800A Panelboard

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NSmithIN

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Valparaiso, IN
The following is shown on a drawing for a new installation of a transformer and panelbard. It looks like the conductor sizing is appropriate. Am I missing anything?


  • Panelboard: 480Y/277V 800A bus with a 800A main breaker. NEMA3R rated.
  • Transformer: 500KVA Primary 12470V Secondary=480Y/277V Primary OCPD=100A fuse link
  • Grounding electrode at transformer: 3/4" dia. Cu clad steel ground rod 10' long GEC:#2/0 AWG Cu
  • Secondary conductors: 3 sets of 3C 300KCMIL THHN Cu (Phase) and 1C 2/0 THHN Cu (Neut); each set pulled in a buried 4" rigid PVC conduit 25' long
  • Grounding electrode at panelboard: Building steel that is bonded to plant ground grid GEC: #2/0 AWG Cu

Most loads will be 3W 480V.
 
I think the primary fuse rating is too high. The limit is 300%, and that would be 69 amps. So a 70 amp fuse might be a better choice. Also, absent a calculation of neutral load, I cannot comment on the size of the neutral wire. The rest looks fine to me.
 
Neutral Load

Neutral Load

charlie b said:
I think the primary fuse rating is too high. The limit is 300%, and that would be 69 amps. So a 70 amp fuse might be a better choice. Also, absent a calculation of neutral load, I cannot comment on the size of the neutral wire. The rest looks fine to me.
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There is no neutral load to speak of. All loads will be 3W 480V.
 
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