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    400 amp service

    My new home has a 400 amp service consisting of two - 200 amp panels. I have 2/O wires from the meter base to both panel lugs. The electric company came and pulled in 350 wire to the meter base. Will 350 handle my application? Thanks

    #2
    The utility always pulls in smaller conductors then the NEC requires but they have their own rules. In general they pretty well know what a customer will use so they install what will work. If it doesn't then it is their problem.
    They say I shot a man named Gray and took his wife to Italy
    She inherited a million bucks and when she died it came to me
    I can't help it if I'm lucky

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      #3
      I agree POCO can install whatever they want.

      I think the 2/0 conductors feeding each panel is not allowed.

      310.15(B)(6) allows 2/0 (copper) to be used for 200 amps.

      310.15(B)(6) however can only be used for conductors that carry the entire load of a dwelling. Since there is two feeds to the house neither one of them is carrying the entire load.
      I live for today, I'm just a day behind.

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        #4
        This is a very common way of doing a 2 panel 400. It actually provides 2 2/0 copper cables in paralell to carry the load. Too small? I think not.

        Comment


          #5
          Originally posted by kwired View Post
          I agree POCO can install whatever they want.

          I think the 2/0 conductors feeding each panel is not allowed.

          310.15(B)(6) allows 2/0 (copper) to be used for 200 amps.

          310.15(B)(6) however can only be used for conductors that carry the entire load of a dwelling. Since there is two feeds to the house neither one of them is carrying the entire load.
          Originally posted by stew View Post
          This is a very common way of doing a 2 panel 400. It actually provides 2 2/0 copper cables in parallel to carry the load. Too small? I think not.
          I find this describes a common discrepancy in this area. I feel kwired is 100% correct in that neither of those conductors carry the "full load" of the dwelling and are not parallel conductors and 2/0 should not be allowed but, locally, as Stew notes, it is accepted 99% of the time.
          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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            #6
            yes here its 99.99999 % gotta stay away from kwire if hes the inspector! lol

            Comment


              #7
              Originally posted by kwired View Post
              I agree POCO can install whatever they want.

              I think the 2/0 conductors feeding each panel is not allowed.


              310.15(B)(6) allows 2/0 (copper) to be used for 200 amps.

              310.15(B)(6) however can only be used for conductors that carry the entire load of a dwelling. Since there is two feeds to the house neither one of them is carrying the entire load.
              I agree, and this is a new home so I'm guessing that it was inspected.
              Rob

              Moderator

              All responses based on the 2017 NEC unless otherwise noted

              Comment


                #8
                Originally posted by stew View Post
                yes here its 99.99999 % gotta stay away from kwire if hes the inspector! lol
                Ditto here. IMHO and of those of local inspectors the rule does not make sense. You will hear people on this forum regurgitate the phrase diversity of loads but the truth is there are situations where it just does not make any sense.
                So if the inspectors allow it I say save your money and do it.

                Comment


                  #9
                  I believe that what you have is actually a 320 amp service, unless it is a K base(bolt in meter). Normally the bases are S base (socket base), and these are rated for 320 amps continious duty. The 350 aluminum wire the POCO used is rated at 320 amps. Actually the power company can feed that installation with #2 aluminum if the engineers believe that the #2 will carry the load. I work for a POCO and generally size 320 amp services with 4/0 aluminum if the service is short enough so as to have very little voltage drop. We actually try to account for, to a point, inrush currents causing dimming lights when AC units kick on and off.
                  One must remember that the service size is based on calculations done by the electrician. If the electrician does all his (or her) calculations, and comes up with 205 amps, guess what?, they must go to a 320 amp base.
                  If the service is unusually long, (over 250 feet) then the only reason the POCO installed the 350 was to account for voltage drop, or it was lazy engineering, and a waste of money. Must be a cooperative...

                  Comment


                    #10
                    yup If its not a ct service then it must be a 320 and yer good to go.

                    Comment


                      #11
                      Actually, that 350 wire is rated for 415 Amps, according to one manufacturer's web site.

                      Power companies can apply the manufacturer's full ratings when designing and engineering their distribution systems.

                      Comment


                        #12
                        Originally posted by stew View Post
                        yes here its 99.99999 % gotta stay away from kwire if hes the inspector! lol

                        If you didn't like a kwired "inspection" you would probably really hate mine
                        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.

                        Comment


                          #13
                          Originally posted by kbsparky View Post
                          Actually, that 350 wire is rated for 415 Amps, according to one manufacturer's web site.

                          Power companies can apply the manufacturer's full ratings when designing and engineering their distribution systems.
                          Not when we install it in conduit.

                          Comment


                            #14
                            Originally posted by stew View Post
                            yup If its not a ct service then it must be a 320 and yer good to go.

                            So you can feed a 200 amp service disconnect with #2/0's?
                            Rob

                            Moderator

                            All responses based on the 2017 NEC unless otherwise noted

                            Comment


                              #15
                              Originally posted by Twoskinsoneman View Post
                              Ditto here. IMHO and of those of local inspectors the rule does not make sense. You will hear people on this forum regurgitate the phrase diversity of loads but the truth is there are situations where it just does not make any sense.
                              So if the inspectors allow it I say save your money and do it.
                              How much do you save between 2/0 and 3/0 if you end up having to replace it? Especially if the meter is within 10 feet or so of the panels. Do it right the first time. The more of the entire service there is on a single feed the more of the possible diversity that does exist will be on that feed. Make two feeds and put mostly HVAC on one and general purpose circuits on the other and the diversity of the HVAC may not be much diversity at all. That is why the entire load of the dwelling must be supplied by the conductors to use this table.

                              Originally posted by Hv&Lv View Post
                              I believe that what you have is actually a 320 amp service, unless it is a K base(bolt in meter). Normally the bases are S base (socket base), and these are rated for 320 amps continious duty. The 350 aluminum wire the POCO used is rated at 320 amps. Actually the power company can feed that installation with #2 aluminum if the engineers believe that the #2 will carry the load. I work for a POCO and generally size 320 amp services with 4/0 aluminum if the service is short enough so as to have very little voltage drop. We actually try to account for, to a point, inrush currents causing dimming lights when AC units kick on and off.
                              One must remember that the service size is based on calculations done by the electrician. If the electrician does all his (or her) calculations, and comes up with 205 amps, guess what?, they must go to a 320 amp base.
                              If the service is unusually long, (over 250 feet) then the only reason the POCO installed the 350 was to account for voltage drop, or it was lazy engineering, and a waste of money. Must be a cooperative...
                              Since when was service size determined by what type of meter is used?

                              If you have a 320 socket supplying a 100 amp main do you have a 100 amp service or a 320 amp service?

                              If you have a 320 socket supplying two 200 amp mains will the 320 meter say "OK that is enough" if current being drawn surpasses 320, or will current be allowed to continue to rise if the demand is there until one or both of the breakers trip?
                              I live for today, I'm just a day behind.

                              Comment

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