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Almot's avatar
Almot
Explorer III
Aug 16, 2013

Roof J-box for solar - what splicer?

Need some education. Getting all the pieces. Have a 4*2" waterproof PVC combiner box, will run AWG 12 from panels in box, and AWG 8 out to controller. Will use mechanical splicers, for lack of experience.

I can use either these Ground bus bar - it can be screwed to the bottom so the screw will puncture another hole in the roof, don't need more holes.

Or these Splicer-reducer - can't be screwed to bottom.

Q1: which terminal is better? Splicer is - I think - 1.25" long (Home Depot specs are meaningless), so the wire has 1" length inside - good. The box is mere 3.75"x3.75" inside, inserting the wires in the ends will be a tight spot. Bus bar is easier to access, but the wire has mere 0.5" (?) length inside, less contact.

Q2: What if I glue the splicer or bus bar to the bottom? And wedge a wood block between them, to prevent accidental short? Somebody did exactly this, I can't remember who. Initial plan was to wrap the terminal in rubber tape and let it hang in the air, then it would be easier to bend/insert the wire in the ends in case of a splicer.

25 Replies

  • I used the HD ground bus bars cut to length attached to the bottom of the box with flush head nylon screws, nuts and washers. No extra holes in the roof and no leaks since the box is sealed down.
  • If you don't wanna buy THIS, u can enlarge the pic and see how its built.

    Just looked at all your pieces again.
    I would simply drill a hole on the bottom of the J Box and bevel in a flat head screw so its flush, and maybe some JB Weld in the box to hold the buss bar. Since it goes on the roof, simply set the box in a pool of Dicor. It's not going anywhere.
  • Almot's avatar
    Almot
    Explorer III
    How good is thermal durability of JB-weld? There won't be much driving around, but after 100F in the closed box for half a year, will it still hold next year?

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