DC Circuit Breakers Recommendation?

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ki7fx
ki7fx Registered Users Posts: 10 ✭
in Solar Beginners Corner #1
I am using a DIN Rail dc circuit breaker and Midnite "baby box" from NAWS for DC protection on one circuit of my solar system.

However, I really don't like this setup as my 6g cable seems to over-power the small DIN rail setup (the breaker flops around too much inside the box unless the cover/faceplate holds it in place). In one case, the breaker came off the rail in the combiner box and hit the box frame. I was glad to see it worked as advertised :-)

I have seen some nice single and double pole DC breakers from Blue Sea, but can't seem to locate a suitable box to hold them & this is one area that I don't want to mess with "homemade" stuff, ya know?

What are you guys using for your DC breaker needs???
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  • boB
    boB Solar Expert Posts: 1,030 ✭✭✭✭
    #2
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    Re: DC Circuit Breakers Recommendation?

    You will need to use a strain relief on 6 gauge wire and also route and bend the wire to reduce stress on the breaker.

    There should be no strain on the breaker prior to tightening the strain relief.

    Did you push in the little yellow lock peace on that DIN rail breaker? If pressed in and locked it should keep it from flopping around hardly at all even without the Dead front on there.

    boB
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  • ki7fx
    ki7fx Registered Users Posts: 10 ✭
    #3
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    Re: DC Circuit Breakers Recommendation?

    Yes, the yellow lock/tab is pushed in and locked but it still seems too loose to be safe. I have routed and twisted the cable as best I can.
    Would you mind explaining the strain relief for this config?

    thanks,
    Mike
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #4
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    Re: DC Circuit Breakers Recommendation?

    Probably along the lines that the cable should be "pre-bent" to enter the breaker and not leave a bunch "torque" on the breaker assembly itself.

    Also, if the wire leaves the box, make sure that the wire is tied down, anchored/etc. so that if somebody starts moving the cable around (to battery bank, to solar array, etc.), it does not lever back into the box and strain the breakers.

    Sometimes the strain relief clamps that go into the holes of the boxes are not enough--You need at least two points (wire clamp to wall a few inches away from box/strain relief).

    Heavy gauge/solid cables can put a fair amount of pressure on their connection points if moved around.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • boB
    boB Solar Expert Posts: 1,030 ✭✭✭✭
    #5
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    Re: DC Circuit Breakers Recommendation?

    6 gauge wire is stiff.

    What you will probably have to do is to get a Romex wire type strain relief from the hardware store, drill a hole in the box and run the wire
    through that strain relief. Those SRs are the ones with 2 screws on either side that pinch the wire to keep it in place.

    Using THHN wire though, it may have a tendency to cut into the insulation so you may want to pad it with something to help
    keep it from doing that.

    Something like this...


    http://solarelectricdistributor.com/shoppingcart/product_images/q/860/05110B__49381_zoom.JPG


    boB
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  • oil pan 4
    oil pan 4 Solar Expert Posts: 767 ✭✭✭✭
    #6
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    Re: DC Circuit Breakers Recommendation?

    I usually use Eaton breakers any time I put a breaker instead of a fuse on circuit.
    If I have a need to hold a heavy stiff wire inside an enclosure I use ALDL clamps when zip ties wont do the job.
    Use the romex style wire holders like boB said when going into a box.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

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  • rgk1
    rgk1 Solar Expert Posts: 134 ✭✭✭
    #7
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    Re: DC Circuit Breakers Recommendation?

    I would double check that the yellow lock tab to make sure its in the locked position and locked to the back side of the DIN rail. Not accidentally locked on the front side leaving the bottom loose. I have 4 gauge on some of mine and dont have a problem. As recommended, bend the wire to a position that will keep the strain off the breaker.
    4-Risen 320 watt in series/parallel, 8-215ah 6 volt GC2 batteries in series, Exeltech 1100 watt/48 volt inverter, Tristar 45 MPPT controller.
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  • raydias
    raydias Solar Expert Posts: 68 ✭✭✭✭
    #8
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    Re: DC Circuit Breakers Recommendation?

    Also ensure the + bus bar at the top is tightened down with the top screw of the breaker.
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