separately derived system

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Ragin Cajun said:
Note, all I have to go on is the photo they sent me.

All the green wires are interconnected
One originates at the 3000A 480V switch gear feeding the transformer.
The other go to the new 120/208V panelboard.
Apparently since they could not find any building steel, etc. the grounding electrode conductor, conduit, etc. were not run shown in the detail below. I don't know what more that can be done.


View attachment 2563524
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It seems to me the diagram shows a bonding jumper between N and G at two places. Is this allowed?
 
Looks like I will make them follow the detail for the GEC going to "Building steel, ground grid, water pipe, ETC". The riser calls for a #4 GEC so that should be ample.
They can also to to one of the existing transformers or a new MCC to connect the GEC.
Seems the electrician didn't follow the two details fully.
Why do I get the jobs that don't fit the norm?
Maybe I can finely put this to bed!

And the kicker is I have used these details numerous time on this project over 15 years and never an issue until now!

Thanks for all your help!!

RC
 
petersonra said:
It seems to me the diagram shows a bonding jumper between N and G at two places. Is this allowed?
Click to expand...
Good catch. One location only. SDS or the panel.
Ragin Cajun said:
But the table for conductors #2 or smaller lists #8. The primary conductors are #4. Table 250.102(c)(1) OR 250.66. what did I miss?
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You size the GEC and SSBJ based on the secondary conductor size or in this case 1/0.

I like the verbage of 250.102 (C) (1).
"Size of the Largest Ungrounded Conductor or Equivalent Area for Parallel Conductors"
For me the key words in both tables is Largest Ungrounded. This tells me to size based on the secondary conductors in this case. There ungrounded until grounded either by accident or intentionally. In this case intentionally by using a GEC to an NEC Approved Grounding Electrode system(250.50) comprised of listed electrodes in 250.52
 
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