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off grid setup questions related to grounding and awg

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  • #91
    I made some changes to the drawing and believe I am getting closer. My 2 questions on the drawing are where to run the negative cables to. From the solar panel and from the charge controller.

    Outside of the solar panels and the charge controller, does the diagram / picture look correct?

    Diagram:
    elec09.jpg


    I put the questions on the drawing, but I will list them here.

    Solar Panel Negative:
    Not sure where to the negative cable from the solar panels should go. Based on previous posts it was determined that the ground should go straight to the ground rod. On the positive cable I am planning on running from the panels to the 20A breaker as a cutoff switch even if it can’t be incorporated into the dc system to use the breaker functionality. Should the negative cable go directly to the charge controller or to the dc panel busbar?

    Charge Controller Negative:
    Should the negative cable going from the charge controller to the battery also go through the DC panel busbar? On the PS-30M there is continuity between all the negative connections.




    Thanks.

    Comment


    • #92
      I do not know the right answer to your questions. The comments below are offered in the spirit of helpfulness, but please do have an electrician verify your plans before proceeding.

      If it was me doing this, I would try to minimize the number of terminations in the DC path to earth. With that in mind, I would bring the solar panel negative to the bus bar, and then run a separate negative line from the bus bar to each of the solar negative input and the battery negative input of the charge controller. Just because there is internal continuity in the charge controller, doesn't necessarily mean that conductive path is capable of carrying the full current in operation, and is why I would still make sure each current carrying conductor is wired and sized appropriately. On the bond wire between the ground bus and the electrode, be absolutely sure you are making good connections.

      Sunking offered what seems like very sound advice to me to put a battery + fuse as close as possible to the battery terminals. That doesn't appear to be in your current drawing.

      Somewhere, the AC circuit neutral need to be bonded to ground. If this were grid-tied, that would occur in the main service panel. If this is standalone, you would probably need to connect the AC neutral bus to the ground bus in your panel, or run a bond wire directly from AC neutral bus to the electrode.

      The breaker protecting the DC+ conductor for the inverter looks big. Minimum breaker size there would be 300 W / 12 V = 25 A * 1.25 = 31.25. I would probably put in a 40 A breaker.

      Edit: Never mind the comment on the breaker size. I see that it allows 600 W operation for 10 min, in which case you are looking at a 70 A breaker. With a 70 A breaker, I would increase that wire to 4 AWG.
      CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

      Comment


      • #93
        Sensij, on the AC panel. Would the bond between the neutral and the ground be through the panel? There is continuity between the neutral bar and the ground bar via the panel.


        I will also be adding in the fuses that Sunking recommended. Just forgot to put those in.


        I will make the updates to the diagram.

        Comment


        • #94
          Again, I'm offering this as an observation, please make sure to have an electrician review your system for safety and code compliance.

          Just so you understand it well, I would suggest that you see if you can find how the continuity from the neutral bar to the enclosure is being made. All of the black plastic is insulating material, and there may be a green screw or something like it making the bond from the neutral bar that results in the continuity you are measuring. Make sure that the screw is tight so the bond is solid. If the panel were to be used as an AC subpanel, that bond (screw) would need to be removed so that the neutral and ground become isolated.
          CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

          Comment


          • #95
            Originally posted by sensij View Post
            Again, I'm offering this as an observation, please make sure to have an electrician review your system for safety and code compliance.

            Just so you understand it well, I would suggest that you see if you can find how the continuity from the neutral bar to the enclosure is being made. All of the black plastic is insulating material, and there may be a green screw or something like it making the bond from the neutral bar that results in the continuity you are measuring. Make sure that the screw is tight so the bond is solid. If the panel were to be used as an AC subpanel, that bond (screw) would need to be removed so that the neutral and ground become isolated.

            Sensij, are you referring to the dc panel or the AC panel.

            The AC panel has continuity between the neutral bus and the ground bus. On the dc panel the negative and the ground wires all connect to the same busbar. Is there a good way to test the continuity or how good the connection is. I have just been using a multimeter and doing th ohms test.

            I agree with the electrician. I am still a little ways out on hooking everything up.

            Comment


            • #96
              Originally posted by arnold_ky View Post
              Sensij, are you referring to the dc panel or the AC panel.

              The AC panel has continuity between the neutral bus and the ground bus. On the dc panel the negative and the ground wires all connect to the same busbar. Is there a good way to test the continuity or how good the connection is. I have just been using a multimeter and doing th ohms test.

              I agree with the electrician. I am still a little ways out on hooking everything up.
              AC panel. The value of the electrician is not just in hooking things up, but in designing a safe system, and possibly answering your questions about why it is designed the way is, if you have a good relationship.

              Respectfully, I will no longer be contributing to this thread.
              CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

              Comment


              • #97
                Originally posted by arnold_ky View Post
                The AC panel has continuity between the neutral bus and the ground bus. On the dc panel the negative and the ground wires all connect to the same busbar. Is there a good way to test the continuity or how good the connection is. I have just been using a multimeter and doing th ohms test.

                I agree with the electrician. I am still a little ways out on hooking everything up.
                The only AC panel that should have continuity locally between the neutral bus and the EGC (Equipment Grounding Conductor = "ground") is the main service panel. Everything downstream from that, including AC combiner panels for two or more inverters, must keep the neutral bus insulated from the panel housing and from the EGC bus. This is required by the NEC and is also a very good idea.

                If you buy a panel at a big box store and the fine print somewhere on the panel says "Suitable only for use as Service Equipment", that means that there is no separate insulated neutral bus and you CANNOT use it except as your main panel.
                If is says instead "Suitable for use as Service Equipment" it will probably have two buses but they will be connected by default by a jumper wire or a green bonding screw which ties the "neutral" bus to the panel case and through that to the ground bus. You can usually convert these easily for use as a subpanel or AC combiner.
                SunnyBoy 3000 US, 18 BP Solar 175B panels.

                Comment


                • #98
                  Originally posted by inetdog View Post
                  The only AC panel that should have continuity locally between the neutral bus and the EGC (Equipment Grounding Conductor = "ground") is the main service panel. Everything downstream from that, including AC combiner panels for two or more inverters, must keep the neutral bus insulated from the panel housing and from the EGC bus. This is required by the NEC and is also a very good idea.
                  Yes. In this case, the system is fully off grid, and the panel in this design will function as the main service panel. The neutral bar and ground bar have continuity, according to the OP.
                  CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

                  Comment


                  • #99
                    Dave if you go back and look at the drawing I made for and the text, that has been covered I believe.
                    MSEE, PE

                    Comment


                    • Originally posted by Sunking View Post
                      EDIT NOTE: Ignore the Bonding Jumper between the AC Ground Bus and Neutral. It is already there and only shown to drive home that is what makes it a Ground System.
                      To be clear, in the case the ground bus and neutral bus are not bonded, a jumper between the two would serve, correct?
                      I'm working on a similar system as the OP, off-grid, will never connect to grid. After going through most of this thread, I'm not sure if it was ever made clear why (besides that it was what he had on hand) a 300w inverter (mobile) is being used. In my case, the system feeds shed lights, and the chicken coop lights and panel heater, with a total power need of less than 100w, little/no surge. I too am a noob, and have been struggling to figure the grounding part of the installation, and how to easily take power from the inverter's household grounded outlets and distribute it to the various locations. The solution was to add a breaker box and create two circuits on 15A breakers (one for the shed, one for the coop) to act as switch points, more than as circuit protection. I'll post photos if that helps. Thanks for your patience.
                      (in the interest of full disclosure, I'm also posting this question as my first post on this forum, so I'm actually allowed to see the attachments you all have posted, which I'm certain clarify what lingering questions I've got)

                      Comment


                      • Originally posted by Imwithstupid View Post
                        To be clear, in the case the ground bus and neutral bus are not bonded, a jumper between the two would serve, correct?
                        I'm working on a similar system as the OP, off-grid, will never connect to grid. After going through most of this thread, I'm not sure if it was ever made clear why (besides that it was what he had on hand) a 300w inverter (mobile) is being used. In my case, the system feeds shed lights, and the chicken coop lights and panel heater, with a total power need of less than 100w, little/no surge. I too am a noob, and have been struggling to figure the grounding part of the installation, and how to easily take power from the inverter's household grounded outlets and distribute it to the various locations. The solution was to add a breaker box and create two circuits on 15A breakers (one for the shed, one for the coop) to act as switch points, more than as circuit protection. I'll post photos if that helps. Thanks for your patience.
                        (in the interest of full disclosure, I'm also posting this question as my first post on this forum, so I'm actually allowed to see the attachments you all have posted, which I'm certain clarify what lingering questions I've got)
                        If you have a mobile Inverter, or no AC utility interconnect, and/of less than 50 volts, require NO GROUND whatsoever and would be useless. Your system is not even capable of operating 15 amp fuse or circuit breaker. Only thing you need is a 2-fuses on each of the battery term post. Observe the picture below. Ignore any green wires as it does not apply to you. Observe only the battery and fuses in the first or top drawing. Do that and you are good to go.

                        MSEE, PE

                        Comment


                        • Thanks for the quick response:
                          I opted for this inverter, on price, and relatively low power needs: http://smile.amazon.com/Go-Power-GP-...ct_top?ie=UTF8

                          The ac breaker box will just serve as a switch box for each leg, and presumably the inverter will go into overload if for some reason I run more than it can put out. Edit: Or, I can drop the box altogether, and just feed each leg by putting a plug on the end of the 12AWG wire (make them into extension cords)

                          If there is no ground at all, and I'm assuming any outlets added downstream are not grounded either. What purpose does the ground on the two outlets on the AC side of the adapter serve? This question is why I began looking into grounding and what led me to this forum. Thanks again

                          Comment


                          • Originally posted by Imwithstupid View Post
                            If there is no ground at all, and I'm assuming any outlets added downstream are not grounded either.
                            Wrong assumption. If your home was wired for AC service in the last 35 years, you outlets and AC Breaker Panel are earth grounded if code was complied with.
                            MSEE, PE

                            Comment


                            • Originally posted by Sunking View Post
                              Wrong assumption. If your home was wired for AC service in the last 35 years, you outlets and AC Breaker Panel are earth grounded if code was complied with.
                              I guess I wasn't clear in my question:
                              I wired my house, and am pretty confident in residential AC stuff, My concern is grounding in a DC to AC conversion, in the context of an off grid shed, where the power is fed by solar through an MPPT, stored in the 12V battery, and feeds the AC breaker panel through a mobile inverter, such as the one I linked, which has no ground lug on the case, but has a pair of three-hole (two slots, plus ground) outlets as the AC outputs. What purpose does the ground hole serve in these outlets? If one added a plug to a 12-2 to feed the breaker panel (with separate neutral and ground Bus, and jumpers between the two hot lugs, as the OP showed initially), and outlets are added to each branch from there, I'm not seeing how anything downstream is grounded, despite the ground hole in the outlet on the inverter.

                              Hope that clarifies the question, thanks again.outlet.jpg
                              Last edited by Imwithstupid; 11-22-2015, 09:50 AM. Reason: added photo of the inverter outlet

                              Comment


                              • NO GROUND REQUIRED. Your Inverteer uses GFCI which REQUIRES NO GROUND.
                                MSEE, PE

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