OT: Wiring to boat dock question

[BillGalbraith]

I need to run 12-3 wire (220-volt) 150 feet to my boat dock. It will be completely under a wooden walkway that is slightly raised, enough so that I can get the the cable under it, but cannot tack it up, so it will be lying on the ground. I plan on using UltraTite Liquidtite non-metallic flexible tubing the entire length to protect the wire from critters gnawing at it. The UltraTite will be under the walkway the entire length of run. I will have to use two pieces of Ultratite (100 foot and 50 foot), with a connector. The area can be under water when the lake overflows because of a hurricane or other storm system, so I'll make sure that the connector is as high as possible, and as secure as possible.

My question involves the wire. I believe that I'm NOT supposed to use Romex, because this is considered a wet location, and there is paper around the ground wire. Do I have to use an underground rated wiring, even inside the Ultratite, or can I just buy individual wire (2 pieces of black, one white, one ground) and pull it through that way? There is a surplus store that I should be able to get wire by the foot at a decent price. Otherwise, I have to buy 250' or 500' spools of wire from Homer.

Should I use solid wire (single strand) or stranded wire? I thought I remembered from college Electrical Engineering class a million years ago that a solid wire carried the current better than a stranded wire, but the electrical guy at Home Depot said stranded was better.

Also, is a ground wire required and/or a good idea. Homer's electrical guy said that I could go with a one-size smaller ground wire (14 guage), and said that I really don't even need it, since the neutral is tied to the ground bar at the service. Since this is around water, I think I'd rather play it on the safe side, rvrn if this is never going to be inspected.

Thanks. You guys are a better source of information than Homer, even though I have to put up the public ridicule.

 

[oleguy]

ground should be #12 same as your hots and neutral. liquid tite ok for flexability.also gfci.
solid or stranded what ever you want.#14 is to small.ground wire is always required.

 

[mrb]

wow that is scary advice you got from the guy at home depot. you cannot reduce the size of the ground on 15,20,and 30 amp circuts, and you DO need it. You should complain to the manager.

The wire you propose to use from a surplus store, what type is it?

 

[BillGalbraith]

The wire you propose to use from a surplus store, what type is it?

I haven't been there yet, so I don't know if they will have 12-3 wire, or I'll have to use individual pieces of #12 wire, but at least I'll be able to use one continuous piece. HD price on cut wire was $0.30/ft for #12 wire, making this a $180 job for just the wire. The Ultraflex adds more $$$ (I don't remember the price on that).

One option that I thought of was to make up the 150' with two pieces, 100' and 50', since those are common lengths that I could buy without having too much surplus. I would solder and double heat-shrink seal each connection, like one would do for an underwater pump, but I'd rather do it in continuous runs. One less place to have a problem, and if a problem arises, it would require pulling the whole line out and starting over.

If the surplus store doesn't come through, I'll have to price #12 wire in 250 ft length spools, compared to having it cut at $0.30/ft, and just plan on having lots of excess. I can maybe put it to good use in the new garage wiring outlets.

 

[BillGalbraith]

ground should be #12 same as your hots and neutral. liquid tite ok for flexability.also gfci.
solid or stranded what ever you want.#14 is to small.ground wire is always required.

I thought about the GFCI issue when I fell asleep last night. I'll look into a double-pole GFCI breaker for this.

 

[wbrian63]

you shouldn't splice wire in mid-run unless there's a junction box, even the way you describe it.

Also - I'd check with an electrical supplier for the wire. I recently had to buy 200' of #4 THHN (stranded). Home Depot wanted .88/foot. I got it for about 65% of that price. Also needed #8 in the same length, .44/foot at Home Depot was .29/foot at the supplier.

Stranded is easier to pull than solid.

You should be concerned about voltage drop over a 150' run. Generally, 12 ga is good for 20A, how much draw are you looking at out at the dock? My calculations show possibly a 9.5v drop at 20a over that distance. Lower draw will equal lower drop, of course. Depending on what you're doing, 9v drop may not be significant.

 

[BillGalbraith]

You should be concerned about voltage drop over a 150' run. Generally, 12 ga is good for 20A, how much draw are you looking at out at the dock? My calculations show possibly a 9.5v drop at 20a over that distance. Lower draw will equal lower drop, of course. Depending on what you're doing, 9v drop may not be significant.

I did take into consideration the length of run. I don't remember the maximum draw of the sprinkler pump or boat lift that are on this circuit, but #14 wire would handle it for a shorter run, but I had to go to #12 for the 150' run that I have.

 

[mrb]

NEC prohibits soldered splices like you describe. Splices must be mechanical.

 

[hidollartoys]

I have a lake house on the Lake of the Ozarks in MO. I have a boat dock with 60 amps. When you purchase the wire make sure the designator contains a "W" such as THHW, THWN, THW, RHW or XHHW. Definately use a GFI breaker to feed the circuit and make sure that each individual component or equipment piece is bonded to the ground wire. Also use RNC, LFNC, ENT conduits and associated boxes. DO NOT USE METALIC CONDUITS OR ENCLOSURES!!!! You stated that your walkway was wood. I assume your entire dock is wood. Docks here are steel and pose a set of problems that have caused electrocutions of swimmers. Do all you can to isolate the electrical energy for the dock structure. If your dock is steel you should bond it to a ground rod in case of a lighting strike.

 

[BillGalbraith]

Stop, time is up. Put your pencils down.

I think we've beaten this dead horse enough. I have other issues to solve....

Thanks guys.

 

[nehog]

...
My question involves the wire. I believe that I'm NOT supposed to use Romex, because this is considered a wet location, and there is paper around the ground wire. Do I have to use an underground rated wiring, even inside the Ultratite, or can I just buy individual wire (2 pieces of black, one white, one ground) and pull it through that way? There is a surplus store that I should be able to get wire by the foot at a decent price. Otherwise, I have to buy 250' or 500' spools of wire from Homer.

Any wire rated for direct burial is ok.

Should I use solid wire (single strand) or stranded wire?

Stranded will be easier to work with, and to pull.

I thought I remembered from college Electrical Engineering class a million years ago that a solid wire carried the current better than a stranded wire, but the electrical guy at Home Depot said stranded was better.

I think you remembered it backwards, you are referring to 'skin effect' but in reality that doesn't become a factor until the frequency is much higher than the 60 Hz line frequency. For once, the HD guy was right!

Also, is a ground wire required and/or a good idea. Homer's electrical guy said that I could go with a one-size smaller ground wire (14 guage), and said that I really don't even need it, since the neutral is tied to the ground bar at the service.

OK, take back all I said about him! No! And the same AWG as your other wires.

Since this is around water, I think I'd rather play it on the safe side, rvrn if this is never going to be inspected.

better safe than sorry!

Thanks. You guys are a better source of information than Homer, even though I have to put up the public ridicule.

Use a GFCI breaker (not an outlet unless you put the GFCI outlet at the beginning before the run.)