Roof mounted DC disconnect tips?

cgeiser
cgeiser Registered Users Posts: 7 ✭
in PV Installers Forum - NEC, Wiring, Installation #1
The inspector is requiring that I put a roof mounted DC disconnect so the fire department can eliminate voltage on the EMT protected DC lines going through the house to the inverter. There is no handy place to mount the disconnect vertically. Does anyone know if it is legal to mount it on its back on a 22degree sloped roof? It would still drain properly and by my figuring would be just as waterproof as when mounted on a wall.

Also, any tips on how to mount it? I obviously don't want to just screw it to the roof with the screws going through a glob of mastic. I was thinking of a rack built on top of three stand-offs. These would be the same kind of standoffs used to mount the solar rails and I would put a small unistrut rack on top of these standoffs in a T shape with the disconnect laying on top of this rack.

If anyone has any tips or even pics of how they solve this problem I would greatly appreciate it.

Thanks,
Che
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Comments

  • solartek
    solartek Solar Expert Posts: 69 ✭✭✭✭
    #2
    Re: Roof mounted DC disconnect tips?

    Che,

    Where are you located? I might try "pointing" out to the inspector sections 690.31(E) and 690.14 of the 2008 NEC which allow you to place the DC disconnect in a more readily accessible location in your situation.

    Scott.
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  • cgeiser
    cgeiser Registered Users Posts: 7 ✭
    #3
    Re: Roof mounted DC disconnect tips?

    Thanks for the advice. I already tried this and spoke withthe fire department. Hey wrote an email stating that they would not require it. The inspector still wants it. I don't want to get involved in the right/wrong aspect of this though, I just need a solution.
    Che
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  • cgeiser
    cgeiser Registered Users Posts: 7 ✭
    #4
    Re: Roof mounted DC disconnect tips?

    Oh, and the job is in the North Bay Area.
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  • stevend
    stevend Solar Expert Posts: 34 ✭
    #5
    Re: Roof mounted DC disconnect tips?

    We put the disconnects in a box, such as these:
    http://www.midnitesolar.com/products.php?menuItem=products&productCat_ID=9&productCatName=PV Combiners
    Just checked their docs and they can be anywhere from vertical to a 3/12 (14 degrees) pitch roof, so your roof is okay (22 degrees is 5/12). Any similar box would do. These ones are held closed with a screw, so that might be a problem for the inspector since firemen might not have a screwdriver handy.

    If you mean North Bay, Ontario, Canada, the Ontario electrical code states that disconnects must be in an easily accessible area, so not a roof. But as you say, you're inspector's insisting on it.
    -Steve
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #6
    Re: Roof mounted DC disconnect tips?

    Maybe the inspector can steer your toward what what he considers "OK", or maybe you might have to go over his head (if this is the last thing you ever need inspected !
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,637 admin
    #7
    Re: Roof mounted DC disconnect tips?

    I think that "North Bay" here is San Francisco, California, North Bay.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • cgeiser
    cgeiser Registered Users Posts: 7 ✭
    #8
    Re: Roof mounted DC disconnect tips?

    Thanks for the suggestions. Steve, something like that is what I plan on using. What I don't have is a great way to mount it. The roof is comp shingle and I need to mount this disconnect on the comp shingle roof somehow.

    The residence is in Marin County, Calif.

    Thanks again,
    Che
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  • stevend
    stevend Solar Expert Posts: 34 ✭
    #9
    Re: Roof mounted DC disconnect tips?
    cgeiser wrote: »
    What I don't have is a great way to mount it. The roof is comp shingle and I need to mount this disconnect on the comp shingle roof somehow.

    What about bolting it to your solar array rails or whatever you have? If you have U shaped rails and they're not long enough, you could always extend them using a splice or something.
    -Steve
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  • cgeiser
    cgeiser Registered Users Posts: 7 ✭
    #10
    Re: Roof mounted DC disconnect tips?

    Bolting to the rails was my first thought. But the rails are not listed for support of anything other than the solar panels and I would likely get called on this.
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  • cgeiser
    cgeiser Registered Users Posts: 7 ✭
    #11
    Re: Roof mounted DC disconnect tips?

    I'm really trying to get this sorted out with a good solution as I believe this is likely to become a more common requirement, at least in the Bay Area.
    Thanks again for the suggestions. Keep 'em coming.
    Che
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #12
    Re: Roof mounted DC disconnect tips?

    you better ask the inspector as to his recommendations on mounting it. it'll make him feel important that you're asking him and seeing as how it would be his recommendation then it won't get turned down on inspection.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,637 admin
    #13
    Re: Roof mounted DC disconnect tips?

    Solar panels usually require a solid surface (non-flexing) mounts so that they don't get torqued/broken.

    If you can mount the power box so that the rails are not twisted (during operation or by environmental sources -- pulling conduit, wind loading, etc.)--He should be OK... Also, the engineer that signed off on the permit may have some information too.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • BillF
    BillF Solar Expert Posts: 48 ✭✭
    #14
    Re: Roof mounted DC disconnect tips?

    I have used a RSTC "SolaDeck" combiner/enclosure box in prior installs that works very well in transitioning USE cable to conduit. It is limited to 4 circuits. It is rugged and looks very good on a roof.
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  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #15
    Re: Roof mounted DC disconnect tips?

    Well, there's always this overkill gizmo:

    http://www.imperial-metals.com/Products/Electraport/brochure-electraport.pdf


    Probably, I'd just go with the tried and true "build a bracket out of slotted angle iron" approach.
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  • System2
    System2 Posts: 6,290 admin
    #16
    Re: Roof mounted DC disconnect tips?

    Hi Che,
    We have the same problem with the inspector and fire department, they don't want to hear about combiner box they want to have a DC disconnect with handler. We install it using an L, unistrat and another piece of unistrat to make a T, i'll try to found a pic to send it to you.
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  • cgeiser
    cgeiser Registered Users Posts: 7 ✭
    #17
    Re: Roof mounted DC disconnect tips?

    Thanks for the tip. I ended up just running conduit on the exterior of the building so no roof mounted disconnect required.
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  • Robin Gudgel
    Robin Gudgel Registered Users, Solar Expert Posts: 58 ✭✭
    #18
    Re: Roof mounted DC disconnect tips?

    I see a lot of discussion about a subject that MidNite has been working on for some time. Inspectors and firefighters are going to love this series of products. Look for them early next year.
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,917 ✭✭✭✭✭✭
    #19
    Re: Roof mounted DC disconnect tips?

    On my wish list is a 600v to 1KV disconnect that is small and less industrial than the common Square D. You know something that would not scare women....
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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