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    #31
    Originally posted by Wire-Smith View Post
    i didn't say it required it, just that i would do it.

    although i believe it is required in patient care areas if that happens to be the location.
    Its not patient care areas or healthcare. Its warehouse with office. Service equipment enclosure are typically bonded to the gnd bus, neutral bus with main bonding jumper. So swbd #1 and swbd #2 enclosure would be bonded together via common busbar, GEC system attached sketch post #29.
    Last edited by hhsting; 01-25-19, 10:31 PM.

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      #32
      Originally posted by Wire-Smith View Post
      wait until one of these days you run across a building with a double bond and you lose one of the service neutrals, you'll see things like flex sparking against conduits, pipes. and it could also happen without losing a neutral but would likely not cause a problem unless you have decent neutral current, but then again it doesn't take much current to do a lot of damage under the right circumstances. i have heard of people feeling circulating ground current in the shower (albeit metal plumbing, but you get the hint).
      What do you do when the fire pump service is required to be remote from other service disconnects?


      I still do not see what you are pointing to as a code violation, what if one service was single phase and one service three phase taken from the same three phase utility bank, happens a lot around here.

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        #33
        Originally posted by david View Post
        What do you do when the fire pump service is required to be remote from other service disconnects?
        i can't think of a scenario where you can't get rid of objectionable current, if you would like to expand on what you are describing i would appreciate it. sometimes the easiest way is to add an additional transformer at the premises for the "normal electrical system", sometimes it's easier to add disconnects to where all the main bonds are grouped.


        Originally posted by david View Post
        I still do not see what you are pointing to as a code violation, what if one service was single phase and one service three phase taken from the same three phase utility bank, happens a lot around here.

        this is what i see as the likely code violation
        250.6 Objectionable Current. (A) Arrangement to Prevent Objectionable Current. The grounding of electrical systems, circuit conductors, surge arresters, surge-protective devices, and conductive normally non–current-carrying metal parts of equipment shall be installed and arranged in a manner that will prevent objectionable current
        in the O.P.s scenario with two main bonds in different areas(not very close to each-other) served by the same transformer you would have neutral current on your grounded equipment if you have any neutral load, your grounded equipment is a parallel neutral path.

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          #34
          Originally posted by Wire-Smith View Post
          i can't think of a scenario where you can't get rid of objectionable current, if you would like to expand on what you are describing i would appreciate it. sometimes the easiest way is to add an additional transformer at the premises for the "normal electrical system", sometimes it's easier to add disconnects to where all the main bonds are grouped.





          this is what i see as the likely code violation


          in the O.P.s scenario with two main bonds in different areas(not very close to each-other) served by the same transformer you would have neutral current on your grounded equipment if you have any neutral load, your grounded equipment is a parallel neutral path.
          Utility in our area will only serve with one transformer not two. What do you mean by disconnects where main bonding jumpers are grouped?

          Sent from my SM-G935U using Tapatalk

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            #35
            Originally posted by Wire-Smith View Post
            i can't think of a scenario where you can't get rid of objectionable current, if you would like to expand on what you are describing i would appreciate it. sometimes the easiest way is to add an additional transformer at the premises for the "normal electrical system", sometimes it's easier to add disconnects to where all the main bonds are grouped.





            this is what i see as the likely code violation


            in the O.P.s scenario with two main bonds in different areas(not very close to each-other) served by the same transformer you would have neutral current on your grounded equipment if you have any neutral load, your grounded equipment is a parallel neutral path.
            Even when service discos grouped you have parallel paths. Resistance of cable would be almost same so current divide between two paths but paths are still there.

            Sent from my SM-G935U using Tapatalk

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              #36
              Originally posted by hhsting View Post
              Utility in our area will only serve with one transformer not two. What do you mean by disconnects where main bonding jumpers are grouped?

              Sent from my SM-G935U using Tapatalk
              The additional transformer would be on the premises side of the service, so you can do your main bond for that system at and only at the transformer.

              I mean having the main disconnects grouped where the only main bonds on the premises are. You would still technically have circulating ground current because of two bonds, but it would arguably and likely not be objectionable current because they are physically located and connected so closely together. Its like on commercial buildings with multiple units and you have multiple main disconnects grouped together with multiple main bonds, although you could do it a better way I don't see a likely problem since they are grouped.

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                #37
                Originally posted by hhsting View Post
                Even when service discos grouped you have parallel paths. Resistance of cable would be almost same so current divide between two paths but paths are still there.

                Sent from my SM-G935U using Tapatalk
                My concern is not the neutral current dividing among the two service neutrals, it would do that.

                My concern is the bonded and grounded equipment, like conduits, grounding electrode conductors, equipment grounding conductors, these would be carrying neutral current if two main bonds from one transformer are located in different areas and bonded by things such as building steel, grounds, pipes, reinforced concrete, etc, or a combination of them

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                  #38
                  Originally posted by Wire-Smith View Post
                  My concern is not the neutral current dividing among the two service neutrals, it would do that.

                  My concern is the bonded and grounded equipment, like conduits, grounding electrode conductors, equipment grounding conductors, these would be carrying neutral current if two main bonds from one transformer are located in different areas and bonded by things such as building steel, grounds, pipes, reinforced concrete, etc, or a combination of them
                  I meant that what you are saying is neutral current going to GEC, GE it would still do that even if service disconnects are grouped closely. The neutral parallel path would still be there.

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                    #39
                    Originally posted by Wire-Smith View Post
                    The additional transformer would be on the premises side of the service, so you can do your main bond for that system at and only at the transformer.

                    I mean having the main disconnects grouped where the only main bonds on the premises are. You would still technically have circulating ground current because of two bonds, but it would arguably and likely not be objectionable current because they are physically located and connected so closely together. Its like on commercial buildings with multiple units and you have multiple main disconnects grouped together with multiple main bonds, although you could do it a better way I don't see a likely problem since they are grouped.
                    I think utility around here do give another transformer if for fire pump and thats my case.

                    So what if you have two separate utiltiy transformers? Would this still happen?

                    Sent from my SM-G935U using Tapatalk

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                      #40
                      Originally posted by hhsting View Post
                      I meant that what you are saying is neutral current going to GEC, GE it would still do that even if service disconnects are grouped closely. The neutral parallel path would still be there.
                      Correct it would, but since they are so closely grouped it's not much different then say you have a parallel feed(not talking about your scenario, one service but parallel wires for ampacity. So say you have two parallel service neutrals going to one main switchboard or whatever, and the neutrals land on the neutral bar, say it's a decent size piece of equipment and the neutrals are a foot apart on the neutral bar, and it's old school and both mounting bolts bond it to enclosure. Do you think much neutral current is going to be on the related grounded and bonded non current carrying equipment? It would be negligible if anything, that is effectively the same thing you are doing with keeping them close together and bonding the enclosures right there close to the main bonds. Current discriminates, it will take all paths but disproportionately relative to impedance, shorter path=lower impedance.

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                        #41
                        Originally posted by hhsting View Post
                        I think utility around here do give another transformer if for fire pump and thats my case.

                        So what if you have two separate utiltiy transformers? Would this still happen?

                        Sent from my SM-G935U using Tapatalk
                        Yes, because utility secondary is likely grounded to the multipoint grounded utility neutral and then you are likely going to bond again at premises.
                        Not a concern to me if main bonds are physically close with a good local bond between them, or you use a premises isolation transformer on any of the services with neutral loads, before any neutral load on the system. And bond that isolation transformer secondary only at the transformer.
                        Last edited by Wire-Smith; 01-26-19, 09:41 AM.

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                          #42
                          Originally posted by Wire-Smith View Post
                          Yes, because utility secondary is likely grounded to the multipoint grounded utility neutral and then you are likely going to bond again at premises.
                          Not a concern to me if main bonds are physically close with a good local bond between them, or you use a premises isolation transformer on any of the services with neutral loads, before any neutral load on the system. And bond that isolation transformer secondary only at the transformer.
                          Edit
                          Change last sentence to " only at one location."
                          Last edited by Wire-Smith; 01-26-19, 09:49 AM.

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                            #43
                            Originally posted by Wire-Smith View Post
                            Edit
                            Change last sentence to " only at one location."
                            Ok what about I have something like the attached sketch? Top is exterior view bottom is actual wiring of two service disconnects. It has local bond and swbd as close as possible.

                            Sent from my SM-G935U using Tapatalk

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                              #44
                              Originally posted by hhsting View Post
                              Ok what about I have something like the attached sketch? Top is exterior view bottom is actual wiring of two service disconnects. It has local bond and swbd as close as possible.

                              Sent from my SM-G935U using Tapatalk
                              Looks good to me, I obviously don't know how far apart the panels are or what non current carrying metal equipment is in between them, but if they are close there would likely be no problems and therefore arguably no code violation

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                                #45
                                About GEC though, I should add SWB2 GEC should be as short as practical to the actual grounding electrode system

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