Using Load center for BOTH 120v and 12v?

santaigosantaigo Registered Users Posts: 22 ✭✭

Here is a SquareD QO 100 amp load center with two hot busses and 6 slots. In a small off grid system, is there any reason why I can't make one bus (top in the photo) 120v and the other bus as breakers form my two PV (195 watts, 12 v, 13 amp each).
Square D help line says that the breakers for this box will handle up to 48 volts DC. In essence, this would be my "fused-combiner" box for the two panels and still have three 15 amp circuits for the cabin, which is plenty.

When I essplained all this to the help guy at Square D he was quiet for some time and finally said "well, I can't recommend you do this, and it won't pass inspection but probably will be fine".

Will this work??:roll:


  • halfcrazyhalfcrazy Solar Expert Posts: 720 ✭✭✭
    Re: Using Load center for BOTH 120v and 12v?

    Will it work?
    Short answer is yes.

    Should you do it?
    Absolutely not. In my opinion there is way to much chance for really bad things to happen here to save 20 bucks or so.
  • VicVic Solar Expert Posts: 3,172 ✭✭✭✭
    Re: Using Load center for BOTH 120v and 12v?

    Half beat me to the punch. If you are CAREFUL, should work. It is NOT code. I would not do it.

    Midnite offers very affordable breakers, and small boxes, like the 'Baby' box and the 'Big Baby' (IIRC), which could perform the indoor combiner box duty. These are sold by the host of this fine site at very reasonable prices.

    The DIN Rail breakers used in these boxes have screw terminals for both the input and output wiring, which I much perfer over the push-on-bus connections in most consumer grade load centers.

    Good Luck, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 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.
  • n3qikn3qik Solar Expert Posts: 741 ✭✭
    Re: Using Load center for BOTH 120v and 12v?

    For $ 18.77 would get a second load center. When, not if, you mix up 12 & 120 source. You are going to do more than $ 20.00 in damaged.

    I am using one as my battery/solar/charger combiner.
  • santaigosantaigo Registered Users Posts: 22 ✭✭
    Re: Using Load center for BOTH 120v and 12v?

    Thanks guys - I kind of assumed this was a bad idea - I'll get another load center to act as my combiner box.
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