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    New Service upgrade

    Increasing 200 amp service to accommodate 48KW in tankless water heaters.
    Total demand after calc is 287 amps.
    Using a 400amp rated meter/ main with two 200 amps breakers to two interior panels. Generally I’ll install GEC to two ground rods and exterior cold water hose bib continuous with whatever size table 250.66 calls for. No hose bib near the service. I figure by 250.66 I need a 1/0. I am considering running the 1/0 to the water heater in garage, and just a #6 bare to the two ground rods. Any thoughts on code compliance.

    #2
    Check your actual service conductor size (POCO) as 1/0 might be overkill.
    Do you have a metallic underground water supply line ? If so, your grounding electrode conductor must connect withing 5 ft of point of entry of the water line.
    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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      #3
      When I do this, I leave the existing disconnect and panel in place, change the meter base, add the second disconnect, feeder, and panel, and add grounding suitable for 200a (new #4 to same water pipe as existing #4, new #6 split-bolted to existing #6 to existing rods) to the new disconnect.
      Master Electrician
      Electrical Contractor
      Richmond, VA

      Comment


        #4
        Originally posted by LarryFine View Post
        When I do this, I leave the existing disconnect and panel in place, change the meter base, add the second disconnect, feeder, and panel, and add grounding suitable for 200a (new #4 to same water pipe as existing #4, new #6 split-bolted to existing #6 to existing rods) to the new disconnect.
        Yes that will work as well, but existing was a 200amp meter/ main.

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          #5
          Originally posted by augie47 View Post
          Check your actual service conductor size (POCO) as 1/0 might be overkill.
          Do you have a metallic underground water supply line ? If so, your grounding electrode conductor must connect withing 5 ft of point of entry of the water line.
          Parallel 3/0 to mains, equivalent size would put the GEC In the 3/0 to 350 line on the table.
          I would be with in 5ft since the pipe runs into the house slab, but not the primary entry I don’t think.

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            #6
            Originally posted by pfactor2 View Post
            Yes that will work as well, but existing was a 200amp meter/ main.
            Aha. Here in Va, the POCO provides meter bases free, so meter-mains are rare. I've actually never installed one in over 40 years, but I have seen a couple. I wonder how much it would cost to replace the meter-main with a separate meter base and one or two main disconnects.

            The local orange and blue stores sell main breakers in enclosures for around $125 (supply houses can't even find the item number - you have to but the breaker and enclosure separately), so a free meter base and two main discos supplying two ML panels makes the choice easy.
            Master Electrician
            Electrical Contractor
            Richmond, VA

            Comment


              #7
              Originally posted by augie47 View Post
              Check your actual service conductor size (POCO) as 1/0 might be overkill.
              Do you have a metallic underground water supply line ? If so, your grounding electrode conductor must connect withing 5 ft of point of entry of the water line.
              Service drop or lateral conductor size might be irrelevant, it needs to be based on "service entrance conductor" or what would be equivalent if there isn't an actual art 310 conductor. If POCO runs single 350 aluminum to a meter but he runs two 4/0 aluminum to service disconnecting means, his service entrance conductors are the two 4/0 aluminum conductors aren't they whether paralleled or to separate 200 amp disconnects?

              I do agree we need to further address what is up with the water line and where it should be bonded.
              I live for today, I'm just a day behind.

              Comment


                #8
                Originally posted by pfactor2 View Post
                Increasing 200 amp service to accommodate 48KW in tankless water heaters.
                Total demand after calc is 287 amps.
                Using a 400amp rated meter/ main with two 200 amps breakers to two interior panels. Generally I’ll install GEC to two ground rods and exterior cold water hose bib continuous with whatever size table 250.66 calls for. No hose bib near the service. I figure by 250.66 I need a 1/0. I am considering running the 1/0 to the water heater in garage, and just a #6 bare to the two ground rods. Any thoughts on code compliance.
                Sounds like a 300A service. We usually run Aluminum for service entrance conductors and CU for the grounding electrode conductor, for a 300A residential 350kCMIL Al service conductors and #2 CU GEC.
                Commercial 300A 500 AL and still a #2 CU.
                A true 400A service around here would need a C.T can, and parallel 250's and still a #2 CU GEC.
                Keep in mind 230.90 Exception No.3
                Comments based on 2017 NEC unless otherwise noted.

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