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  • Roof Jbox install ideas?

    Elevated? Flush? How to support?

    I have a 6x6x6 PVC Jbox that I am using to splice Enphase wiring to the 10AWG EMT run to the combiner. I feel that this box is too bulky to be attached to the racking, plus it will make things a little tricky due to the roof sloping. Im still keeping it as a plan B though.

    What are your guys' opinion on mounting flush to the roof, vs elevating it on a conduit support etc? I need ideas for attaching it to the roof. Pictures of your setup would be greatly appreciated.

    This is the jbox in question:

    kraloy.jpg

  • #2
    In general, it's bad practice to put anything on the roof surface other than approved mounts.

    I faced the same problem. Here's how I solved it.

    My array uses Ironridge XR-100 rails and Flashfoot-2 feet. The rails have a smaller T-slot on top to attach to panels and a stronger T-slot on the side to attach to the feet.

    I made a support from 6" x 10" x 3/16" aluminum bent into an L shape. The J-Box bolted down onto the flat portion of the aluminum and the vertical portion of the aluminum bolted to the strong T-slot on the side of one rail with two hardware-store SS bolts. Fortunately, the XR-100 tee-slots are correctly sized for standard size bolt heads.

    The whole assembly - aluminum and J-Box, sits under a panel on the side of the array nearest the disconnect switch, but not so low that it touches the roof.
    JBoxMounting.jpg
    Attached Files
    7kW Roof PV, APsystems QS1 micros, Nissan Leaf EV

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    • #3
      Several companies also make combination junction boxes with flashings that eliminate the need for a separate conduit flashing through the roof. Location may be an issue.
      9 kW solar. Driving EVs since 2012

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      • #4
        Originally posted by Ampster View Post
        Several companies also make combination junction boxes with flashings that eliminate the need for a separate conduit flashing through the roof. Location may be an issue.
        Soladeck is one that comes to mind. One nice thing is you have the option to run the conduit in the attic if wanted with a Soladeck junction/combiner/pass thru box. Wanted to add a link but all links I found are from retailers, not the mfg. website.
        2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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        • #5
          Originally posted by littleharbor View Post
          Wanted to add a link but all links I found are from retailers, not the mfg. website.
          https://rstcenterprises.com/soladeck/

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          • #6
            We have settled on just using the Bell metal "waterproof" j-boxes - usually 2-gang. Plastic just doesn't last the many years your array needs to. These Bell boxes are compact enough to fit under the array. Not enough space for fancy terminal connections so just use Polaris type butt splices (monkey butt connectors) or simple wire nuts (we've never had a problem doing this). By all means, I.D. the wires with appropriate labels so that the next guy can figure out your wiring. We have a rule about not having duplicate wire colors coming down off the array. THHN wire is readily available in six different colors (not including white and gray which are reserved for grounded conductors). We use Red/Blk, Org/Brn, and Yel/Blu typically. Violet/Dk Blu are not so available, but needed occasionally when wiring 4 strings. It is invaluable to have no confusion when hooking up your wiring.
            Also, Drill a weep hole in the lowest part of your j-box - the is no such thing as a waterproof box as condensation will produce amazing amounts of water.
            BSEE, R11, NABCEP, Chevy BoltEV, >2500kW installed

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            • #7
              I ended up returning that PVC Jbox and getting a Soladeck instead.

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