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    techie2u's Avatar
    techie2u Posts: 8, Reputation: 1
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    #1

    Mar 27, 2014, 01:06 PM
    What wire size and type for 250' underground 20 amp circuit
    I live on Lake Lanier in Georgia. I want to run a power with a copper ground wire underground from my house to a floating dock 250' away to supply a 20 amp circuit. What type and size wire do I need to buy?
    donf's Avatar
    donf Posts: 5,679, Reputation: 582
    Printers & Electronics Expert
    		  
    #2

    Mar 27, 2014, 04:14 PM
    Just on the pure math, a 250' run of UF cable will require a size 4 AWG cable.

    However, there is much more needed, not the least of which is weatherproof box, GFCI protection and probably more. I have never dealt with Marina or dockside installations.

    I am sure someone can give a much better answer than I.
    ma0641's Avatar
    ma0641 Posts: 15,675, Reputation: 1012
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    #3

    Mar 27, 2014, 05:11 PM
    My calculator, Southwire, shows a #6 will give you 20 amps with 3.69% voltage drop. You do not want to exceed that drop value. As Don notes, #4 would be optimal but more costly.
    techie2u's Avatar
    techie2u Posts: 8, Reputation: 1
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    #4

    Mar 28, 2014, 11:19 AM
    Quote Originally Posted by donf View Post
    Just on the pure math, a 250' run of UF cable will require a size 4 AWG cable.

    However, there is much more needed, not the least of which is weatherproof box, GFCI protection and probably more. I have never dealt with Marina or dockside installations.

    I am sure someone can give a much better answer than I.
    Thank you very much. As I looked more indepth I found the regulations for a GFI and weatherproof box.

    Thanks again, Techie2u
    techie2u's Avatar
    techie2u Posts: 8, Reputation: 1
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    #5

    Mar 28, 2014, 11:19 AM
    Quote Originally Posted by ma0641 View Post
    My calculator, Southwire, shows a #6 will give you 20 amps with 3.69% voltage drop. You do not want to exceed that drop value. As Don notes, #4 would be optimal but more costly.
    Thank you this was a help.
    Techie2u
    HowHardCanItBe's Avatar
    HowHardCanItBe Posts: 46, Reputation: 2
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    #6

    Mar 28, 2014, 01:10 PM
    Type UF like Don mentioned can be buried directly in dirt; another option would a conduit with individual conductors.

    You might consider using a GFIC breaker to avoid nusiance tripping caused by condensation getting into a GFIC receptacle. They make nice single twist-lock receptacles that form a weather resistant seal.

    I'd also consider running the underground portion to the shoreline, into a weatherproof disconnect switch. Then continue to the dock using either #12 extra-hard usage type SO cord, or liquid-tight flex with indivdual conductors inside. Everything needs to be designed for wet locations.
    techie2u's Avatar
    techie2u Posts: 8, Reputation: 1
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    #7

    Apr 3, 2014, 07:25 AM
    Quote Originally Posted by HowHardCanItBe View Post
    Type UF like Don mentioned can be buried directly in dirt; another option would a conduit with individual conductors.

    You might consider using a GFIC breaker to avoid nusiance tripping caused by condensation getting into a GFIC receptacle. They make nice single twist-lock receptacles that form a weather resistant seal.

    I'd also consider running the underground portion to the shoreline, into a weatherproof disconnect switch. Then continue to the dock using either #12 extra-hard usage type SO cord, or liquid-tight flex with indivdual conductors inside. Everything needs to be designed for wet locations.
    Very good information. I appreciate all the great responses. I think I am ready to proceed with the project. Thank you very much.
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