Generator Switchboard

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infinity

infinity

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I have a large generator, not sure of the size but it's probably over 2000kw. It feeds a generator switchboard which has a few circuit breakers but the generator has no integral OCPD. Also the switchboard is tapped to feed several external disconnects for fire pumps, fire alarm, smoke purge, etc. What code section does the switchboard and conductor length from the generator fall under? Article 445 doesn't mention a length.
 
infinity said:
I have a large generator, not sure of the size but it's probably over 2000kw. It feeds a generator switchboard which has a few circuit breakers but the generator has no integral OCPD. Also the switchboard is tapped to feed several external disconnects for fire pumps, fire alarm, smoke purge, etc. What code section does the switchboard and conductor length from the generator fall under? Article 445 doesn't mention a length.
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Curious, is the prime mover (generator) located "outside the structure" of building served, and only carrying emergency systems (?)
 
augie47 said:
Would 445.13(B)/240.21(B) apply ??
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My initial thinking is if there is nothing in 445, then wouldn't we default to 240.21(B)? As a thought experiment, say there was no 240.21(C) in the code for transformer secondary conductors. Would you then just go by 2:40.21(B)? If so it seems like the generator would be the same.
 
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I'm "nosing around" in Article 700-Emergency Systems : Per description (Office Building) might the structure, fall under listing requirements in 700.12(B)
 
ron said:
I don't know of a length limitation, but I use 10' as the same intent as a tap or a transformer secondary (even though it is not either of those)
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I couldn't find any length directly related to the conductors between the generator and the switchboard. By a quick glance I think the conductors in this case are at least 75' in length.
 
infinity said:
I couldn't find any length directly related to the conductors between the generator and the switchboard. By a quick glance I think the conductors in this case are at least 75' in length.
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I seems to me that if sized to 445.13 (115% nameplate) then there is no length restriction. If you are bringing off multiple sets rated less than nameplate, then I don't see why those wouldn't be considered feeder taps and sized and lengthed per the applicable part of 240.21(B).
 
augie47 said:
Would 445.13(B)/240.21(B) apply ??
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infinity said:
I don't see how 445.15(B) is applicable when the generator has no listed overcurrent protective device or a combination of a current transformer and overcurrent relay.
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electrofelon said:
I seems to me that if sized to 445.13 (115% nameplate) then there is no length restriction. If you are bringing off multiple sets rated less than nameplate, then I don't see why those wouldn't be considered feeder taps and sized and lengthed per the applicable part of 240.21(B).
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Many modern larger generators do incorporate listed overcurrent protection within them.
There's some useful info on pages 7-12 of the following:
https://mishe.starchapter.com/images/downloads/Conference_2019/mishe_2019_genset_controls.pdf

Also see pg. 18 of the following document from Cummins about conductor overload protection:
https://www.cummins.com/sites/defau...tor Set Overcurrent Protection 2020-11-12.pdf
 
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