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    #31
    Originally posted by mopowr steve View Post
    It was actually for a concession trailer where-as the onboard generator has the neutral and equipment ground tied together (as should be) but when it came to plugging in to shore power the equipment ground and neutral need to be isolated (otherwise if plugged into GFCI circuit it would trip, because of the neutral/equip gnd tied together at generator.)
    That I can understand. Can you explain how the "automatic ground bonding relay" works and what makes it different from a transfer switch.

    --
    Tom Horne
    Tom Horne

    "This alternating current stuff is just a fad. It is much too dangerous for general use." Thomas Alva Edison

    Comment


      #32
      It only breaks the bond between neutral and equipment ground when the generator is not running, there-fore making the panel “ready for shore power connection”. This is utilized when there is a manual transfer interlock used instead of an ATS.

      Comment


        #33
        well this is interesting...so where would the MBJ exist? On the camper, or within the external supply to it? ~RJ~

        Comment


          #34
          Originally posted by romex jockey View Post
          well this is interesting...so where would the MBJ exist? On the camper, or within the external supply to it? ~RJ~
          A basic principle of Safety Engineering is that it should take 2 failures of the system that is being designed to subject people to the risk of injury.

          If I am understanding what mopowr steve is saying this bonding relay is the answer to having a Main Bonding Jumper in 2 different and mutually incompatible places. There is a Main Bonding Jumper at the park Service Equipment Enclosure. There is also a Main Bonding Jumper between the Neutral Point of the RV's Generator windings and the frame of the Generator. Since that frame is Bonded to the frame of the vehicle, when the generator is mounted on the vehicle, there is a deliberate connection between the generator winding's neutral point and the conductive parts of the vehicle frame. That connection must be opened when the RV is operating on park power because any connection between the Grounded Current Carrying Conductor ("NEUTRAL") and ground on the load side of the parks wiring system Service Disconnecting Means can provide a leakage pathway for the neutral current to flow on the exposed conductive parts of the parks wiring system and, more importantly for your purposes, on the exposed conductive parts of the RV. If the second failure were also present and the neutral conductor were to have an open or high impedance connection most of the neutral current would travel on those surfaces to return to the park's Service Equipment and thus to the power utility's transformer secondary from whence it came. Since every foot of conductor takes some voltage to move the current through it the total voltage used up in that way is called voltage drop. With the neutral intact and insulated from ground the voltage drop on the neutral conductor does not have any deleterious effect. But if the neutral current were to flow over the unintended pathways of the metal parts of the electrical system the resultant voltage difference between the frame of the RV and the earth beneath it will create what is called a touch potential that could give you a shock when you went to open the door from the outside of the RV. The relay that mopowr steve is talking about brakes the connection between the generator winding and the generator frame whenever the generator stops running.

          I have some reservations about using a separate device to do this because it would need to be carefully interlocked to the transfer mechanism so that the shore power will not connect if it does not break the connection. Best practice is to have that disconnection made by the same device which connects the shore power.

          --
          Tom Horne
          Last edited by hornetd; 08-15-19, 11:03 AM. Reason: Add Signature
          Tom Horne

          "This alternating current stuff is just a fad. It is much too dangerous for general use." Thomas Alva Edison

          Comment


            #35
            Originally posted by hornetd View Post
            ...In a completely off the subject side note has anyone had to convince a project manager that when it says optional in the catalog it means One or the Other rather than not needed. It is like pulling teeth as the old saying goes.
            Doesn't "optional" mean Not Required At All, but you may include this if you really want to?? Oh, and if you really want to, here are the things you can select. Do you want the standard cloth seats, or one of these 'optional' seat covers: Leather, Dragon Hide, Ostrich Hide? Otherwise shown as "available leather seats" in the ads.

            Comment


              #36
              Originally posted by PaulMmn View Post

              Doesn't "optional" mean Not Required At All, but you may include this if you really want to?? Oh, and if you really want to, here are the things you can select. Do you want the standard cloth seats, or one of these 'optional' seat covers: Leather, Dragon Hide, Ostrich Hide? Otherwise shown as "available leather seats" in the ads.
              You should begin your new career as a project manager at once. Your a natural. In electrical work an option is a choice as in you have 2 options here. An extra is something you can take or leave.

              --
              Tom Horne
              Tom Horne

              "This alternating current stuff is just a fad. It is much too dangerous for general use." Thomas Alva Edison

              Comment


                #37
                Originally posted by hornetd View Post
                You should begin your new career as a project manager at once. Your a natural. In electrical work an option is a choice as in you have 2 options here. An extra is something you can take or leave.
                --
                Tom Horne
                Ah! It's not "optional," it's "Options." A difference in meaning with a change of a few letters!

                Or, the catalog lists the standard features, then says, "Optional-- fuse box instead of switch box." Or does the catalog assume you know what the optional item will be instead of?

                Comment


                  #38
                  Originally posted by PaulMmn View Post

                  Ah! It's not "optional," it's "Options." A difference in meaning with a change of a few letters!

                  Or, the catalog lists the standard features, then says, "Optional-- fuse box instead of switch box." Or does the catalog assume you know what the optional item will be instead of?
                  The people who write the catalog language are under the mistaken belief that the catalog will be used by someone who knows which end of the windings gets connected to what part of the building wiring. They seem to have failed to anticipate that the catalog would be used by people who were trained in the Andrew Carnegie school of business. "If you take care of costs profit takes care of itself." That is why so many of the conversations with project "managers" end with the installation foreman screaming "Have you ever done electrical work! What was it like!"

                  --

                  Tom Horne
                  Tom Horne

                  "This alternating current stuff is just a fad. It is much too dangerous for general use." Thomas Alva Edison

                  Comment


                    #39
                    Originally posted by hbiss View Post
                    ... To tell you the truth, even towing that at highway speeds with a 1 ton pickup scares me. And touring America? ...
                    I'm not getting your meaning. Scared of what? That cargo hauler was designed to load up to maybe 12,000 lbs, connect to a suitable towing capacity vehicle, using a suitable rated hitch, and drive anywhere the pickup can drag it.

                    Got to go - I'm dragging my 7500 lb toy hauler, using my pussycat F150, about 1000 Miles across CONUS interior this next week.

                    the worm
                    Without data you’re just another person with an opinion – Edwards Deming

                    Comment


                      #40
                      Originally posted by mopowr steve View Post
                      It was actually for a concession trailer where-as the onboard generator has the neutral and equipment ground tied together (as should be) but when it came to plugging in to shore power the equipment ground and neutral need to be isolated (otherwise if plugged into GFCI circuit it would trip, because of the neutral/equip gnd tied together at generator.)
                      Most standard shore power receptacles for RV"s are 30 amp 125v or 120/240v 50 amp non-gfi protected outlets, unless your under the new code requirements.

                      If an ATS was not in play, and you simply unplugged one of these cords (That fed the panel in the concession stand) from the generator and plugged it into one of these standard non-gfi protected receptacles, they would not trip.

                      Since your indicating that when plugging into shore power it would "Trip the GFI", then, I'm assuming your talking about plugging the feeder cable to the concession stand into a "Shore Power" 120v GFI protected outlet, or, using some type of 30a 125v or 50a 125/240v adapter to be able do so.



                      JAP>

                      Comment


                        #41
                        Originally posted by jap View Post

                        Most standard shore power receptacles for RV"s are 30 amp 125v or 120/240v 50 amp non-gfi protected outlets, unless your under the new code requirements.

                        If an ATS was not in play, and you simply unplugged one of these cords (That fed the panel in the concession stand) from the generator and plugged it into one of these standard non-gfi protected receptacles, they would not trip.

                        Since your indicating that when plugging into shore power it would "Trip the GFI", then, I'm assuming your talking about plugging the feeder cable to the concession stand into a "Shore Power" 120v GFI protected outlet, or, using some type of 30a 125v or 50a 125/240v adapter to be able do so.



                        JAP>
                        Regardless if there is gfi protection of a receptacle that this would plug into, it is still a mobile piece of equipment that contains a sub-panel and there-fore the neutral and grounds need to be separated unless the power being supplied is provided onboard.

                        Comment


                          #42
                          Originally posted by mopowr steve View Post

                          Regardless if there is gfi protection of a receptacle that this would plug into, it is still a mobile piece of equipment that contains a sub-panel and there-fore the neutral and grounds need to be separated unless the power being supplied is provided onboard.

                          He did indicate there was onboard power being supplied through a generator where the Neutral and Ground was tied together.

                          Hence his trouble of tripping the shore power GFI without the proper transfer device.

                          JAP>

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