"quick" wiring question...

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couchsachraga
couchsachraga Solar Expert Posts: 84 ✭✭
in Off Grid Solar & Battery Systems #1
I"m in the midst of upgrading my occasional use off-grid system (going from 6 ancient (70's) 30w each panels to 4 Solar World 270w panels, as well as increasing my battery bank (now 4 Trojan T1275's (600Ah total, 12v).). As the vast majority of the system is 12v I do not have a big inverter (just a Suresine for occasional use), so no big breaker / inverter disconnect box. BUT, I still want to have the batteries have a disconnect / fuse/ breaker of some sort.

Any reason NOT to use one of these?

http://www.amazon.com/gp/product/B0051P01BW/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=A1UNWS4MSNTF2A

(Blue Sea 285 series 100 amp DC breaker)

100 amps is WAY more than my system draws obviously, though I'm not sure exactly what the maximum amps my Midnite Classic 200 will be putting IN to the batteries either (maximum output is 79 amps on the unit, but with "only" 1080w of panel, before any loss or derating, I know I won't see that).
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  • tons001
    tons001 Solar Expert Posts: 71 ✭✭
    #2
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    Re: "quick" wiring question...

    A 100amp fuse/breaker is what the SureSine manual recommends between it and the battery. It also calls for a 3 amp fuse on the AC output.

    You might want to get Midnite Big Baby box with some of the din rail breakers for the input and output of the Classic.
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  • zoneblue
    zoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    #3
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    Re: "quick" wiring question...
    tons001 wrote: »
    A 100amp fuse/breaker is what the SureSine manual recommends between it and the battery. It also calls for a 3 amp fuse on the AC output.

    You might want to get Midnite Big Baby box with some of the din rail breakers for the input and output of the Classic.

    Those busman breakers arent nearly as a good as the carling/qbo breakers, and they arent even cheap. Being sealed units theres no where for the arc to go, and being thermal they are slower then magnetic.

    Tons is spot on, get one of the baby box series which have room for 4 13mm wide DIN breakers. 1x13mm for the classic input, another for the classic output, and youll need the remaining double wide spot for the 100A qbo breaker which are 26mm. Perfect. Total cost incl the box under a hundred bucks.

    Be mindful that all breakers go positive/"line" side nearest the battery, regardless of what else might make sense to you. Check out NAWs for all that kit, 5% sale on for the weekend!
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #4
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    Re: "quick" wiring question...

    I ran my Suresines (2 of them) on 60 amp fuses for several years with no problems whatever. Did finally change those fuses for Blue Sea bolted 100 amp fuses thinking it might allow bigger surge before the inverters kicked out, but I have to say, if it did make a difference, I couldn't detect it.
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  • couchsachraga
    couchsachraga Solar Expert Posts: 84 ✭✭
    #5
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    Re: "quick" wiring question...

    Thank you for the quick responses!

    I actually already have the 100 amp fuse for the Suresine - this is putting in a bigger breaker (to go along with the bigger batteries and much bigger panels) for anything coming off the battery.

    I'll look for the baby box - I found the mini, which without fuses was pushing $170.
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  • tons001
    tons001 Solar Expert Posts: 71 ✭✭
    #6
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    Re: "quick" wiring question...
    couchsachraga wrote: »
    Thank you for the quick responses!

    I actually already have the 100 amp fuse for the Suresine - this is putting in a bigger breaker (to go along with the bigger batteries and much bigger panels) for anything coming off the battery.

    I'll look for the baby box - I found the mini, which without fuses was pushing $170.

    $35 here NAWS and the breakers are affordable too. Remember that the breakers are polarity sensitive meaning the (+) needs to go to the battery. I would have screwed that up had BB not brought it to my attention 6 months ago.
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  • mtdoc
    mtdoc Solar Expert Posts: 600 ✭✭
    #7
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    Re: "quick" wiring question...
    tons001 wrote: »
    Remember that the breakers are polarity sensitive meaning the (+) needs to go to the battery. I would have screwed that up had BB
    not brought it to my attention 6 months ago.

    And
    zoneblue wrote: »
    Be mindful that all breakers go positive/"line" side nearest the battery, regardless of what else might make sense to you. Check out NAWs for all that kit, 5% sale on for the weekend!


    It's not quite as simple as "plus side always goes toward battery". It does go to the side with highest potential - so that if placed between PV panel and charge controller (such as in a combiner box), the plus side is the side the PV positive output wire goes in. Confusing, I know..
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #8
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    Re: "quick" wiring question...
    mtdoc wrote: »
    It's not quite as simple as "plus side always goes toward battery". It does go to the side with highest potential - so that if placed between PV panel and charge controller (such as in a combiner box), the plus side is the side the PV positive output wire goes in. Confusing, I know..

    I'm not so sure about that.... To the extent that the breakers in the combiner box are switches (to disconnect individual strings) you are correct.

    However, their more important function is for overcurrent protection. The only way they will trip in this case is if a panel is shorted and the other parallel strings are backfeeding it. In this case the minus side of the breaker goes to the positive side of the string.

    Here is the wiring diagram from my Midnite MNPV3 combiner:
    Attachment not found.
    The plus side of the breaker is connected to the PV positive in this diagram, so Midnite configures their combiner breakers as disconnects.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • couchsachraga
    couchsachraga Solar Expert Posts: 84 ✭✭
    #9
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    Re: "quick" wiring question...

    I do not have a combiner box - there will be only 1 string.
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  • mtdoc
    mtdoc Solar Expert Posts: 600 ✭✭
    #10
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    Re: "quick" wiring question...

    See THIS discussion and explanation by the Midnite guys.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #11
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    Re: "quick" wiring question...

    Just to be clear--"Potential" means Voltage in electronics.

    Here, "Potential" is means which source has the most available current. For example, the battery bank or the PV Array common + bus (which means, I think, I disagree with the instructions that say to put the + towards the panel).

    Newer DC breakers are supposed to not be polarity sensitive--So hopefully that will reduce the confusion/possibility of wiring errors.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • YehoshuaAgapao
    YehoshuaAgapao Solar Expert Posts: 280 ✭✭
    #12
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    Re: "quick" wiring question...
    couchsachraga wrote: »
    Any reason NOT to use one of these?

    http://www.amazon.com/gp/product/B0051P01BW/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=A1UNWS4MSNTF2A

    (Blue Sea 285 series 100 amp DC breaker)

    100 amps is WAY more than my system draws obviously, though I'm not sure exactly what the maximum amps my Midnite Classic 200 will be putting IN to the batteries either (maximum output is 79 amps on the unit, but with "only" 1080w of panel, before any loss or derating, I know I won't see that).


    I see no reason as long as your inverter would not draw more than 80A at max capacity (20% derating for continuous load) and that your battery wiring can handle 100A.
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