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  • Wire size for 240AC to load panel

    Hi, I'm a newbie here and I'm just starting a solar installation using 21 of the new Enphase micro inverters - each one will be fed by a BP175 panel. (The Enphase units convert DC to 240VAC in a small inverter right behind the panels and the AC circuits connect in series).

    My question is this. I have to install a 240VAC load panel for the power coming from the 2 240V circuits coming from the roof. The inverters wire in AC strings with a max of 15Amp capacity. So I'm running 12/3 cable to the roof from the load panel in short runs of no more than 12 feet. But I'm not sure what wire size to use for the 25+ ft. run from the load panel to the main load center. In theory it will be carrying up to 30 Amps at 240VAC, so can I use the same 12/3 BX? or do I need to go up to 10 gauge wire?

    You can read my blog about this installation at:
    http://www.arttec.net/SolarPower/index.htm

    Thanks
    Guy
    [SIZE=3][COLOR=Blue][B][URL="http://www.arttecsolar.com/"][FONT=Arial Black]ART TEC[/FONT] Solar Powered Differential Temperature Controllers[/URL][/B][/COLOR][/SIZE]

  • #2
    Guy, please call Enphase with this question. They should be able to answer your questions. You see 175 watts at 240 volts should be a small wire! Enphase has your answer.

    Comment


    • #3
      Originally posted by TekArt View Post
      Hi, I'm a newbie here and I'm just starting a solar installation using 21 of the new Enphase micro inverters - each one will be fed by a BP175 panel. (The Enphase units convert DC to 240VAC in a small inverter right behind the panels and the AC circuits connect in series).

      My question is this. I have to install a 240VAC load panel for the power coming from the 2 240V circuits coming from the roof. The inverters wire in AC strings with a max of 15Amp capacity. So I'm running 12/3 cable to the roof from the load panel in short runs of no more than 12 feet. But I'm not sure what wire size to use for the 25+ ft. run from the load panel to the main load center. In theory it will be carrying up to 30 Amps at 240VAC, so can I use the same 12/3 BX? or do I need to go up to 10 gauge wire?

      You can read my blog about this installation at:
      http://www.arttec.net/SolarPower/index.htm

      Thanks
      Guy
      My answer is the output of all inverters should be in parallel.

      And the bus wires should handle 30A~40A current. So the wire should be 10mm*mm at least.

      Comment


      • #4
        Enphase has visited to answer

        Originally posted by Off Grid Solar View Post
        Guy, please call Enphase with this question. They should be able to answer your questions. You see 175 watts at 240 volts should be a small wire! Enphase has your answer.

        Comment


        • #5
          Originally posted by TekArt View Post
          (The Enphase units convert DC to 240VAC in a small inverter right behind the panels and the AC circuits connect in series).

          In theory it will be carrying up to 30 Amps at 240VAC, so can I use the same 12/3 BX?

          or do I need to go up to 10 gauge wire?

          I'll question your "AC circuits connect in series" as that would be very strange.

          30 amps requires at least 10 gauge, and it may need to be inside conduit, where other
          standards may apply. (90C wet rated?)
          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
            series/parallel confusion

            Thanks for the thoughts. I got my terms mixed up because the Enphase inverters have 4 pin connectors that connect in series for the 240 VAC, but of course the wiring is in parallel.

            I will check with Enphase about the wire gauge. I was already planning to use flex conduit (BX) cable.

            Guy
            [SIZE=3][COLOR=Blue][B][URL="http://www.arttecsolar.com/"][FONT=Arial Black]ART TEC[/FONT] Solar Powered Differential Temperature Controllers[/URL][/B][/COLOR][/SIZE]

            Comment


            • #7
              Originally posted by TekArt View Post
              I will check with Enphase about the wire gauge. I was already planning to use flex conduit (BX) cable. Guy
              Unless you live in the town of Enphase, you should check with your local building inspecting office. They are the ones who have to sign off on your project, along with your local electric company. You generally need to submit Plans First, Construct Second, and Inspection Third. Or else risk haveing your home insurance canceled, and the city cite you for un-approved additions, and electrical service cut off.
              BX cable, in the USA, is generally only approved for short runs, and a ground (green) wire has to be pulled too. Check the spec for what type of insulation the conductors need while you are there.
              < I think BX is the flexy, spiral, armored conduit ? >
              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


              • #8
                Good advice in general principle Mike. But I don't live in an urban area, I live in rural Maine where the local town does not require permitting for solar panels so far as I know. I do plan to talk to the fire chief - who is also the code enforcement officer as a courtesy. I'll walk him through the installation to educate him about the system and what firemen may need to know about solar panels in general.
                [SIZE=3][COLOR=Blue][B][URL="http://www.arttecsolar.com/"][FONT=Arial Black]ART TEC[/FONT] Solar Powered Differential Temperature Controllers[/URL][/B][/COLOR][/SIZE]

                Comment


                • #9
                  I would not use BX. It is not water tight and will rust quickly.

                  Look at this:

                  http://www.homedepot.com/webapp/wcs/...3+90034+501108
                  Ken
                  Telford,Pa
                  Homepage: [url]http://home.comcast.net/~n3qik[/url]
                  [B]Updated 6-7-2009[/B]

                  Comment


                  • #10
                    hey Ken,

                    that link doesn't work

                    someone tried to post a home depot link in the past and it didn't work either.

                    Comment


                    • #11
                      The BX would all be inside. I will run it from the under side of a Jbox that will be screwed down to the roof and bedded in silicone. Then the BX will run a few feet over and then down to the load center.

                      I have done a lot of residential wiring before, the only reason that I posted this question was my uncertainty about wire sizing. I think I'll use 10 gauge BX (designated as 10/3).

                      Thanks for all the helpful feedback folks!
                      [SIZE=3][COLOR=Blue][B][URL="http://www.arttecsolar.com/"][FONT=Arial Black]ART TEC[/FONT] Solar Powered Differential Temperature Controllers[/URL][/B][/COLOR][/SIZE]

                      Comment


                      • #12
                        It is because of the store id.


                        Anyway, This is what I linked to:

                        AFC 1/2 In. x 100 Ft. Nonmetallic Liquid-Tight Flexible Conduit
                        Ken
                        Telford,Pa
                        Homepage: [url]http://home.comcast.net/~n3qik[/url]
                        [B]Updated 6-7-2009[/B]

                        Comment


                        • #13
                          Originally posted by TekArt View Post
                          I will run it from the under side of a Jbox
                          Most new panels do not have the Jbox. They have gone to wires with MC-4 connectors.
                          Ken
                          Telford,Pa
                          Homepage: [url]http://home.comcast.net/~n3qik[/url]
                          [B]Updated 6-7-2009[/B]

                          Comment

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