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I have a boathouse on the puget sound in WA. Medium bluff, then house below that on concrete piers. Half the time, it's above a pebbly beach. The other half, it has several feet of saltwater under it. In fact, last winter, between a king tide and storm surge, there was water over the floor/deck. I wasn't there, but a week later, I saw that things had moved around and one paddleboard was gone. Currently, there is a 20A wire from a GFCI breaker at the main panel, 100' to the boathouse. The wire is direct buried (expect where it is exposed!). I'm not even sure it's UF - it may be 12/2 NM. And the path from the main house to the boathouse is down a number (3?) of terraces, so replacing with conduit will mean a number of angles. The GFCI trips pretty much as soon as I turn on the lights. It feeds a number of flood lights inside or outside the boathouse and a number of outlets. The wire is mostly stapled to ceiling joists (with NM staples that are now rusting). But some runs horizontally along walls, and then serves as a "holder" for things stored behind it (!!!). The outlets are normal 15A outlets inside plastic boxes (again, with rust apparent).

I'd like to redo this whole mess to something more safe and code compliant. I'd like to have at least 50A at a subpanel at the boathouse, feeding lights and outlets and possibly a boat lift.

Any feedback on best practices for doing all this in a manner that is more safe, code compliant, and which will live longer in this salty mist filled environment? I know this likely covers a lot of different issues. If I should separate this into separate issues (wire to the boathouse, panel in the boathouse, wiring in the boathouse, outlets in the boathouse), let me know. I just was hoping to avoid replicating the description of the currrent state of affairs.

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  • This would be great place for someone to write up a canonical answer about different building subpanels covering all the extras not in a same building subpanel such as ground rods, conduit + wires vs. direct burial cable, disconnect requirement, etc. and the all-important GFCI question. Sep 8, 2023 at 20:17
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    There's already this saltwater dock question with a lot of info, if some different specifics such as a much longer run. diy.stackexchange.com/q/272841/18078
    – Ecnerwal
    Sep 8, 2023 at 20:40
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    You can avoid describing the problem multiple times by either copying and pasting that section, or by linking additional questions here for detailed background. And they probably should be different questions. Sounds like the existing install is badly done, though you may want to confirm that it's NM running underground (ugh.) Salt water and electricity is hard...
    – Ecnerwal
    Sep 8, 2023 at 21:22
  • @Ecnerwal that one is a voltage drop need transformer situation which is different Sep 8, 2023 at 22:12
  • Okay, so let's start this as a partial answer to the above. What's the best practice for wiring within a boathouse. The current approach (NM 12/2 with NM staples) means a lot of rust do to the use of the staples. Is there a preferred approach? Sep 9, 2023 at 23:49

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Anytime someone has bonkers energy delivery requirements to dockside, my first thought is "off-grid solar".

Usually the fly in the ointment is the boat lift. It's a big demanding load that pulls thousands of watts for hours. Wait, hours? No, it's seconds. It's a big impulse of energy but it isn't for very long. When you actually look at it in watt-hours, it's very small. So, very much like gates, boat lifts lend themselves well to solar+battery. If an AC boat lift is chosen, the inverter needs to be quite large and will have large standby losses, but it can be switched off when not actively hoisting boats.

Often many of the remaining loads can run straight off DC. I know of several successful "lighting and Internet" setups that are entirely solar/battery.

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