Junction box on top or bottom?

Plowman
Plowman Solar Expert Posts: 203 ✭✭✭✭✭
in Solar Beginners Corner #1
I'm expanding my little off-grid system and was wondering if it's acceptable to mount a panel in portrait orientation with the junction box at the bottom.

It'd obviously be more resistant to water intrusion if the junction box was at the top, but I'd be saving a fair bit of wire (thus reducing voltage drop) if it was at the bottom. I googled but only found one thread on another board, which had mixed opinions.

What's the answer to this cost-benefit question? Anyone had a problem with water in their junction box? I live in rainy Oregon, so it seems like it might be an issue.
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  • SkiDoo55
    SkiDoo55 Solar Expert Posts: 414 ✭✭✭
    #2
    Re: Junction box on top or bottom?

    Being born and raised in Portland I would follow the panel manufactures guide lines which probably with the junction box at the top. Water will after time wick in thru the cover gasket and wire seals. The extra couple of feet of wire appropriately sized for current and voltage drop.
    GT3.8 w/4600W Trina 230W, TX5000 w/5000W ET-250W, XW4024 w/1500W ET-250W, 4 L16, 5500W Gen. (never had to use) Yet!!
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  • Plowman
    Plowman Solar Expert Posts: 203 ✭✭✭✭✭
    #3
    Re: Junction box on top or bottom?
    SkiDoo55 wrote: »
    Being born and raised in Portland I would follow the panel manufactures guide lines which probably with the junction box at the top. Water will after time wick in thru the cover gasket and wire seals. The extra couple of feet of wire appropriately sized for current and voltage drop.
    My panels are Dmsolar, the manufacturer doesn't say anything about mounting them. Very little documentation in general. In their spec sheet they show a diagram of the panel with the junction box at the top, but there are drain holes on both the top and bottom of the frame.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #4
    Re: Junction box on top or bottom?

    i would agree to put it at the top as moisture will travel the wires to the junction box unless you were to put drip loops on the wires, but if you do that you might as well just put it at the top as the extra wire would've allowed anyway.
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  • Plowman
    Plowman Solar Expert Posts: 203 ✭✭✭✭✭
    #5
    Re: Junction box on top or bottom?

    I just took another look at the cargo trailer on which I'll be mounting my panels (I have one on there now but it's in landscape orientation) and it looks like there'd be no advantage to mounting the junction box on the bottom since I'd have to run the wires to the other side of the trailer where my charge controller and other components are installed. With the junction box on top I'd just run the wires straight down. Total wire run would be roughly the same however I mount the panels, so junction box on top it'll be.

    I did find this little tidbit for others who might have this question:
    Installation with a junction box at the bottom is permitted for modules with junction boxes classified as IP65 or IP68.

    http://www.q-cells.com/uploads/tx_abdownloads/files/Hanwha_QCELLS_Installation_manual_QPRO-G2_QPEAK_series_2013-02_Rev04_AU_02.pdf

    My Dmsolar panels have an IP65 junction box, so looks like they'd be OK to mount at the bottom. Here's a pic of an installation that has them at the top and bottom:

    solar-tracker-system.gif
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
    Re: Junction box on top or bottom?

    in most cases i think you'll be fine with the wires, but there's always that rare instance you'll have to watch for.

    i have not read all posts by you and i probably wouldn't have remembered anyway, but are those mounts tracking or not? pretty fancy.
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  • Plowman
    Plowman Solar Expert Posts: 203 ✭✭✭✭✭
    #7
    Re: Junction box on top or bottom?

    That isn't my system Niel. I wish. Just a pic I got off the interwebs, I believe it's in China.
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