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    #31
    Originally posted by mivey View Post
    Looks like a good illustration of why you should to me.
    Good way to waste time and money and gain nothing.
    If Billy Idol is on your playlist go reevaluate your life.

    Comment


      #32
      Originally posted by ActionDave View Post
      Good way to waste time and money and gain nothing.
      Just make sure it is someone else's money you are wasting
      I live for today, I'm just a day behind.

      Comment


        #33
        Originally posted by ActionDave View Post

        There's only one neutral to ground bond in a SDS or Non SDS.
        Incorrect.

        Originally posted by ActionDave View Post
        Fault current is moving through the system to the main source or the back up source in either case. I don't see how switching the neutral makes any difference.
        It removes a parallel path problem

        Originally posted by ActionDave View Post
        Perfect illustration why you don't need to switch the neutral.
        Are you objecting to people objecting to objectionable current or is it something else?

        Do you have some prior posts on how your particular position negates code requirements or negates the objectionable current concerns or do you feel like posting your argument here?
        BB+/BB=?

        Comment


          #34
          I finally tracked down a good graphic that illustrates the parallel path problem.
          If you bond the neutral to ground at the generator you must switch the neutral at the transfer switch, and vice versa.
          Attached Files
          The more they overthink the plumbing, the easier it is to stop up the drain

          Comment


            #35
            Originally posted by dkidd View Post
            I finally tracked down a good graphic that illustrates the parallel path problem.
            If you bond the neutral to ground at the generator you must switch the neutral at the transfer switch, and vice versa.
            Precisely. Nice pic.
            BB+/BB=?

            Comment


              #36
              edited
              Ron

              Comment


                #37
                All that graphic shows is an improper bond at the generator.
                If Billy Idol is on your playlist go reevaluate your life.

                Comment


                  #38
                  My understanding is that separately derived vs non-separately derived systems is all about the location of the grounded and grounding conductor bond point. If the two systems are bonded separately on the line side of the transfer switch then a switched-neutral is required to avoid having two bond points. If only one of the two is bonded prior to the switch then the transfer switch cannot switch the neutral and it is a non-separately derived system. If the bond is on the load side of the transfer switch, then switching the neutral will have no effect one way or the other and would not be necessary. This is also a non-separately derived system. I hope I am understanding this correctly.
                  Facilities Electrical Engineer
                  Quando Omni Flunkus Moratati

                  Comment


                    #39
                    Originally posted by ActionDave View Post
                    All that graphic shows is an improper bond at the generator.
                    It shows the improper choice of a transfer switch that doesn't switch the neutral.
                    The more they overthink the plumbing, the easier it is to stop up the drain

                    Comment


                      #40
                      Originally posted by RD35 View Post
                      My understanding is that separately derived vs non-separately derived systems is all about the location of the grounded and grounding conductor bond point. If the two systems are bonded separately on the line side of the transfer switch then a switched-neutral is required to avoid having two bond points. If only one of the two is bonded prior to the switch then the transfer switch cannot switch the neutral and it is a non-separately derived system. If the bond is on the load side of the transfer switch, then switching the neutral will have no effect one way or the other and would not be necessary. This is also a non-separately derived system. I hope I am understanding this correctly.
                      You have it right.

                      From NEC 2014

                      100 I.

                      Separately Derived System. An electrical source, other
                      than a service, having no direct connection(s) to circuit
                      conductors of any other electrical source other than those
                      established by grounding and bonding connections.


                      250.30

                      Informational Note No. 1: An alternate ac power source,
                      such as an on-site generator, is not a separately derived
                      system if the grounded conductor is solidly interconnected
                      to a service-supplied system grounded conductor. An example
                      of such a situation is where alternate source transfer
                      equipment does not include a switching action in the grounded
                      conductor and allows it to remain solidly connected to the
                      service-supplied grounded conductor when the alternate
                      source is operational and supplying the load served.

                      250.30 (A)

                      (A) Grounded Systems. A separately derived ac system
                      that is grounded shall comply with 250.30(A)(1) through
                      (A)(8). Except as otherwise permitted in this article, a
                      grounded conductor shall not be connected to normally
                      non–current-carrying metal parts of equipment, be connected
                      to equipment grounding conductors, or be reconnected
                      to ground on the load side of the system bonding
                      jumper.



                      If the neutral of a generator is solidly connected to an electrical system,
                      it is not a separately derived system.
                      The more they overthink the plumbing, the easier it is to stop up the drain

                      Comment


                        #41
                        Originally posted by dkidd View Post
                        It shows the improper choice of a transfer switch that doesn't switch the neutral.
                        It would be a lot easier to remove the bond at the generator than put in a new transfer switch.
                        If Billy Idol is on your playlist go reevaluate your life.

                        Comment


                          #42
                          I find that most transfer switch installations in our area are done incorrectly when it comes to bonding. Folks (DIY'ers...and some professionals) will install a breaker interlock and a generator feed breaker in their panel. Or, they will install a 2-pole, double throw switch. In either case, they will run a 4-wire generator feeder circuit to an L14-30 inlet where they use an extension cord to plug the transfer switch or house panel into their little 7000W portable generator. The problem lies in the fact that the generator is bonded internally. So power flows parallel through the grounded and grounding conductors of this 4-wire circuit. Funny thing is that the local inspectors and AHJ seem to be fine with it. I have considered not connecting the grounding conductor at one end or the other in order to force a fault current to travel through the neutral wire to the generator in this case. It sounds wrong to do this, but it would prevent the parallel flow problem. A 3-wire SO cord with Black, Red, White conductor colors would be even better. Any thoughts?
                          Facilities Electrical Engineer
                          Quando Omni Flunkus Moratati

                          Comment


                            #43
                            Originally posted by RD35 View Post
                            I find that most transfer switch installations in our area are done incorrectly when it comes to bonding. Folks (DIY'ers...and some professionals) will install a breaker interlock and a generator feed breaker in their panel. Or, they will install a 2-pole, double throw switch. In either case, they will run a 4-wire generator feeder circuit to an L14-30 inlet where they use an extension cord to plug the transfer switch or house panel into their little 7000W portable generator. The problem lies in the fact that the generator is bonded internally. So power flows parallel through the grounded and grounding conductors of this 4-wire circuit. Funny thing is that the local inspectors and AHJ seem to be fine with it. I have considered not connecting the grounding conductor at one end or the other in order to force a fault current to travel through the neutral wire to the generator in this case. It sounds wrong to do this, but it would prevent the parallel flow problem. A 3-wire SO cord with Black, Red, White conductor colors would be even better. Any thoughts?
                            Not all those small generators have the neutral bonded. You can set it up for what you have, then owner buys a new generator sometime down the road that is not the same, they still can plug that L14-30 cordset they already have into it though so nothing gets changed.

                            I believe NEC has made some changes and now requires some labeling, but will be read and not understood by many owners, if the L14-30 is still there they will just plug in what they have and not understand what that labeling actually means.

                            If the transfer switch is part of service equipment or is adjacent to service equipment, which seems to be fairly common in dwelling applications, the potential consequences are lessened anyway, IMO.
                            I live for today, I'm just a day behind.

                            Comment


                              #44
                              Originally posted by RD35 View Post
                              I find that most transfer switch installations in our area are done incorrectly when it comes to bonding. Folks (DIY'ers...and some professionals) will install a breaker interlock and a generator feed breaker in their panel. Or, they will install a 2-pole, double throw switch. In either case, they will run a 4-wire generator feeder circuit to an L14-30 inlet where they use an extension cord to plug the transfer switch or house panel into their little 7000W portable generator. The problem lies in the fact that the generator is bonded internally. So power flows parallel through the grounded and grounding conductors of this 4-wire circuit. Funny thing is that the local inspectors and AHJ seem to be fine with it. I have considered not connecting the grounding conductor at one end or the other in order to force a fault current to travel through the neutral wire to the generator in this case. It sounds wrong to do this, but it would prevent the parallel flow problem. A 3-wire SO cord with Black, Red, White conductor colors would be even better. Any thoughts?
                              It is almost always a rubber cord between the inlet and the generator so other than the idea that some current on the green wire it's not such a huge big deal.
                              If Billy Idol is on your playlist go reevaluate your life.

                              Comment

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