Sizing wire for ground bar

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Jennifer K.

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Chicago, IL, USA
Hello - I am looking for feedback (relevant NEC section reference would be great) as how to size the wire which would connect a small ground bar in a small electric room to the main building ground bar (located in the main electric room).
 
Hopefully I understand.
If your small panel is a sub-panel, fed by another panel the equipment ground should be
part of the feeder and sized by 250.122.
If it's a service panel, the grounding electrode conductor would be sized by 250.66 based on the service conductor size.
 
What is being connected to the bar? If it's being used as a common grounding conductor for multiple SDS's the minimum size is #3/0. {250.30(A)(6)}
 
infinity said:
What is being connected to the bar? If it's being used as a common grounding conductor for multiple SDS's the minimum size is #3/0. {250.30(A)(6)}
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There are 2 transformers that would be connected to the smaller ground bar (75KVA and 15KVA); the NEC 250.30(A)(6) section makes sense - thank you, this was exactly what I was looking for.
 
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