Question about Midnite circuit breaker ratings

Plowman
Plowman Solar Expert Posts: 203 ✭✭✭✭✭
in Solar Beginners Corner #1
I just received four Midnite Solar 12 amp circuit breakers from NAWS. I plan on using these in a combiner box for four Dmsolar 158W panels wired in parallel. Panels have an Imp of 8.47 amps, max rated series current is 15 amps.

These 12 amp breakers say the "trip amps" is 15.6. Why the difference? I've always assumed a 12 amp breaker would trip at 12 amps, but I was apparently wrong in that assumption.

Either way it works for my application, just curious.
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  • zoneblue
    zoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    #2
    Re: Question about Midnite circuit breaker ratings

    The CBi breakers are full load rated. That means that they can carry their rated load indefinately without get hot, exploding... or tripping. Download the manual for those and you can see the trip curves. You want the QY curves.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


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  • CDN_VT
    CDN_VT Solar Expert Posts: 492 ✭✭✭
    #3
    Re: Question about Midnite circuit breaker ratings

    And for installation , of these , I take a wire / cable of strands , arrange them flat and hit them so the round is gone & they become slightly rectangular or have a flatter side.
    Then RIGHT after they get crimped into the breaker. They have poor screw crimping without I found out . Use to Square / stab , breakers , crimping force much greater .

    VT
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #4
    Re: Question about Midnite circuit breaker ratings

    VT,

    Personally, I have had NO problems, whatsoever with the MN CBI DC DIN-Rail breakers (MNEPVs).

    I have had issues with the CBI AC breakers, and would - personally - avoid using them if possible.

    YMMV, FWIW, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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  • Plowman
    Plowman Solar Expert Posts: 203 ✭✭✭✭✭
    #5
    Re: Question about Midnite circuit breaker ratings
    zoneblue wrote: »
    The CBi breakers are full load rated. That means that they can carry their rated load indefinately without get hot, exploding... or tripping. Download the manual for those and you can see the trip curves. You want the QY curves.
    OK, that makes sense, thanks.
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  • CDN_VT
    CDN_VT Solar Expert Posts: 492 ✭✭✭
    #6
    Re: Question about Midnite circuit breaker ratings

    Vic , Is just I have had saddle style type not squeeze tight enough , so on installation I found some of the round strands came loose .after a flattening, NOT crushing them to have a weak (high Resistance spot) I found that after a few workings of the wires in the boxes less needed another tightening crimp of the set screw.

    Just some things I've run into on the MN DC Breakers ..

    VT
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