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Grounded Conductor - Right or Wrong

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    Grounded Conductor - Right or Wrong

    Although the attached drawing is not exactly like that represented in exhibit 250.15, is it wrong? Is there any technical reason why it could not be configured as such?
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    #2
    Originally posted by MarkDavis View Post
    Although the attached drawing is not exactly like that represented in exhibit 250.15, is it wrong? Is there any technical reason why it could not be configured as such?
    Looks fine, as long as the grounding bus and conductor are sized to the greatest need. Remember to not re-bond the neutral downstream.
    Master Electrician
    Electrical Contractor
    Richmond, VA

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      #3
      I don't see something wrong, but picture has missing information/wires if you compare with exhibit 250.15 from NEC handbook 2017

      Sent from my ONEPLUS A6013 using Tapatalk

      Comment


        #4
        Many of us do not have the handbook so what is different about the graphic you've posted? This is from the 2011 NECH, not sure if it's the same as the one you're referencing. The word ground in your graphic should say SSBJ.

        Click image for larger version

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        Rob

        Moderator

        All responses based on the 2017 NEC unless otherwise noted

        Comment


          #5
          Originally posted by infinity View Post
          Many of us do not have the handbook so what is different about the graphic you've posted? This is from the 2011 NECH, not sure if it's the same as the one you're referencing. The word ground in your graphic should say SSBJ.

          [ATTACH=CONFIG]23088[/ATTACH]
          This figured changed a little bit around in the latest edition of the handbook.

          Comment


            #6
            Originally posted by MarkDavis View Post
            Although the attached drawing is not exactly like that represented in exhibit 250.15, is it wrong? Is there any technical reason why it could not be configured as such?
            Location of the "ground bus"?

            The EGC to the panelboard should be routed with the feeder conductors. If the "ground bus" is in immediate vicinity of the transformer this is less of a problem than if it is not near the transformer.
            I live for today, I'm just a day behind.

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              #7
              I have a similar question about Exhibit 250.15 in the 2017 NEC Handbook (NECH). The "Neutral" bar in the 2011 NECH Exhibit 250.13 has been changed to a "Terminal bar" in the 2017 NECH Exhibit 250.15. To me, this "Terminal bar" is the termination bar required per 450.10, which I'm guessing will be sized like a ground bus and not rated for neutral current. For example: For a K-Rated transformer with a 200% neutral, I doubt the termination bar will be rated 200% to support the neutral current. Shouldn't the neutral be connected as shown in the 2017 NECH Exhibit 250.16, such that the neutral connections are the same for either exhibit?

              Comment


                #8
                Originally posted by keefeowen View Post
                I have a similar question about Exhibit 250.15 in the 2017 NEC Handbook (NECH). The "Neutral" bar in the 2011 NECH Exhibit 250.13 has been changed to a "Terminal bar" in the 2017 NECH Exhibit 250.15. To me, this "Terminal bar" is the termination bar required per 450.10, which I'm guessing will be sized like a ground bus and not rated for neutral current. For example: For a K-Rated transformer with a 200% neutral, I doubt the termination bar will be rated 200% to support the neutral current. Shouldn't the neutral be connected as shown in the 2017 NECH Exhibit 250.16, such that the neutral connections are the same for either exhibit?
                Can you post a photo of the 2017 graphic?
                Rob

                Moderator

                All responses based on the 2017 NEC unless otherwise noted

                Comment


                  #9
                  Due to copyright restrictions, I can't. Please refer to page 184 in the 2017 NECH.

                  Comment


                    #10
                    Originally posted by keefeowen View Post
                    Due to copyright restrictions, I can't. Please refer to page 184 in the 2017 NECH.
                    Most of us do not have the 2017 NECH. It's generally accepted here that under Fair Use of copyrighted material you would be permitted to post the graphic.
                    Rob

                    Moderator

                    All responses based on the 2017 NEC unless otherwise noted

                    Comment


                      #11

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                        #12
                        Adding to my 10/22/19 question... As you can see from these two exhibits (2017 NECH Exhibit 250.15 & 250.16), the System Bonding Jumper (SBJ) in Exhibit 250.15 is now part of the neutral current return path. Thus, the SBJ and Terminal Bar would need to be sized for the neutral current. In Exhibit 250.16, the SBJ and Terminal Bar do not carry neutral neutral current. If the "white" wire in Exhibit 250.15 was moved from the Terminal Bar to the transformer X0 terminal, the SBJ and Terminal Bar would not carry neutral current and could be sized similar to Exhibit 250.16. Looking back at the 1st entry of this thread on 6/10/19, the attached file shows a similar configuration of what I think Exhibit 250.15 should be changed to show.

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                          #13
                          Just to clarify, I was calling the "black" wire between the transformer X0 and Terminal Bar in Exhibit 250.15 as the SBJ even though it's not identified as such in the exhibit. If the Terminal Bar needs to accept equipment ground conductors (EGC's), then the Terminal Bar should be treated as a ground bar and not a neutral bar.

                          Comment


                            #14
                            Originally posted by keefeowen View Post
                            Just to clarify, I was calling the "black" wire between the transformer X0 and Terminal Bar in Exhibit 250.15 as the SBJ even though it's not identified as such in the exhibit. If the Terminal Bar needs to accept equipment ground conductors (EGC's), then the Terminal Bar should be treated as a ground bar and not a neutral bar.
                            You can bond the neutral of a transformer secondary at the transformer or in the first disconnect. This has been the way this way as long as I have been alive, it is not unique to the 2017 NEC. If you bond at the first disconnect then there is no reason to separate the neutrals and equipment grounds.
                            If Billy Idol is on your playlist go reevaluate your life.

                            Comment


                              #15
                              Originally posted by keefeowen View Post
                              Adding to my 10/22/19 question... As you can see from these two exhibits (2017 NECH Exhibit 250.15 & 250.16), the System Bonding Jumper (SBJ) in Exhibit 250.15 is now part of the neutral current return path.
                              No, it's part of the fault current path.

                              Thus, the SBJ and Terminal Bar would need to be sized for the neutral current. In Exhibit 250.16, the SBJ and Terminal Bar do not carry neutral neutral current. If the "white" wire in Exhibit 250.15 was moved from the Terminal Bar to the transformer X0 terminal, the SBJ and Terminal Bar would not carry neutral current and could be sized similar to Exhibit 250.16. Looking back at the 1st entry of this thread on 6/10/19, the attached file shows a similar configuration of what I think Exhibit 250.15 should be changed to show.
                              [img] [/img]
                              If Billy Idol is on your playlist go reevaluate your life.

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