reffers only for tap conductors and that article its only for Supervised Industrial Installations. We couldnt find any other article about this issue and we dont find too much logic in re-size a conductor for a 10 HP motor from 10 AWG to 1/0 AWG just because we have a bit more than 40 KA (our circuit breaker is 65 KA and is already a current limiting breaker by manufacture but what would happened if it wasnt a current limiting breaker).
I think that this could be a missinterpretation of this article (either for the inspector or from us) but its an internal discussion and we havent been able to get to a concrete answer (either this applies in every situation or just in some cases like tap conductors)
I hope i made myself clear, im having a little trouble to find the right words to describe our need (were not from usa but in mexico we use the NOM which is a translation of the NEC).
Regards
