wire from generator terminals

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wyboy

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Our local volunteer fire department received through donation an older 100 KVA generator (3 phase 208 volt). There is no overcurrent on the generator which will be mounted to a trailer. They want to mount a 225 main breaker panel on the trailer to feed receptacles also mounted on the trailer and feed the panel with 4/0 copper from the generator terminals. This install would be allowed if this was a service and the wire was service conductor, but because it is a generator the conductors must meet 445.13 which requires conductors to be sized at 115% of the nameplate on the generator. I can find no exception to this rule even if the conductors land in a single overcurrent device. It seems black and white but it makes no sense to me. The required ampacity of the wire from the nameplate x 1.15 is is 318 amps-a 400 kcmil conductor. Am I reading this section right?
Thanks! :rant:
 
In 2011 there is an exception that indicates "Where the design and the operation of the generator prevent overloading, the ampacity of the conductors shall not be less than 100% of the nameplate current rating of the Generator".

Did this rule change in 2014?

Would the single 225 amp overcurrent device not be a "design" that would prevent the overloading the ampacity of the 4/0 conductor?

JAP>
 
jap said:
In 2011 there is an exception that indicates "Where the design and the operation of the generator prevent overloading, the ampacity of the conductors shall not be less than 100% of the nameplate current rating of the Generator".

Did this rule change in 2014?

Would the single 225 amp overcurrent device not be a "design" that would prevent the overloading the ampacity of the 4/0 conductor?

JAP>
Click to expand...
The exception doesn't say that you can reduce the conductors from the 115% of rated generator output to the rating of the OCPD. It only says you can reduce the conductors from 115% of rated output to 100% of rated output.
 
I see.

So for the exception the conductor would have to be rated for 277 amps, I'm guessing since the OP indicated 318 amps was 1.15 of the nameplate output which is more amperage than the 4/0 is allowed to carry.

Correct?

Or is there a multiplier that must be used prior to utilizing the exception?


JAP>
 
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