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

ywhicywhic Posts: 612Solar Expert
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..

QOCombiner1.jpg

openbox.jpg

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..

connectLOADhots.jpg

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

insertNEGController.jpg

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..

NeutralBond.JPG
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Comments

  • ywhicywhic Posts: 612Solar Expert
    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..

    insertNEGController2.jpg

    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)..

    insertPOSController.jpg

    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..

    BreakerfromPV.jpg

    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..

    Finished.jpg

    The video shows and explains the wiring as well..

    [video=youtube_share;WzMz4k4YAVA]

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

    StrainRelief.jpg
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    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?
  • ywhicywhic Posts: 612Solar Expert
    Re: Using a Square D QO Load Center for Combiner Box... pics and video..
    niel wrote: »
    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..

    insertNEGController.jpg

    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..

    CombineWireDone.jpg

    Heres another shot of the insulated NEGATIVE busbar..

    BetterGrnd.jpg
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    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.:confused: good deal.
  • DillDill Posts: 170Solar Expert ✭✭✭✭✭
    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.

    Attachment not found.
  • dreesdrees Posts: 479Solar Expert
    Re: Using a Square D QO Load Center for Combiner Box... pics and video..

    Nice article w/pics. My only comment...
    ywhic wrote: »
    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...
  • ywhicywhic Posts: 612Solar Expert
    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..
  • ywhicywhic Posts: 612Solar Expert
    Re: Using a Square D QO Load Center for Combiner Box... pics and video..
    Dill wrote: »
    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.

    Attachment not found.

    Wheres the fusing?? at least get some of these inline on the + side..

    L46H_STD.JPG

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

    combinerbox.jpg
  • DillDill Posts: 170Solar Expert ✭✭✭✭✭
    Re: Using a Square D QO Load Center for Combiner Box... pics and video..
    ywhic wrote: »
    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)
  • ywhicywhic Posts: 612Solar Expert
    Re: Using a Square D QO Load Center for Combiner Box... pics and video..

    Is each panel fused?? or the entire set?? supposed to be 1 fuse/panel..
  • DillDill Posts: 170Solar Expert ✭✭✭✭✭
    Re: Using a Square D QO Load Center for Combiner Box... pics and video..
    ywhic wrote: »
    Is each panel fused?? or the entire set?? supposed to be 1 fuss/panel..

    the whole string is. I personally don't see the need to fuse each and every panel. If a panel shorts, my fuse at the charge controller is going to blow. In fact, I have already replaced it once, I had a couple panels sitting on my deck for testing hooked in, and the wind blew one over and shattered it. It blew the 40amp fuse. Expensive mistake :grr


    Since that picture was taken, I bought a Morningstar TriStar 60amp MPPT controller and have series wired the panels into one run, so I'm not really using the junction box for anything at this point other than to offer a connection point. This reminds me I should install a smaller fuse since the voltage is now higher, but amperage lower. Once I get some more panels I'll start using the box again...
  • CariboocootCariboocoot Posts: 17,615Banned
    Re: Using a Square D QO Load Center for Combiner Box... pics and video..

    Clarification on panel fusing: one per parallel connection (if more than one) of either single panels or a string of panels.
    If you have two strings of three panels each this counts as one parallel connection. If it is three parallel strings of two panels that is two parallel connections and each string needs separate fusing (not each individual panel).
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: Using a Square D QO Load Center for Combiner Box... pics and video..

    to clarify if you parallel more than 2 pvs or 2 strings of pvs that fusing (or circuit breakers) is not (edited to add) needed. in the case of series strings it is only the string that is fused and not each individual pv in the string. for instance, you can have 2 strings of pvs paralleled with 3 pvs in series in each string for a total of 6 pvs that no fusing is required. now if you have 3 pvs in parallel, then fusing is required on each pv output.

    darn it coot you did it again and even gave the same type example.:roll: i must be slowing way down in getting my posts up here or sometimes there's some kind of delay showing up that i didn't see your post in the thread.
  • ywhicywhic Posts: 612Solar Expert
    Re: Using a Square D QO Load Center for Combiner Box... pics and video..
    Clarification on panel fusing: one per parallel connection (if more than one) of either single panels or a string of panels.
    If you have two strings of three panels each this counts as one parallel connection. If it is three parallel strings of two panels that is two parallel connections and each string needs separate fusing (not each individual panel).

    Thanks for wording that better..

    I am doing 6 separate panels in parallel.. so I would need 6 fuses (or breakers)..

    If I decided to double my 6 panels to 12 (6 series of 2 panels) (and thereby be at 24v's) I would still utilize 6 fuse (or breakers)..

    Rest of my breakers due in tommorrow.. will put another picture up tommorrow with them all in..
  • CariboocootCariboocoot Posts: 17,615Banned
    Re: Using a Square D QO Load Center for Combiner Box... pics and video..

    Niel, it's usually my satellite connection that lags behind.
    Better take 10% off your ISP bill for their sluggish service. :p
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: Using a Square D QO Load Center for Combiner Box... pics and video..
    Niel, it's usually my satellite connection that lags behind.
    Better take 10% off your ISP bill for their sluggish service. :p

    coot,
    it's definitely not my connection so i am at a loss here for it did not take me anywhere near 8 minutes to post that.
  • CariboocootCariboocoot Posts: 17,615Banned
    Re: Using a Square D QO Load Center for Combiner Box... pics and video..
    niel wrote: »
    coot,
    it's definitely not my connection so i am at a loss here for it did not take me anywhere near 8 minutes to post that.

    So you did not send it via Canada Poste? :p

    The vagaries of the Internet!
  • bmetbmet Posts: 630Solar Expert
    Re: Using a Square D QO Load Center for Combiner Box... pics and video..
    niel wrote: »
    to clarify if you parallel more than 2 pvs or 2 strings of pvs that fusing (or circuit breakers) is not (edited to add) needed. in the case of series strings it is only the string that is fused and not each individual pv in the string. for instance, you can have 2 strings of pvs paralleled with 3 pvs in series in each string for a total of 6 pvs that no fusing is required.


    How would this work with 2 strings of 4 PVs in series?
  • CariboocootCariboocoot Posts: 17,615Banned
    Re: Using a Square D QO Load Center for Combiner Box... pics and video..
    bmet wrote: »
    How would this work with 2 strings of 4 PVs in series?

    Two strings: no fusing is required no matter how many panels are in the strings.

    When you connect panels in series the Voltage goes up but the current remains the same. Thus with two parallel panels or strings of panels one can not force greater than its Isc into the other should something go wrong. The minute you add a third you get the possibility of two of them producing maximum current to one shorted which can't take that much (2 * Isc into Isc).
  • DillDill Posts: 170Solar Expert ✭✭✭✭✭
    Re: Using a Square D QO Load Center for Combiner Box... pics and video..

    learn something new every day. I have a single, 3 panel series string currently, so I'm good just fusing the string? I'm planning on adding a 2nd, 3 panel series string in the next month or two as well. They are all 12v (17.7v) panels, so I could probably even make them a 6 panel series string as my charge controller will take up to 150V.
  • ywhicywhic Posts: 612Solar Expert
    Re: Using a Square D QO Load Center for Combiner Box... pics and video..

    NOTE:

    I just added a warning in the OP (Part #1) about removing the 110/220 neutral to ground bonding screw (green screw on neutral busbar).. with that screw into the metal case and all your pv/solar negative leads going to it you probably would get a DC negative shock.. though I am no expert..

    With the green screw removed the negative (neutral) is now truly isolated..
  • CariboocootCariboocoot Posts: 17,615Banned
    Re: Using a Square D QO Load Center for Combiner Box... pics and video..
    Dill wrote: »
    learn something new every day. I have a single, 3 panel series string currently, so I'm good just fusing the string? I'm planning on adding a 2nd, 3 panel series string in the next month or two as well. They are all 12v (17.7v) panels, so I could probably even make them a 6 panel series string as my charge controller will take up to 150V.

    You don't really need a fuse on one string or panel.
    Before you put six in series on your MPPT controller, check the Voc plus the cold temp factor. It's probably 22.1 * 6 = 132.6, plus cold temp compensation (which will vary depending on your location) up to 1.3. Where I am it wouldn't work: 172.38 certainly exceeds the 150 Volt maximum. In fact if it's more than 1.1X you're in trouble.
  • CariboocootCariboocoot Posts: 17,615Banned
    Re: Using a Square D QO Load Center for Combiner Box... pics and video..
    ywhic wrote: »
    NOTE:

    I just added a warning in the OP (Part #1) about removing the 110/220 neutral to ground bonding screw (green screw on neutral busbar).. with that screw into the metal case and all your pv/solar negative leads going to it you probably would get a DC negative shock.. though I am no expert..

    With the green screw removed the negative (neutral) is now truly isolated..

    Actually it doesn't matter much on the DC side. Usually the Voltage is low so that even if you grabbed the (+) and (-) of your panels you wouldn't feel much. Don't get your low Voltage DC in confused with the high Voltage AC out of the inverter.

    This is NOT the same as a GT array that runs hundreds of Volts: that can literally kill you.
  • DillDill Posts: 170Solar Expert ✭✭✭✭✭
    Re: Using a Square D QO Load Center for Combiner Box... pics and video..
    You don't really need a fuse on one string or panel.
    Before you put six in series on your MPPT controller, check the Voc plus the cold temp factor. It's probably 22.1 * 6 = 132.6, plus cold temp compensation (which will vary depending on your location) up to 1.3. Where I am it wouldn't work: 172.38 certainly exceeds the 150 Volt maximum. In fact if it's more than 1.1X you're in trouble.


    I'm in Minnesota, so you're right as it gets friggin cold here :) I'm probably a month away from getting the other panels anyways.

    I'm curious on the thought for fusing single, parallel panels as opposed to having a single fuse on the lead into the charge controller. If a panel shorted, wouldn't that short the entire circuit and blow the fuse (if sized appropriately)? Like I mentioned above, I had this happen to me and my fuse at the controller did indeed blow.
  • ywhicywhic Posts: 612Solar Expert
    Re: Using a Square D QO Load Center for Combiner Box... pics and video..
    Actually it doesn't matter much on the DC side. Usually the Voltage is low so that even if you grabbed the (+) and (-) of your panels you wouldn't feel much. Don't get your low Voltage DC in confused with the high Voltage AC out of the inverter.

    This is NOT the same as a GT array that runs hundreds of Volts: that can literally kill you.

    Wouldn't 17.7 VDC at 45 amps (6 panels in parallel on the combiner) hurt abit though??
  • CariboocootCariboocoot Posts: 17,615Banned
    Re: Using a Square D QO Load Center for Combiner Box... pics and video..
    ywhic wrote: »
    Wouldn't 17.7 VDC at 45 amps (6 panels in parallel on the combiner) hurt abit though??

    Without a completed circuit the current will be zero. It's that Ohm's Law thing: Amps = Voltage / Resistance. For the current to be 45 Amps @ 17.7 Volts the resistance would have to be 0.39 Ohms. That's practically a dead short.
  • CariboocootCariboocoot Posts: 17,615Banned
    Re: Using a Square D QO Load Center for Combiner Box... pics and video..
    Dill wrote: »
    I'm in Minnesota, so you're right as it gets friggin cold here :) I'm probably a month away from getting the other panels anyways.

    I'm curious on the thought for fusing single, parallel panels as opposed to having a single fuse on the lead into the charge controller. If a panel shorted, wouldn't that short the entire circuit and blow the fuse (if sized appropriately)? Like I mentioned above, I had this happen to me and my fuse at the controller did indeed blow.

    In Minn you're in the same 1.3 factor zone as me: six panels in series will not work. The Voc will be way over the limit.

    There's a difference between one string or panel shorting and one shorting when it's got two (or more) others attached to it. Panels are capable of putting out their Isc under full light and short-circuit, and that is the maximum current their construction is designed to handle. The current will always take the path of least resistance. If that path is through an adjacent panel and that panel is only capable of Isc but the source is capable of 'X' * Isc then the shorted panel can literally burst into flames.

    A short in a panel (or string) that is on its own will not blow a fuse connecting it to the charge controller because the panel will cease to output current. However, there are things that can happen to a panel that will cause it to put out more than normal current that will blow a fuse. And there are things that can happen to a charge controller that will cause a short-circuit condition or back-feed battery current to the panel. That last one is pretty much "put out the flames and replace everything".
  • ywhicywhic Posts: 612Solar Expert
    Re: Using a Square D QO Load Center for Combiner Box... pics and video..

    Thanks for the information.. though for the sake of whatever.. I'll just leave that little screw out on mine as its not needed.. LoL..

    This combiner panel will loop into a 60 amp breaker in the next day or so.. (breaker will be mounted on the outside of the same 'box' to keep everything togther on my future SOLAR wall... LoL...) then into the charge controller..

    As always thanks Cariboo for the clarification and help..
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: Using a Square D QO Load Center for Combiner Box... pics and video..
    bmet wrote: »
    How would this work with 2 strings of 4 PVs in series?

    same thing as no fusing is necessary. i was only trying to give a few examples for clarity, but i guess i needed more. it is technically the number of parallels like coot said. no fusing is required with 2 parallels or less even if each string had 10 pvs in it, but with 3 or more parallels like paralleling 3 individual pvs and then you must fuse each parallel connection.

    is this worded better that you understand?
  • westbranchwestbranch Posts: 4,144Solar Expert ✭✭✭✭
    Re: Using a Square D QO Load Center for Combiner Box... pics and video..

    Dill, when you have multiple PVs combined you want to have a separate fuse on each + line . It is there to protect each panel from being back fed by the others if a short occurs.
     
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