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Thread: 2 services on one house??

  1. #1
    Join Date
    Aug 2008

    2 services on one house??

    A homeowner is building a large house on a property that already has a smaller existing house on it. The engineer wants to locate the large service for the new house (600 amp) on the existing house and feed the new house with a 600 amp feeder from the new service and also keep the existing service for the existing house. The engineer says 230.2 allows this installation since the new service does not serve the existing house as stated in 230.2; it is just mounted there. I see his point, but wonder is this the intent of 230.2? I suggested several options to eliminate the extra service, but he wants it this way.

  2. #2
    Join Date
    Feb 2003
    Seattle, WA
    Fundamentally, I see nothing wrong with the concept. If the new service does not supply any loads within the existing building, then you are not in conflict with 230.2. But I am slightly confused about the execution.
    1. When you say that the service will be mounted on the existing building, what exactly will that entail? What will be mounted? The utility meter? A (fused or unfused) disconnect?
    2. If the utility's point of common coupling is at the equipment on the existing house, then what will protect the 600 amp feeder to the new house?
    3. Will the new service equipment at the existing house be connected to the existing grounding electrode system?
    4. Will there be an N-G bond within the new service equipment at the existing house?
    Charles E. Beck, P.E., Seattle
    Comments based on 2017 NEC unless otherwise noted.

  3. #3
    Join Date
    Jun 2017
    WI, USA
    Questions charlie has are indeed curios. Otherwise, nothing wrong with mounting it on the other structure.

  4. #4
    Join Date
    May 2005
    Richmond, Virginia
    Without knowing details, it almost seems to make more sense to re-feed the old house from the new house.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

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