Grounded Conductor, Separately Derived System

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NSTech

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Greetings,
I am not finding how to size the Grounded Conductor for a Separately Derived System when the System Bonding Jumper is connected at the source.
250.30(A)(3) indicates sizing for single or parallel raceways when the SBJ "is not located at the source", which is Table 250.102(C)(1).
So.....what if the SBJ IS located at the source? I would think we would still size the neutral according to Table 250.102(C)(1). But if so, why do they specifically give grounded conductor sizing only when the SBJ is at the disconnect? Thanks for any clarification!!
 
Good question. I don't have a section.

Offhand I'd say the grounded conductor must have an ampacity not less than the calculated load (with continuous load factored 120% if connected to OCPD), but not smaller than required for the supply-side bonding jumper.
 
That is a good question. 215.2 provides guidance for feeder neutrals and 250.24 for service neutrals but I can't find a corresponding section for SDS grounded conductor when the bonding jumper is at the source.
I'd tend to agree with Smart$ based on the method it's handled in the 215.2 and 250.24 situation, but likewise I can't confirm that by Code offhand.
 
Thanks for the replies Smart $ and augie 47!
It would not have surprised me that I was missing the obvious so its a big relief that it isn't clear to you guys.
I've probably spent 50 hours preparing to teach a Grounding and Bonding class in Fargo next week....and I spent an additional few hours trying to find the answer to my question before I bothered anyone in the forums. I'll go with the neutral "not smaller" than the SSBJ. Thanks!!
 
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