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Thread: Boat lifts

  1. #1
    Join Date
    Jul 2015
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    Wilmington, NC USA
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    239

    Boat lifts

    OK, I was in a CE class yesterday and got into a discussion with another contractor about wiring boat lifts. We specifically discussed how the conduit was installed between the inboard pilings and outboard pilings (where the lift motors are installed). With the blessings (actually the idea came from an inspector) of inspectors I have in the past weighted PVC conduit (3/4") by installing them through the holes in building bricks and wire tying them so they didn't slide around too much, one every 4'-5'. Strapped the conduits at low tide water line and the rest of the conduit below the low water level was unsupported. Passed inspection.

    This guy really gets into his work (I was quite impressed). He puts on scuba gear, goes down to the bottom and digs a 4"-6" trench and installs the conduit, he also straps the conduit to the piling below the low water level.

    I'm throwing this on the forum just for conversation and comments. I commend this gentleman for his dedication to a quality installation, but ..... do you think he's taking it a bit too far? Do you think the conduit weighting is wrong (even though it passes inspection)?

  2. #2
    Join Date
    May 2005
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    Tacoma, WA
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    How many boat lift motors are there? Is there one on each corner? How far is it from the dock?

  3. #3
    Join Date
    Jul 2006
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    2,351
    Could be he just likes diving; I've know people that will take almost any excuse to get in the water.

  4. #4
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    Jul 2015
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    Wilmington, NC USA
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    It would look something like this, 2 motors, one side up against the dock, the other side 10-12' or so.



    '

  5. #5
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    Jan 2016
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    Jax, Fl
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    Quote Originally Posted by oldsparky52 View Post
    It would look something like this, 2 motors, one side up against the dock, the other side 10-12' or so.



    '
    I don't think a 4-6" trench under water is gonna last with tides and prop from the boat washing sand. If it's weighted it should stay in place. That's how we do it and never had an issue. Just strap conduit at low tide.

  6. #6
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    Jul 2015
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    Quote Originally Posted by 1haz View Post
    I don't think a 4-6" trench under water is gonna last with tides and prop from the boat washing sand. If it's weighted it should stay in place. That's how we do it and never had an issue. Just strap conduit at low tide.
    I think the trench will last because the sand tends to accumulate, but if they (boat owner) "blew out" the slip, then you are spot on. Bottom line for me is my way passes inspection, I've not heard about problems, and I don't need to go swimming, lol.

  7. #7
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    Jun 2003
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    Hawthorne, New York NEC: 2014
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    What's the cover required by the NEC for underwater sch 40 PVC conduit?

    -Hal

  8. #8
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    Jul 2015
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    Quote Originally Posted by hbiss View Post
    What's the cover required by the NEC for underwater sch 40 PVC conduit?

    -Hal
    Funny, I asked the guy what he used for determining the correct burial depth.

  9. #9
    Join Date
    May 2005
    Location
    Tacoma, WA
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    Quote Originally Posted by 1haz View Post
    I don't think a 4-6" trench under water is gonna last with tides and prop from the boat washing sand. If it's weighted it should stay in place. That's how we do it and never had an issue. Just strap conduit at low tide.
    I would simply lay Type G or G-GC cable on the bottom of the sea or lake bed, assuming that the water level never gets to the point where it is exposed or could be subject to physical damage. I'd put it in a PVC conduit sleeve as it comes up on the side of the piling.

    We use Type G and G-GC cable for marina work all the time, and it is used in mines, it's VERY durable stuff. It's flexible too, which is important in a marine environment.

  10. #10
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    Quote Originally Posted by buzzbar View Post
    I would simply lay Type G or G-GC cable on the bottom of the sea or lake bed, assuming that the water level never gets to the point where it is exposed or could be subject to physical damage. I'd put it in a PVC conduit sleeve as it comes up on the side of the piling.

    We use Type G and G-GC cable for marina work all the time, and it is used in mines, it's VERY durable stuff. It's flexible too, which is important in a marine environment.

    Kind of a pricey way to wire that since G and G-GC don't come smaller than #8 and you can get by with (5) #14's to the motor instead of #8's.

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