Service Circuit Breaker Question

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360Youth

360Youth

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Location
Newport, NC
I am still researching the situation since a 5 o'clock phone call, but i have a busy weekend and wanted some input. Thanks, in advance.

Here is the scenario: My boss calls me today after driving 3 hours for a series of generator start-ups. One of the many complications/questions he has run into is that the EC has fed the fascilities (I have never seen the job, but I think it is waste water operations for a new housing development) with an 800 amp service and main disconnecting means (parallel 500s) which then feeds a 400 amp "whole-house" ATS with a single set of 500s. Based on a sight-unseen, 5-minute phone conversation, I could not come up with a valid reason for this setup. He says the specs call for an 800 amp ATS. The system needs to corrected electrically before we can sign-off on the genset and ATS. Apparently everything has passed inspections to this point. Am I missing something that allows an 800 amp disconnect to feed 400 amp ATS and panels?
 
360Youth said:
The ATS feeds the entire load. I had asked if there was separate non-generator loads, and he said no.
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My point is how positive are you that the connected load is more than 380A? There may have been a change or the EC did a load calc and set up for what is actually installed or the poco and EC costs to provide 800 weren't much diff than a 400... LOTS of things could have happened between someone reading "incoming service 800A send out an 800A ATS" and the on site EC hooking up (correctly/adequately) what was actually installed.

I
 
BryanMD said:
My point is how positive are you that the connected load is more than 380A? There may have been a change or the EC did a load calc and set up for what is actually installed or the poco and EC costs to provide 800 weren't much diff than a 400... LOTS of things could have happened between someone reading "incoming service 800A send out an 800A ATS" and the on site EC hooking up (correctly/adequately) what was actually installed.

I
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I do not have a problem with the connected load issue. I talked with about that on the phone as far as the 500 kcmil wire size. But my question is having the 400 amp switch with no OCP other than the 800 amp main.
 
360Youth said:
I do not have a problem with the connected load issue. I talked with about that on the phone as far as the 500 kcmil wire size. But my question is having the 400 amp switch with no OCP other than the 800 amp main.
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I believe you are correct. This is not a properly protected switch, if the OCP is twice the rating of the switch it is not protected. 230.90 (A) is the section that I would start with.

(A) Ungrounded Conductor. Such protection shall be provided by an overcurrent device in series with each ungrounded service conductor that has a rating or setting not higher than the allowable ampacity of the conductor. A set of fuses shall be considered all the fuses required to protect all the ungrounded conductors of a circuit. Single-pole circuit breakers, grouped in accordance with 230.71(B), shall be considered as one protective device.
 
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