Transformer Question

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mwdavis3

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Chattanooga, TN USA
Ok, so I have attached a quick sketch of what I am facing. Utility provides 4 wire 208V off their loop (the utility transformer is at substation). Bring it into the building. Hits a large Square D breaker. Neutral does not leave the breaker cabinet enclosure. Neutral is bonded to enclosure and ground here (Service Entrance Bond). Customer wants a Delta/Wye, step up transformer, 208/480. The load is a fire pump. The fire pump is 480V. I know we will ground and bond the transformers secondary neutral (WYE), and then extend the EGC to the fire pump controller. Question: Do we break the neutral to ground connection at the Square D Breaker enclosure and just extend the ECC to this enclosure from the transformer primary? It seems if we leave it, then we have 2 Neutral to Ground bonds because the transformer case is bonded to the neutral. Am I overthinking this?
 

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You are over thinking this. The 208 service needs to be bonded and so does the separately derived 480 Y just like you show it.
You are going to have to consider the requirements of 695 as to OCPD devices for this.
 
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