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junction between PV cables and THWN in conduit

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  • bob-n
    replied
    Yes, I learned that lesson the hard way, too. Undried silicone is a yucky mess.

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  • RShackleford
    replied
    Originally posted by bob-n View Post
    You're right. GE Silicone II appears to be neutral cure. They refer to it as GE Silicone 2+ below, but I think that's the same thing. Great to know. Thank you.
    https://www.gesealants.com/Frequentl...questions.aspx
    I didn't try to use the Silicon2 on wirenuts, rest assured.

    However, I did try to use an old tube of it for something else, and it was a rude shock. It never cured, and just turned into this nasty black grease. I complained to GE and they basically said "tough titty, it's only guaranteed for 3 years". Evidently the catalyst that causes curing wears out.

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  • bob-n
    replied
    You're right. GE Silicone II appears to be neutral cure. They refer to it as GE Silicone 2+ below, but I think that's the same thing. Great to know. Thank you.
    https://www.gesealants.com/Frequentl...questions.aspx

    Leave a comment:


  • RShackleford
    replied
    Originally posted by bob-n View Post
    Glad it worked out. I think old PVC is more brittle than new stuff. That makes me wonder about installing something with a 25 year rated life and using plastic accessories.
    Perhaps it's sunlight (UV) that makes it become brittle, and since it's shaded under the panels it'll be ok ? Hopefully ...


    Regarding your question about newer silicone not being corrosive, it's not a new/old thing. There are different formulations for different purposes.
    I didn't necessarily mean new/old. I actually meant the GE Silicone II product (which I assumed, perhaps erroneously, was newer that the original silicon caulks). Can't find too much real data on it, except that it's "low odor" which I can confirm it doesn't have that typical vinegar odor.

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  • bob-n
    replied
    Glad it worked out. I think old PVC is more brittle than new stuff. That makes me wonder about installing something with a 25 year rated life and using plastic accessories. Time will tell.

    Regarding your question about newer silicone not being corrosive, it's not a new/old thing. There are different formulations for different purposes. Hardware-store silicone caulk and sealant is corrosive (acetic acid curing aka acetoxy). There are more expensive silicone sealants made for electronic and other sensitive applications that are neutral cure (alcohol curing aka oxime), but these are normally only sold through industrial and electronic distributors.

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  • RShackleford
    replied
    Originally posted by RShackleford View Post
    Hate to mess up the box, $40 or so, and mail order. Rather skip the sealing washer and RTV it.
    Had the proper size forstner bit lying around and it did the countersink like a charm. The Cantex PVC box I used did not seem brittle at all, so no worry there. Just have to be careful with the countersink depth. Dunno why the glands had to make the threads so short though.

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  • RShackleford
    replied
    Originally posted by Ampster View Post
    In one of those big boxes with thicker walls I actually had to counter sink around the hole
    Hate to mess up the box, $40 or so, and mail order. Rather skip the sealing washer and RTV it.


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  • Ampster
    replied
    Originally posted by RShackleford View Post
    Wondering if these will work with the Cantex 8x8x4" box that I bought, with its 3/16" wall thickness - so that there's room for the nut and sealing washing to fit onto the threaded part.
    In one of those big boxes with thicker walls I actually had to counter sink around the hole to make the wall less than 1/8". I forgot which tool I used but I think it was one of my spade bits that had a flat profile and I did it first so I would have a pilot hole for the bigger bit. Then I drilled out for the gland nut thread size.

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  • RShackleford
    replied
    Originally posted by RShackleford View Post
    BTW, where does one find these "glands" ? Can't find anything like 'em at bigbox websites.

    Oh, looks like Amazon has 'em; this looks like a nice assortment: https://www.amazon.com/dp/B01MDTUIIA...2s9dHJ1ZQ&th=1
    Wondering if these will work with the Cantex 8x8x4" box that I bought, with its 3/16" wall thickness - so that there's room for the nut and sealing washing to fit onto the threaded part.

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  • RShackleford
    replied
    Originally posted by RShackleford View Post
    I might run Romex, because the inverter is probably gonna be on the outside wall of the house, and the wires come out the bottom of the inverter, so it may easiest to go down into the crawlspace (using conduit) through the band joist, and then over and up into the load center - so pulling Romex through conduit that short distance may be easier than adding a box inside the band joist to transition from THWN to Romex (or running conduit all the way to the load center.
    Actually AHJ is not ok with this (glad I asked). Only 5ft of "power source conductor" allowed to be on the interior, plus it's required to be in metal conduit.


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  • RShackleford
    replied
    There are 22 degree elbows.
    But I'd probably just bend the end of a full section.
    Indeed, Cantex (and probably others) list a 22-degree elbow. However, it's impossible actually find, around here at least.

    Instead, what I did was to cut off a 45-degree elbow at a spot where there would be the proper bend.


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  • RShackleford
    replied
    Originally posted by Mike90250 View Post
    > Almost seems like you could just use a regular wirenut and squirt some silicon caulk in there.

    NOOOO !!!! Silicone caulk is corrosive to copper, it has a vinegar component to the cure cycle (smell it sometime) The expensive electrical cable rated caulk uses a neutral cure.

    The weatherproof wire nuts use silicone GREASE in them.
    I absolutely accept your answer and will not do this. However, is it not true that some of the newer-type silicon caulks do not use an acetic acid (vinegar smell) cure ?


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  • foo1bar
    replied
    Originally posted by RShackleford View Post
    BTW, where does one find these "glands" ? Can't find anything like 'em at bigbox websites.
    They're a specialty item.

    I used Heyco glands (M3234GBR-SM )

    One of them I even got as a sample.

    Try to make sure you are getting the right size for your cables and your knockouts before you order. (if you're drilling the holes in plastic jbox then you dont' have to worry as much about the knockout size)

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  • SunEagle
    replied
    Originally posted by RShackleford View Post
    BTW, where does one find these "glands" ? Can't find anything like 'em at bigbox websites.

    Oh, looks like Amazon has 'em; this looks like a nice assortment: https://www.amazon.com/dp/B01MDTUIIA...2s9dHJ1ZQ&th=1
    Those glands are what i have used with success.

    Leave a comment:


  • RShackleford
    replied
    BTW, where does one find these "glands" ? Can't find anything like 'em at bigbox websites.

    Oh, looks like Amazon has 'em; this looks like a nice assortment: https://www.amazon.com/dp/B01MDTUIIA...2s9dHJ1ZQ&th=1
    Last edited by RShackleford; 05-14-2020, 07:19 PM.

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