Re: Circuit type
[EDIT: I am presuming this is a 3-phase, 480-120/208 V system. No voltage levels were given in the question.]
If ?the engineer? used a 225 amp panel to serve 115KVA of computed load (equivalent to 319.4 amps), then I would call it a ?bad design.? It?s not unsafe, just bad. By that I mean that it will not serve the customer?s needs. The main breaker would trip under a load that is lower than the computed load. But that is not an NEC issue.
Is the transformer adequately protected? For the secondary, I would say ?yes.? 75KVA equates to 208 amps. Add 25% and you get 260. The 225 amp main breaker on the first panel is lower than 260, so it does not violate the limits of Table 450.3(B). You gave us no information on the primary side protection.
Are the conductors properly sized? We can?t say, because you did not tell us what size(s) ?the engineer? specified.
What?s the bottom line? If I were the owner, I would fire ?the engineer.? But if I were the Inspector, I would have to let it go (unless there are other issues that you have not listed here). I?ve never been an Inspector. I don?t know if your duties and obligations require you to advise the owner that the design ?meets code but is inadequate.? But if they do not prohibit you from doing so, then I would definitely suggest pointing out the design weakness to the owner.
[ January 29, 2004, 04:56 PM: Message edited by: charlie b ]
