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  • Best Wiring Practices

    So far I have the PV array installed, the combiner box installed, and the CC mounted. I have already wired and tested the PV array circuits to in the combiner box and they are attached to DC circuit breakers. So far so good.

    From the positive bus bar in the combiner I will loop into a Ground Fault circuit breaker inside the combiner box and then out to the CC array positive in. From the negative combiner bus bar it will connect to the CC array negative in.

    The CC also has a positive and negative connection for the battery bank which seems straight forward if all I was going to do is connect a battery.

    Between the Battery and the CC, however, I will be connecting a 48v inverter, and possibly tying in a Anderson Power Pole fused distribution strip in case I want to make direct 48v DC connections to the battery bank.

    I know I need to fuse the positive lead off the battery bank and want to be able to disconnect the CC from anything on the load side so I can isolate it when needed. The array side of the CC, as mentioned above, already has breakers to isolate it on that side.

    What is the best practice to connect these components on the battery side of the CC? Positive and negative bus bars? fused bus bar? Another circuit breaker box using that bus bar to make the connections? Or something totally different? Should I put a fuse/breaker next to the battery and also next to the CC with the inverter some how tied in the middle?

    Any suggestions are welcome.

    Thanks

  • #2
    Originally posted by johngalt View Post
    The CC also has a positive and negative connection for the battery bank which seems straight forward if all I was going to do is connect a battery.

    Between the Battery and the CC, however, I will be connecting a 48v inverter, and possibly tying in a Anderson Power Pole fused distribution strip in case I want to make direct 48v DC connections to the battery bank.

    I know I need to fuse the positive lead off the battery bank and want to be able to disconnect the CC from anything on the load side so I can isolate it when needed. The array side of the CC, as mentioned above, already has breakers to isolate it on that side.

    What is the best practice to connect these components on the battery side of the CC? Positive and negative bus bars? fused bus bar? Another circuit breaker box using that bus bar to make the connections? Or something totally different? Should I put a fuse/breaker next to the battery and also next to the CC with the inverter some how tied in the middle?

    Any suggestions are welcome.

    Thanks
    Is this going to be a grounded system, or Floating> If floating you need to fuse both polarities.
    MSEE, PE

    Comment


    • #3
      Originally posted by Sunking View Post
      Is this going to be a grounded system, or Floating> If floating you need to fuse both polarities.
      Grounded. I have a 6 AWG stranded ground wire running from the house ground which is copper ground rod just outside the foundation to a ground bar mounted on the backboard where all other components are being mounted. I have already grounded the combiner box to the ground bar and will do the same for the CC and inverter.

      I this what you mean?

      Comment


      • #4
        Grounded System does not mean the chassis or metallic parts you can touch. That is always required.

        Grounded System means one of the circuit conductors is reference to something like earth or a body in place of earth like a chassis.
        MSEE, PE

        Comment


        • #5
          Originally posted by Sunking View Post
          Grounded System does not mean the chassis or metallic parts you can touch. That is always required.

          Grounded System means one of the circuit conductors is reference to something like earth or a body in place of earth like a chassis.
          OK, like the picture below? This is not the controller I am using but it does show the negative side of the battery going to earth ground.

          Can this connection go to the same ground rod as the chassis grounding or does it have to be separate?

          This also adds to my original question; what is the best way to make all these connections come together? I guess from the negative battery side I could have a common bus bar for all the negatives and then take it to ground from there.

          The combiner side was easy with multiple connections going in and only one positive and negative coming out. Now from the CC I have one negative and positive coming out but need to make multiple connections. I've seen a couple examples on the Internet. Some looked OK, others looked like a disaster waiting to happen.

          Comment


          • #6
            Have any of you used a breaker like this for the battery instead of a fuse? I like the idea of being able to reset it vs. replace it.

            Comment


            • #7
              Originally posted by johngalt View Post
              Have any of you used a breaker like this for the battery instead of a fuse? I like the idea of being able to reset it vs. replace it.
              Looking only at the page you copied, it is not obvious what voltage rating these circuit breakers are designed for. In a DC circuit, opening under load is a lot more difficult than in a AC circuit because the current does not pass through zero 120 time per second and safely extinguishing an arc becomes an issue.
              In this case the more detailed specs on page 6 here seem to indicate that they would be OK in a nominal 48 volt system, but it might be pushing it since the actual voltage would be higher than the nominal voltage. I would check with the manufacturer for confirmation.
              SunnyBoy 3000 US, 18 BP Solar 175B panels.

              Comment


              • #8
                I am not going to comment much about Grounding because it is too complicated for DIY and I will not be held responsible. What I will tell you is Fuses Blow and Breakers Suck when it comes to DC.
                MSEE, PE

                Comment


                • #9
                  Originally posted by Sunking View Post
                  I am not going to comment much about Grounding because it is too complicated for DIY and I will not be held responsible. What I will tell you is Fuses Blow and Breakers Suck when it comes to DC.
                  I understand.

                  If I continue to post you'll know I got it right. If not, it was nice talking to you guys.

                  Thanks

                  Comment


                  • #10
                    Originally posted by johngalt View Post
                    Have any of you used a breaker like this for the battery instead of a fuse? I like the idea of being able to reset it vs. replace it.
                    I use one similar to this (made by Blue Sea) for a battery disconnect switch but still use smaller fuses in a distribution block for proper fusing. Has worked fine in my small system for a few months now resetting my Turnigy power analyzer every morning.

                    Blue Sea's specs;

                    Maximum Voltage Rating 48 Volts DC
                    Operating Temperature Range -40C to 85C
                    Circuit Breaker Type Thermally Responsive bi-metal blade
                    Circuit Breaker Class Type III - Switchable / Manual Reset - Trip Free
                    Terminal Stud Size M6 (accepts 1/4″ Ring Terminal)

                    Comment


                    • #11
                      Originally posted by Sunking View Post
                      I am not going to comment much about Grounding because it is too complicated for DIY and I will not be held responsible. What I will tell you is Fuses Blow and Breakers Suck when it comes to DC.

                      Howsabout giving him that link to John Wiles' SAND 2005-0342-N paper. Forget which post you had that in but reading that really helped me. Thanks!

                      Comment


                      • #12
                        Originally posted by FloridaSun View Post
                        I use one similar to this (made by Blue Sea) for a battery disconnect switch but still use smaller fuses in a distribution block for proper fusing. Has worked fine in my small system for a few months now resetting my Turnigy power analyzer every morning.

                        Blue Sea's specs;

                        Maximum Voltage Rating 48 Volts DC
                        Operating Temperature Range -40C to 85C
                        Circuit Breaker Type Thermally Responsive bi-metal blade
                        Circuit Breaker Class Type III - Switchable / Manual Reset - Trip Free
                        Terminal Stud Size M6 (accepts 1/4″ Ring Terminal)
                        Thanks - I've decided nothing at this point. Still trying to visualize what I need to accomplish.

                        I just found this diagram which is very similar to my setup. I just have to decide the best way to connect the components and fuse/breaker where necessary along with the correct sizing for each connection.

                        I will NOT be grounding the battery system. I read too many negatives about what can happen with an inverter and grounded batteries. I will instead ground the combiner box, CC, and Inverter where indicated and install the ground fault breaker in the combiner box to automatically cut power from the array should a fault condition occur. I have already grounded the panel frames to their mounting brackets and the mounting brackets to an 8' copper ground rod. That's about as far as I'm going to take the grounding situation for now.

                        Comment


                        • #13
                          Originally posted by FloridaSun View Post
                          Howsabout giving him that link to John Wiles' SAND 2005-0342-N paper. Forget which post you had that in but reading that really helped me. Thanks!
                          Is this the document you are referring to?

                          http://www.contractorsinstitute.com/...hn%20Wiles.pdf

                          Comment


                          • #14
                            Originally posted by johngalt View Post
                            Is this the document you are referring to?

                            http://www.contractorsinstitute.com/...hn%20Wiles.pdf
                            yuppers, that's the one

                            Comment


                            • #15
                              Originally posted by FloridaSun View Post
                              yuppers, that's the one

                              Thanks.

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