thumperbs
Member
Hi all my skepticism radar is in full swing and I'm hoping someone more experienced can help me out.
Short story is that I'm currently reviewing a large capital project and specifically looking at the cabinet design and feeder requirements for an enclosure housing eight servo drives, four fractional motor controls and a small control transformer. While reviewing the drawings the size of the feeder seemed very small (#4 behind 70A protection). I crunched all of the numbers and applied NEC to everything and am coming up with needing a feeder suitable for 125A. All branch circuits within seemed to be sized correctly.
I expressed my concerns to the OEM wanting clarification on their numbers and was responded to with scenario specific verbiage as to the reasoning behind their calculations, ie; two of the servos will only run one at a time and all motors were accounted for based on their full load amps. Along with this came "The panel is UL508 listed and we will not be discussing this any further".
How far can I trust this from you more seasoned guys? The system as it is specced seems grossly inadequate to me. Per the NEC, specifically looking at 430.122 in relation to drives and conductor/OCPD sizing, it's illegal as all get out. Most info I have found seems to corroborate with my findings, however I have been told that a UL listing trumps all as well. Making matters worse it looks like I need to fork over $1000 to gain the official codebook for me to verify the UL side of things.
A big thank you to anyone that helps me out on this. I do alot of in house design and have prided myself on never failing an inspection or screwing up big wire pulls. I don't want to start now.
Short story is that I'm currently reviewing a large capital project and specifically looking at the cabinet design and feeder requirements for an enclosure housing eight servo drives, four fractional motor controls and a small control transformer. While reviewing the drawings the size of the feeder seemed very small (#4 behind 70A protection). I crunched all of the numbers and applied NEC to everything and am coming up with needing a feeder suitable for 125A. All branch circuits within seemed to be sized correctly.
I expressed my concerns to the OEM wanting clarification on their numbers and was responded to with scenario specific verbiage as to the reasoning behind their calculations, ie; two of the servos will only run one at a time and all motors were accounted for based on their full load amps. Along with this came "The panel is UL508 listed and we will not be discussing this any further".
How far can I trust this from you more seasoned guys? The system as it is specced seems grossly inadequate to me. Per the NEC, specifically looking at 430.122 in relation to drives and conductor/OCPD sizing, it's illegal as all get out. Most info I have found seems to corroborate with my findings, however I have been told that a UL listing trumps all as well. Making matters worse it looks like I need to fork over $1000 to gain the official codebook for me to verify the UL side of things.
A big thank you to anyone that helps me out on this. I do alot of in house design and have prided myself on never failing an inspection or screwing up big wire pulls. I don't want to start now.