dc breaker question

cizzicizzi Solar Expert Posts: 109 ✭✭✭✭
For my 12 volt solar system would a

"Midnite Solar 15 amp 150 VDC din rail mounted breaker"

be good? few reasons I ask.. it says "150 VDC".. second of all i never seen one of these close.. how do they go connected? with AC breakers you connect them in the bus bar (snap or screw) and connect the black in the screw..

but im looking to buy a small midnight solar baby dc box ( http://www.theresourcestore.ca/proddetail.php?prod=MN-BB ) without any bus bar as far as I can tell, how do the wires connect to the breakers? is there 2 screws? one for the postive and one for the negative? thanks

Comments

  • Solar GuppySolar Guppy Solar Expert Posts: 1,962 ✭✭✭
    Re: dc breaker question

    For 12VDC, go to home depot and get an AC disconnect box ( like 15 dollars ) and then get some Square-D QO 15 amp breakers which are DC rated to 50VDC
  • BB.BB. Super Moderators, Administrators Posts: 30,522 admin
    Re: dc breaker question

    Cizzi,

    You don't need to open a new thread for each question you have... Since this is all about your one system, there will be less confusion if we keep the discussions (and answers) all on one thread.

    Or you end up with the same question asked/answered like this one on breakers in several threads.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • JESSICAJESSICA Solar Expert Posts: 289 ✭✭
    Re: dc breaker question

    Cizzi:

    The Square D QOU 15 amp DC circuit breaker can be mounted even without the box or enclosure.

    Best price here: http://store.solar-electric.com/squardqou15a.html
  • cizzicizzi Solar Expert Posts: 109 ✭✭✭✭
    Re: dc breaker question

    My local home depot would have this:

    http://www.homedepot.ca/webapp/wcs/stores/servlet/CatalogSearchResultView?D=901398&Ntt=901398&catalogId=10051&langId=-15&storeId=10051&Dx=mode+matchallpartial&Ntx=mode+matchall&recN=0&N=0&Ntk=P_PartNumber

    Which is a square D QO 15 amp breaker however in the description and specs it does not mention DC.. is this the same breaker you folks are talking about?
  • n3qikn3qik Solar Expert Posts: 741 ✭✭
    Re: dc breaker question

    Yes, that is the type you want. I have two of the QO distribution panels with 12 of the QO breakers.

    The QO line is UL rated to 48VDC at 5000 AIR.

    Here is link to the PDF file:
    http://ecatalog.squared.com/techlib/displaydocument.cfm?id=0730CT9801&action=view

    Goto page 5
  • cizzicizzi Solar Expert Posts: 109 ✭✭✭✭
    Re: dc breaker question

    its just that the breaker in that link doesnt look like the one someone else posted here: http://store.solar-electric.com/squardqou15a.html
  • cizzicizzi Solar Expert Posts: 109 ✭✭✭✭
    Re: dc breaker question

    allright I know how to wire an AC panel, as far as DC.. what are the basic rules? would I only use 1 line with my hot live wire and use the white bus bar for my black (negative) and then clicp in my breaker?
  • BB.BB. Super Moderators, Administrators Posts: 30,522 admin
    Re: dc breaker question

    Wiring is pretty much common sense... Wire the + through the breaker to your load. The return back to the Neutral bus bar... Don't tie "neutral/negative" bus bar to ground except in one location--typically where the earth ground wire enters near the ground rod.

    Also, remember that this is not a center tap transformer (120/240 VAC) system... So that the "neutral" from an "A" and "B" phase of a 120/240 VAC do not cancel in a DC circuit--they add.

    Wiring colors--If you will ever wire this for 120 VAC--then follow AC wiring colors/practices... And use a wrap of color tape on each end of the run to identify +/- leads (red=+? black=+? white=-? grn=-? etc.).

    If you are using automotive type electronics--typically the car chassis is "GROUND"... In your wiring here, you will find that "-" is not the same as "earth gnd/grn"... So, when wiring a car type radios/cb/ham/etc... You may end up with issues where earth and "-" ground can case a volt or so difference with the chassis/antenna grounds, etc. Think how you want things wired, and make sure you avoid having currents share return paths, or issues where two cases touch and you get a (typically small) arc.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • cizzicizzi Solar Expert Posts: 109 ✭✭✭✭
    Re: dc breaker question

    thanks bb.. also found this diagram which simplifies things for me as well..

    http://www.newmarpower.com/Electrical_Panels/Accessory_Panel_Wiring2.jpg
  • cizzicizzi Solar Expert Posts: 109 ✭✭✭✭
    Re: dc breaker question

    also since i'm using just 1 line of the bus bar (1 phase) I would only connect my breakers on the rows which use that bus bar right? skipping one.. makes sense?
  • BB.BB. Super Moderators, Administrators Posts: 30,522 admin
    Re: dc breaker question

    You can also just "bus" the A and B bus bars together... And both will be a "+" connection.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Solar GuppySolar Guppy Solar Expert Posts: 1,962 ✭✭✭
    Re: dc breaker question

    That Diagram has the + and - reversed on the load side. If you look closely, it shows the + coming from the common - bond, not the breaker
  • cizzicizzi Solar Expert Posts: 109 ✭✭✭✭
    Re: dc breaker question

    thanks for pointing that out.. thought it was weird too.. since you dont want to put a + and - on the same bus bar
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