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Thread: Grounded Conductor from Power Company Transformer

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    Grounded Conductor from Power Company Transformer

    We have an industrial customer who is having the Power Company replace a 480 volt 3 Phase 3 Wire Delta transformer with a 277/480 Volt 3 Phase 4 Wire Wye Transformer. The customer has their own Electricians, but want our Company to help them with upgrading the Service Conductors and termination. This is a Customer Owned Service from the Power Company's Transformer into the facility. Their electricians are indicating they do not need the grounded conductor ran with the phase conductors, as they do not want to increase the size of the existing conduits. We are hesitant on this installation, because we feel the grounded conductor needs to be installed in order to clear a fault. Are we correct in our interpretation? Thank you for your help!

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    The grounded conductor is required for a 480Y/277 volt service. It can be smaller when sized according to 230.42(C).

    Welcome to the Forum.
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

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    And there is also 250.24(C)

    Roger
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    A perhaps useful question is 'where can the grounded conductor stop and egc only be run with the phase conductors'?

    If a load doesn't require a neutral, you don't have to run it. If the facility was previously supplied with a delta, then nothing uses the grounded conductor as a supply conductor. The only reason for the grounded conductor in this case is fault clearance.

    -Jon

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    Quote Originally Posted by Ranger519 View Post
    We have an industrial customer who is having the Power Company replace a 480 volt 3 Phase 3 Wire Delta transformer with a 277/480 Volt 3 Phase 4 Wire Wye Transformer. The customer has their own Electricians, but want our Company to help them with upgrading the Service Conductors and termination. This is a Customer Owned Service from the Power Company's Transformer into the facility. Their electricians are indicating they do not need the grounded conductor ran with the phase conductors, as they do not want to increase the size of the existing conduits. We are hesitant on this installation, because we feel the grounded conductor needs to be installed in order to clear a fault. Are we correct in our interpretation? Thank you for your help!
    Was the old xformer corner grounded or ungrounded? Is the POCO grounding the new xformer X0 point (very likely)?
    If the POCO is supplying a grounded Y then you must bring the neutral to the service disconnect. If you old system was corner grounded this is going to be a big problem.

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    POCO is the key ! Locally we have had a few of those situations and POCO did not ground XO at there transformer thus it remained an ungrounded system.
    Not sure if that has effect on their transformer and obviously itys up to your POCO but if they ground XO you must bring it to the service by Code as mentioned above.
    At my age, I'm accustomed to restaurants asking me to pay in advance, but now my bank has started sending me their calendar one month at a time.

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