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How to calculate the right value for MCB or MMCB

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  • How to calculate the right value for MCB or MMCB

    Hi all you experienced installers.

    I hope you can help me out on this. The situation is as follows.


    The Utility connection is 23 kVA
    The Grid Tied PV System will be 20,080 Wp (78 x 260 Wp)
    Inverter 20 KW 3 phase
    The cable from Inverter to Utility distribution board is 4 x 35 mm2
    3 Phase System

    What needs to be the value of the MCB / MCCB used to connect the PV System to the grid. Please show me the calculation

    Thanks in advance, I do appreciate your answwers

    Kind regards

    Ben







    Last edited by Bendesa1962; 08-03-2018, 10:29 AM.

  • #2
    Nobody knows ? (-:

    Comment


    • #3
      You are talking several magnitudes of scale beyond what you can get for free on a internet message board. A real answer has to come from a certified engineer in the energy field.
      I can give you an answer, but if it's wrong by a factor of 20x, how would you know ?
      Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
      || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
      || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

      solar: http://tinyurl.com/LMR-Solar
      gen: http://tinyurl.com/LMR-Lister

      Comment


      • #4
        Well at least that's an answer. And what makes you think that I will take every answer here for granted? Or is it just a way of saying I don't know (-: Off course not but if people don't want to react thats fine off course. Enjoy your day.

        Comment


        • #5
          Originally posted by Bendesa1962 View Post


          Well at least that's an answer. And what makes you think that I will take every answer here for granted? Or is it just a way of saying I don't know (-: Off course not but if people don't want to react thats fine off course. Enjoy your day.

          Please show me the calculation ( from your orig 8/3 post )
          Sadly for you, I stopped showing my calculations when I graduated. So your choice is to try to bully someone to show you how to do your job, or to do your job for you.

          if you are doing a +20kw install, YOU need to know what the heck you are doing, and I cannot give you an answer, because if you withheld any info needed for a good answer and you say "Oh mike in the internet said xyz would be fine, so he's the one responsible for frying your 9 ton 3 phase transformer" well, that leaves me hanging for your job. So I CAN'T give you answer. There are many more variables you have not given us.
          Sorry I'm in a snarly mood. 2 weeks of heavy smoke, intermittent power cuts in town, worst wildfires ever in California, about 40 miles from me.

          20180729_174747.png

          Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
          || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
          || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

          solar: http://tinyurl.com/LMR-Solar
          gen: http://tinyurl.com/LMR-Lister

          Comment


          • #6
            Who said I'm going to install a 20 KW Pv System? You assumed right? He man no hard feelings. Relax and don't get so picky. I just asked the question. That's all. If you do
            n't wanna answer it. I'm fine with that. Stay save in California. I have to deal here with earth quakes....scaale 6 and 7. Take care

            Comment


            • #7
              Before anyone will give you a value for an MCB they will need to know the voltage and the short circuit interrupting rating at the connection point.

              Or we can just assume a voltage and provide you with a grossly inadequate breaker rating.

              Comment


              • #8
                Originally posted by Bendesa1962 View Post
                Who said I'm going to install a 20 KW Pv System?
                You said: "The Grid Tied PV System will be 20,080 Wp (78 x 260 Wp)." Since you're asking for advice, most people would infer from this that you are installing the 20 KW Grid Tied system. If someone else is doing the install, it wasn't obvious.
                Last edited by sdold; 08-10-2018, 12:40 PM.

                Comment


                • #9
                  Originally posted by Bendesa1962 View Post
                  Well at least that's an answer. And what makes you think that I will take every answer here for granted? Or is it just a way of saying I don't know (-: Off course not but if people don't want to react thats fine off course. Enjoy your day.
                  Dude: For someone who's looking for help, you might work on your attitude a bit. In spite of what you may think, you are not entitled to demand answers to questions you probably ought to already know.

                  Comment


                  • #10
                    Originally posted by J.P.M. View Post

                    Dude: For someone who's looking for help, you might work on your attitude a bit. In spite of what you may think, you are not entitled to demand answers to questions you probably ought to already know.
                    I don't even believe the system is in the USA. No one gives a wire size by saying 4 x 35mm2. So who knows what the 3 phase voltage is for the grid.

                    Comment


                    • #11
                      Originally posted by SunEagle View Post

                      I don't even believe the system is in the USA. No one gives a wire size by saying 4 x 35mm2. So who knows what the 3 phase voltage is for the grid.
                      I agree with your surmise, but IMO, that doesn't excuse the entitled attitude. If the OP claims expertise (?) in the engineering necessary for facilities engineering, her/his employer might like to know their hireling is asking for technical help from a chat room.

                      Comment


                      • #12
                        Well guys thank you all very much for your kind help. I do appreciate it. Thanks a lot! OMG it looks like you all are infected by your greatest president of all time Mister Trump

                        Comment


                        • #13
                          Originally posted by Bendesa1962 View Post
                          Well guys thank you all very much for your kind help. I do appreciate it. Thanks a lot! OMG it looks like you all are infected by your greatest president of all time Mister Trump
                          Actually, you are the one that is talking out of the side of your mouth. Asking many basic questions over time, bitching about answers, then adding more data to the question, and generally being an annoyance. Have a nice vacation
                          Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                          || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                          || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                          solar: http://tinyurl.com/LMR-Solar
                          gen: http://tinyurl.com/LMR-Lister

                          Comment


                          • #14
                            Originally posted by J.P.M. View Post

                            If the OP claims expertise (?) in the engineering necessary for facilities engineering, her/his employer might like to know their hireling is asking for technical help from a chat room.
                            Yeah a DIY forum made of mostly DIY non professionals. Guess who I would fire if it were my employee for being a nikenpoop?
                            Last edited by Sunking; 08-10-2018, 09:08 PM.
                            MSEE, PE

                            Comment


                            • #15
                              Originally posted by Bendesa1962 View Post
                              Well guys thank you all very much for your kind help. I do appreciate it. Thanks a lot! OMG it looks like you all are infected by your greatest president of all time Mister Trump
                              Yea. And no thanks to you for helping those sowing the seeds of divisiveness that's going to be the downfall of this once great country. You selfish, shortsighted child. Damn you.

                              Comment

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