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Thread: Using a Square D QO Load Center for Combiner Box... pics and video..

  1. #1
    Join Date
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    Van Horn, TX (West TX)
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    Default Using a Square D QO Load Center for Combiner Box... pics and video..

    I did this for people who are new to solar and may be on a budget.. this case is indoor rated.. they do make a 3R rated version of this case.. wire used is 10AWG (to represent the solar panel wire) and 8AWG going to my charge controller.. The box was $20.. the outdoor box is $36 at MillsFleetFarm, HD, or Lowes..

    QO breakers are rated for up to 48 VDC.. do not however try to use this in/with a 48 VDC rated panel..

    You can use this with 12v (17vdc usually) or 24v (30 and 37vdc) panels.. again do not exceed 48VDC..

    You can series up to 2 of 12v panels (totals to 35vdc usually), or with singles of the 24vdc panels in parallel..

    Heres the basic QO612L100 box..





    Connect the backbone HOT/LOAD lugs so all the breakers will be combined.. (important to use 8AWG or heavier wire)

    I used 8AWG wire from HD (rated to about 70 amps).. I only need 60 amps..

    I went above with this 'connector' wire, some people go below with this wire..



    We will be using the built-in neutral bussbar as our NEGATIVE/GROUND bar.. Its insulated from the case and LOAD.



    At this time REMOVE the little green screw that may be installed in the neutral busbar.. that goes thru the isolation plastic and into the metal casing.. this may/may not cause a shock from the NEGATIVE side of your solar PV array.. takes about 2 turns to remove.. this screw is used for ground and neutral bonding 110V AC applications.. which were NOT doing..

    Last edited by ywhic; May 17th, 2012 at 16:49 PDT.
    Al Z.
    1160 watts PV, 30.86 & -104.792, MidNite Classic 150, Xantrex Pro SW 2000, TS 30 Transfer Switch

  2. #2
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    Default Re: Using a Square D QO Load Center for Combiner Box... pics and video..

    Bring your wires up or down (to the controller) as you want..



    Here is the positive/HOT wire coming off the COMBINER hot/load as mentioned above..
    Again use 8AWG or heavier.. (I ran out of 8AWG and used 10 for this demo)..



    Here is how the PV/Solar cable is routed.. Negative/Ground goes up to the GROUND busbar.. and the POSITIVE/HOT goes into the bottom of your QO rated breaker..



    Heres a picture of mine all labeled up with just 1 breaker.. I have my wire going OUT on the right to the charge controller.. the solar panel wires will come in on the bottom left..



    The video shows and explains the wiring as well..



    Please use strain reliefs to keep wires safe and neat..

    Al Z.
    1160 watts PV, 30.86 & -104.792, MidNite Classic 150, Xantrex Pro SW 2000, TS 30 Transfer Switch

  3. #3
    Join Date
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    pittsburgh, pa
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    Default Re: Using a Square D QO Load Center for Combiner Box... pics and video..

    very nice and good pics.

    i am wondering why you did not put in a negative bus bar to tie in all of the pv - leads? how are you handling the - leads now?
    NIEL

  4. #4
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    Default Re: Using a Square D QO Load Center for Combiner Box... pics and video..

    Quote Originally Posted by niel View Post
    very nice and good pics.

    i am wondering why you did not put in a negative bus bar to tie in all of the pv - leads? how are you handling the - leads now?
    The neutral busbar built into the box is for this purpose, is utilized as our negative bus bar..



    all the negatives from the PV/Panels will go into that and be combined.. note wires coming up from the left.. that the PV panel wires..



    Heres another shot of the insulated NEGATIVE busbar..

    Al Z.
    1160 watts PV, 30.86 & -104.792, MidNite Classic 150, Xantrex Pro SW 2000, TS 30 Transfer Switch

  5. #5
    Join Date
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    Default Re: Using a Square D QO Load Center for Combiner Box... pics and video..

    you're right and i guess i was having a senior moment. good deal.
    NIEL

  6. #6

    Default Re: Using a Square D QO Load Center for Combiner Box... pics and video..

    I did something similar, but I used a standard outdoor junction box, and noticed your standard aluminum household bus bars fit between the holes inside quite snugly.

    Name:  juncboxopen.jpg
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Size:  99.9 KB

  7. #7
    Join Date
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    Default Re: Using a Square D QO Load Center for Combiner Box... pics and video..

    Nice article w/pics. My only comment...

    Quote Originally Posted by ywhic View Post
    Connect the backbone HOT/LOAD lugs so all the breakers will be combined.. (important to use 8AWG or heavier wire)

    I used 8AWG wire from HD (rated to about 70 amps).. I only need 60 amps..
    NEC only rates 8 AWG wire w/90*C rated insulation to 55A. If you want 60A you have to go to 6 AWG (good for 75A) and 4 AWG is good for 95A. Just Google "Wire ampacity table" to confirm...

  8. #8
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    Default Re: Using a Square D QO Load Center for Combiner Box... pics and video..

    I know some may want/prefer the Midnite Solar box.. but the $$$ difference is abit steep.. IMHO..

    $9-13/breaker and the bare MNPV6 box that holds 6 is $110..

    Granted you can run 60 amp breakers up to 150VDC.. but I think some of us little folks will never see that number.. IMHO..

    Other notes..

    The 8AWG wire I have going from this combiner to my Morningstar TS-45 will be about 12"-15" in length at the max to keep loss down (0.73%)...

    I gotta stick another 60 amp breaker between this and that.. LoL.. the good news is my incoming breaker will mount on the side of the 'combiner box'..

    This combiner box will be right next to the controller and not outside.. I have 6 separate 10AWG coming to it about 12'.. (1.66% loss)

    If anyone wants to use this outdoors to combiner, and then bring it to where ever make sure you consult a wireloss guide for amperage and voltage before you run out an buy 8AWG and try going 15' with 45 amps.. you'd end up with over a 7% loss.. 6AWG would get you 4.57%, but IMHO thats still to high..
    Al Z.
    1160 watts PV, 30.86 & -104.792, MidNite Classic 150, Xantrex Pro SW 2000, TS 30 Transfer Switch

  9. #9
    Join Date
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    Default Re: Using a Square D QO Load Center for Combiner Box... pics and video..

    Quote Originally Posted by Dill View Post
    I did something similar, but I used a standard outdoor junction box, and noticed your standard aluminum household bus bars fit between the holes inside quite snugly.

    Name:  juncboxopen.jpg
Views: 2549
Size:  99.9 KB
    Wheres the fusing?? at least get some of these inline on the + side..



    or do this setup (I did this 2 weeks ago)

    Al Z.
    1160 watts PV, 30.86 & -104.792, MidNite Classic 150, Xantrex Pro SW 2000, TS 30 Transfer Switch

  10. #10

    Default Re: Using a Square D QO Load Center for Combiner Box... pics and video..

    Quote Originally Posted by ywhic View Post
    Wheres the fusing?? at least get some of these inline on the + side..


    inside down at the charge controller. 40 amp fuse (slightly over rated for my array)

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