Service question?

[Selleathy]

I am running a project in oklahoma adding a building to an industrial plant, a pad mounted transformer brings in a 400 amp 277/480 service to a fusible 400 amp disconnect then feeding a 400 amp 277/480 panel with a 100 amp breaker bolted to the bus bars feeding a little transformer for a 225 amp low voltage panel. The vice president of the construction team of this industrial company says he wants more breakers so he proposes bringing two sets of 500 out of the load side of the disconnect one for the existing 400 amp panel and one set to another 400 amp panel he wants me to add, his reasoning is "it wont exceed 400 amps because if it does it will blow the fuse. I told him I dont feel comfortable doing that, its a design build job and they dont know what machines they are adding in the building so its not really possible to do a demand load calculation. Having been brought up in the trades as far as I am concerned you should NEVER blow a main fuse or breaker if you do something is wrong personally I dont think you should be able to trip it with a load PERIOD, barring anything but a short. I feel that this installation is just asking to blow a main fuse. Is there any code violation doing this besides a load calc?

 

[iwire]

Assuming the calculated load is under 400 amps there is absolutely nothing wrong with what the Vice President is suggesting.

Seriously nothing at all.

 

[ActionDave]

I agree with iwire. There is nothing wrong with the VPs idea.

@ Selleathy, You say this is a design build and there is no way to do a load calc. How did you come up with a 400A service? Your stuck staying under 400A as part of the design no matter what, the number of breaker panels won't change this.

 

[iwire]

its not really possible to do a demand load calculation.

I overlooked this due to the lack of spacing.

Then code wise you can't install anything.

I understand there is a real world but if you don't know the load you are just as likely to blow a fuse with one panel as two panels.