Sub Panel in boathouse and Aluminum Feed

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Old 04-02-19, 01:40 PM
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Sub Panel in boathouse and Aluminum Feed

I plan on running power to my boathouse. The boathouse is about 200' away from the main house.

I was looking at 6-3 w/g uf-b copper, which isn't cheap, with 40 amp protection. I have a 6 slot sub panel in the boathouse. Which is wired to some lights and the boat lift that draws about 12 Amps. I plan on direct burial 24" deep and using conduit the last 25 ft for added protection. This is mainly because the boathouse is so close to water and the ground leading up to the boat house at time can be submerged during the rainy season and the lake rises. Note, the boathouse is fixed structure above the water. No part of it floats...

I found Aluminum quadruplex 4-4-4-4 for about a third of the cost of copper and was considering using this. After reading up on aluminum wire and its history, it appears it would be suitable for this type use.
My question is this. Have I missed anything here? Will this work ok for me or did I overlook something? Any suggestions about it's use would be appreciated

Also, I'll be getting a friend of mine who's a certified electrician to look over and help a little with this project. I'm just trying to get all the materials beforehand.

Thanks
 
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Old 04-02-19, 02:01 PM
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To be exact I was looking at Tulsa 4-4-4-4 Quadruplex Aluminum URD Direct Burial Cable 600V Wire...
 
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Old 04-02-19, 02:08 PM
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Mobile home cable is similar but has the advantage of being able to enter the building. URD is not rated for interior use.
 
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Old 04-02-19, 02:51 PM
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I'm a little confused. I would be running this from the outside house panel to the dock/boat house. Yes the sub-panel for the dock is inside a utility room but this isn't consider a dwelling or living structure. Does that matter?
 
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Old 04-02-19, 02:51 PM
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If this wire enters the structure then you need aluminum wire that carries a USE-2/RHH/RHW-2 rating. It is direct bury. Mobile Home Feeder carries those ratings but is a preassembled cable and comes in limited sizes. To get #4 you'll need to buy an individual conductor of USE-2/RHH/RHW-2 and make up the four conductors.

The NEC says USE only rated wire is to be terminated on the outside of a structure. URD which is USE-2 rating has no fire resistance rating.
 
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Old 04-02-19, 03:40 PM
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OK, what about running the aluminum 4-4-4-4 to the outside of the dock and stopping it there. Then do a short run 6-3 w/g uf-b copper to the inside panel. this would still be a lot cheaper. The next question would be what could I use to splice the two together that's watertight? Or is this even an option?
 
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Old 04-02-19, 04:08 PM
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The splice must be in a water proof box. Actual splice could be made with split bolts rated for both copper and aluminum.
 
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Old 04-03-19, 06:16 AM
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My recommendation if you use the URD would be to terminate it in an air conditioner disconnect box (~10$) on the side of the boat house. Run your conduit up from the bottom of the trench to a couple feet above the water line / grade on the building exterior wall. Mount the AC disco box and terminate the conduit there. You can then drill through the wall lined up with a knock out on the back of that box and exit into the building wall using #6 copper NM. You'll only need to buy one copper-to-aluminum splice connector for the neutral as the hots and the ground will terminate on the blocks in the disco. There are a variety of connectors that can do the job, example brands are Polaris and Ilsco, just make sure it's rated for both copper and aluminum in the right sizes.

This also assumes your house panel is on the exterior of the building, and the conduit will be going directly into the ground from the panel.
 
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Old 04-03-19, 08:37 AM
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thanks!

Everyone, thanks for you input. I got a good idea of what I need to do now.
 
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Old 04-03-19, 10:57 AM
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I didn't see this mentioned, but you had said 40 amp protection and #4 conductors will not fit in the lugs of a 40 amp breaker.
 
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Old 04-03-19, 01:05 PM
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40A breaker should take larger than a #4. As an example I believe the 40A Square-D will take up to a #2.
 
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Old 04-04-19, 08:58 AM
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My mistake, yes, both HOM240 and QO240 will accept up to a #2 conductor.
 
 

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