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Hey guys or gals! I'm currently installing a new 400 amp 277/480 service. I'll be feeding a 240 volt, 3 phase, delta transformer for a "sub" panel fed from my I-line panel. My question is would you bond the equipment ground to the neutral in the sub panel or just do it in the transformer. I've been told to bond the the equipment ground to the bonding jumper wire in the transformer and not the sub panel but I'm not sure this is right. Any thoughts?
 

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Code wise, the bonding can be done at either location. I always prefer to do all of the neutral bonding in the transformer as there is usually more room. Some AHJs specify which location (panel or transformer) where the neutral bonding must be located.
 

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Hey guys or gals! I'm currently installing a new 400 amp 277/480 service. I'll be feeding a 240 volt, 3 phase, delta transformer for a "sub" panel fed from my I-line panel. My question is would you bond the equipment ground to the neutral in the sub panel or just do it in the transformer. I've been told to bond the the equipment ground to the bonding jumper wire in the transformer and not the sub panel but I'm not sure this is right. Any thoughts?
If it is a new service then the MAIN panel or the enclosure that houses the primary disconnect for the service is the location to attach...physically, the grounding electrode conductor to the neutral. It is also important to understand the difference between "BONDING" and "GROUNDING". Grounding is the physical connecting of the grounding conductor to the "EARTH" via a rod...a grid...a UFER...etc. BONDING, in electrical terms, means to attach all metallic components of an electrical system together and they all (components) are at the ground potential.
 
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