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Thread: Power line going to workshop is too low?

  1. #31
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    Quote Originally Posted by John K Jordan View Post
    Electricians have mentioned every underground conduit somehow gets full of water, no matter how well the conduit joints are sealed. Apparently water hurts nothing. The conduit is for protecting the insulation from physical damage.
    Any underground is a wet location. The water does not come from the soil or joints, but from the air.
    The temp, 18”, 24” whatever below grade is different than above ground. Unless the conduit and the termination points of the conduit are exactly the same temperature, you have a convection current. May not be strong, but it is constant. The air is always changing.
    Anytime that subterranean conduit temp is lower than the dew point of the above ground air, the water vapor condenses.

    A hot humid day, you get a few drops of condensation. A few here, a couple there... after a few weeks, you have a wet location.
    Last edited by Charlie Velasquez; 10-29-2020 at 9:17 AM. Reason: clarity
    Comments made here are my own and, according to my children, do not reflect the opinions of any other person... anywhere, anytime.

  2. #32
    Travis that's correct the enclosures are not waterproof the wire is. So it's likely that the water is connecting terminations that should not be connected.

    Quote Originally Posted by Travis Conner View Post
    I live by the water now Jim and everytime we have a hurricane and the water comes up 4ft or so I can guarantee the power will go out. I'm not sure if the transformer (green boxes) are going under water or what, but they usually have it back on in 2 or 3 hours. I do believe their is a 240/120 transformer box right next to the bulkhead in my neighborhood so that means it's about 4ft above the canal. lol

  3. #33
    Frank,
    We have had those too. We avoid pulling wire, if possible, in late winter when the pipes are likely to have significant ice in them. Gotta call the locates glad nobody got hurt. We require open trench near primaries but that only helps when they call the locates in or ask about a utility atlas for their dig location.
    Daniel

  4. #34
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    There's no sunlight underground to dry things out underground. I guess if you only have a short run where you can run it without having a connection underground then it would stay dry, but my guess is they bend the pipe then install a straight pipe after that, so there goes your seemless connection.

  5. #35
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    Quote Originally Posted by Travis Conner View Post
    There's no sunlight underground to dry things out underground. I guess if you only have a short run where you can run it without having a connection underground then it would stay dry, but my guess is they bend the pipe then install a straight pipe after that, so there goes your seemless connection.
    Even if you had perfectly water tight joints in the pipe, it would still get wet from condensation in the pipe from warm, humid topside air migrating into the conduit.

  6. #36
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    Quote Originally Posted by Frank Pratt View Post
    .... 4 conductors of 750 MCM RW90 aluminum in concrete encased 4" PVC conduit. ...
    I've given up on aluminum wire. I had a 4-conducctor direct burial aluminum feed fail after a number of years - no digging or external disruption of the insulation. One conductor went first, the others followed over a few weeks. Best we could figure was a rock or two worked into the insulation over the years or the insulation came damaged or was nicked during installation. Aluminum corrodes to powder. I didn't bother to dig it up but dug another parallel trench. I don't care if aluminum is way cheaper, for me it's copper in conduit from now on. I even run direct burial copper cable in conduit to help protect it from wayward shovels and such.

    JKJ

  7. #37
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    Quote Originally Posted by John K Jordan View Post
    I've given up on aluminum wire. I had a 4-conducctor direct burial aluminum feed fail after a number of years - no digging or external disruption of the insulation. One conductor went first, the others followed over a few weeks. Best we could figure was a rock or two worked into the insulation over the years or the insulation came damaged or was nicked during installation. Aluminum corrodes to powder. I didn't bother to dig it up but dug another parallel trench. I don't care if aluminum is way cheaper, for me it's copper in conduit from now on. I even run direct burial copper cable in conduit to help protect it from wayward shovels and such.

    JKJ
    The cost difference is just to great to write off aluminum, especially with larger feeders. Aluminum simply will not fail if installed correctly. Direct bury cable needs to be properly bedded if not in conduit. If you do get a fail in direct buried cable, it's not a huge deal to splice it in situ. A locator can pinpoint the location very closely. Hand dig it up, or hydro-vac it to expose the cable.

    I've done several dozen underground splices back in the day when they'd just let you throw it in the ground & back fill it. Now code requires the conduit or sand bedding. Personally, I always go for the conduit and bedding as well if it's at all rocky.

  8. #38
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    Quote Originally Posted by Frank Pratt View Post
    The cost difference is just to great to write off aluminum, especially with larger feeders. Aluminum simply will not fail if installed correctly. Direct bury cable needs to be properly bedded if not in conduit. If you do get a fail in direct buried cable, it's not a huge deal to splice it in situ. A locator can pinpoint the location very closely. Hand dig it up, or hydro-vac it to expose the cable.

    I've done several dozen underground splices back in the day when they'd just let you throw it in the ground & back fill it. Now code requires the conduit or sand bedding. Personally, I always go for the conduit and bedding as well if it's at all rocky.
    My ground was topsoil and red clay, very few rocks. I bedded the cable in sand. A locator showed the first conductor failed first in one place then a few days later in a second and possibly a third place. Very odd. (I could watch the voltage decrease by the hour.) A few days later the second conductor failed. For a while I ran power on the smaller common and ground to the panel, enough to keep the electric gate powered (The gate was another 450' underground, copper in conduit already). Then the third conductor failed. That multiple conductors failed confused all the experts I consulted. The best guess was I was sold some bad cable.

    I gave up and dug a new trench and laid copper in conduit, over sized for 80+ amps, far more power than I needed. I didn't care what it cost - I just didn't want it to fail again. The remote panel is at the site of a future equipment building.

    Since I had the equipment and the time the only cost was the wire, conduit, and the diesel fuel.

    trackhoe_trench2.jpg trackhoe_trench_long.jpg trackhoe_conduit.jpg

    The run to the first panel box was almost 700'. For temporarily power while laying the new line I ran 100's of feet of extension cord to keep the security gate batteries charged. The aluminum is still in the ground if anyone wants to pull it up. Probably worth something for scrap.

    JKJ
    Last edited by John K Jordan; 10-29-2020 at 9:56 PM.

  9. #39
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    I can understand why you just replaced the whole run. When you have that many points of failure happen like that, it's best to just cut your losses.

  10. #40
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    All they need to do is tighten the cable and it can be raised up another 2ft or so.

  11. #41
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    Quote Originally Posted by Travis Conner View Post
    All they need to do is tighten the cable and it can be raised up another 2ft or so.
    I had that issue awhile ago here for our home...it took me nearly two years to be able to get the power company to tighten up the cable and the final straw was a tree limb falling and ripping it loose, all this despite the fact that the cable actually crossed the busy state road to get to the pole and that the length of the line is long enough that I could nearly touch it at the halfway point. Be persistent....
    --

    The most expensive tool is the one you buy "cheaply" and often...

  12. #42
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    I wonder how often the wire gets damaged from being run through the conduit. Like if you don't have a helper to feed it through while you pull. I pulled out some thhn wire that had the outer plastic jacket torn one time. Nothing wrong with it, but still.

  13. #43
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    Quote Originally Posted by Travis Conner View Post
    I wonder how often the wire gets damaged from being run through the conduit. Like if you don't have a helper to feed it through while you pull. I pulled out some thhn wire that had the outer plastic jacket torn one time. Nothing wrong with it, but still.
    I put heavy wire through conduit a different way. I lay the wire bundle in or beside the trench then feed the conduit one length at a time down the wire and glue it to the last one. Then I fill in the trench. This requires a lot of walking for a long run but I think it is a lot simpler than pulling large conductors. Can't damages insulation. So far I've installed about 1500' in three runs this way here at the farm.

  14. #44
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    Quote Originally Posted by John K Jordan View Post
    I put heavy wire through conduit a different way. I lay the wire bundle in or beside the trench then feed the conduit one length at a time down the wire and glue it to the last one. Then I fill in the trench. This requires a lot of walking for a long run but I think it is a lot simpler than pulling large conductors. Can't damages insulation. So far I've installed about 1500' in three runs this way here at the farm.
    NEC frowns on this.
    The pvc conduit and the polyvinyl insulation are close enough that the cement can compromise the insulation. Even fumes, according to people on the Mike Holt forum.

    The interior of the bells are beveled, any cuts should be field beveled. Bells should go in the direction of the pull. The head of the pull should be tapered and taped, starting from the conductors and taped toward the head, or use a pulling sock. Offset the conductors, and on 6awg and smaller consider offsetting, stripping some insulation, and bending back before taping to the body of the conductors making a rounded head on each conductor. Keep the conductors kink-free. Keep dirt out of the conduit, add pulling conduit bodies on long runs... and lube... lots and lots of lube.
    Comments made here are my own and, according to my children, do not reflect the opinions of any other person... anywhere, anytime.

  15. #45
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    Quote Originally Posted by Charlie Velasquez View Post
    NEC frowns on this.
    The pvc conduit and the polyvinyl insulation are close enough that the cement can compromise the insulation. Even fumes, according to people on the Mike Holt forum.

    The interior of the bells are beveled, any cuts should be field beveled. Bells should go in the direction of the pull. The head of the pull should be tapered and taped, starting from the conductors and taped toward the head, or use a pulling sock. Offset the conductors, and on 6awg and smaller consider offsetting, stripping some insulation, and bending back before taping to the body of the conductors making a rounded head on each conductor. Keep the conductors kink-free. Keep dirt out of the conduit, add pulling conduit bodies on long runs... and lube... lots and lots of lube.
    Thanks. I wondered if the glue would soften the insulation so I globbed some on as a test. I couldn't detect any affect. Maybe it depends on the cable, maker, different formulations of insulation, the temperature, the phase of the moon, who knows. I just tried it on the power conductors, not the green insulation on the ground wire.

    JKJ

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