Adding an aditional outlet outside question

BCULP2

Right now I have a receptacle located outside next to a dock about 100' away from the house. Recently I had an addition to the dock and now need power near the other side.

The new receptacle would be about 50-75 feet from the existing outlet. The wire going to the existing outlet is 12g. Would it be too long of a run if I spliced into the existing box with the new one or should I try to run a new line to the house? The only things on this circuit are a few outdoor receptacles and a small light.

Also, I plan to run the new wire underground in PVC conduit. Does anyone know the required depth to burry it in Illinois?

Thanks.

Sparky Joe

Bury your conduit 3 feet unless it's under concrete then you can go less.

Pull #10 wire to your new outlet, that will help the total resistance of the overall run to that new outlet. If you do re-do all the wire then do it all in #10 because of the lengths.

Speedy Petey

"A few outdoor receptacles and a small light" don't really tell us much. It's what you will plug into the receptacles that matters. At that distance try to plug in a "little" 15a circular saw and see how it reacts.

I see no benefit in extending a #12 wired circuit with #10. I do agree that your best bet would be to re-run the existing circuit with #10 and use it to extend to the new loads. I would also run a multi-wire circuit (shared neutral) to lessen voltage drop. Keep one circuit at the old area and the other circuit to the new area.


Also, in 99.9% of the country PVC can be burried @ 18", without concrete.

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Sparky Joe

I assume you know how to calculate voltage drop and that it's inversely proportional to circular mils. Of course it would be better to start the circuit with #10 and then drop down in size as you drop a few outlets. But mathematically there is a benefit to upsizing later in the run, and also the benefit of not having to re-wire the whole system.

BCULP2

Thanks so far.

Mostly it will be just the battery charger for a boat.

I did a little searching online and it looks like it I were to use a metal conduit then the depth wouldn't have to be as deep, but I can't find an exact depth required. Anyone know about this? I really dont want to have to dig down that deep.

Speedy Petey

I truly don't think you want to mess with rigid conduit for this run.
Under the NEC the minimum cover depth for PVC is 18", unless it is under a roadway, then it's 24". Under 2" of concrete is 12". Under 4" of concrete with no vehicular traffic is 4".
There is no cover depth greater than 24" in the NEC regardless of conduit type.

The difference in using #10 as opposed to #12 for the extra 50' is .8 volts @ 10 amps. IMO it's not worth it for the light load this circuit will see.
To each his own.

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Sparky Joe

So i guess you do see there is a difference? and what 'K' do you use for copper? (can't remember isn't it 12.something?)

By your math for the total run you'd have a 2.8 drop and that's with the benfit of only 10 amps while it's clearly capable of 20.

By figuring with what its capable of you're at 5.6 which is well over the NEC fpn of 3%

Speedy Petey

With the existing #12 he is already over 3%, so another .8v drop with not be noticed IMO.

It ALL depends on the actual load. I stated my opinion which is to re-wire the circuit. I'll stick with that.

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Sometimes I feel like if I answer any more questions it is like someone trying to climb over a fence to jump off a bridge and me giving them a boost.

RobertWilber

Table 300.5; column 4: 12" for 120 volt residential circuit with GFI protection - 20 amp protection - direct burial

Sparky Joe

Good point, if something is already a pile of crap, why bother doing it right. Unless in the future you plan to re-do the poorly done portion.

And IMO 12 or 18 inches is too shallow for my backyard, so I wouldn't do it somewhere else.

Speedy Petey

Your personal opinion is NOT necessarily the code now is it? Let's stick with code facts first. Opinion can come later.



Very true Robert. I neglected to add that column. Remember it needs to be GFI protected ahead of the under ground portion.

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Sometimes I feel like if I answer any more questions it is like someone trying to climb over a fence to jump off a bridge and me giving them a boost.

BCULP2

I should have posted this to begin with.

The existing outlet is near the stairs. The one I would like to add needs to be past the left side of the picture.

Would running it in conduit underneath the lip on the back side of the top of the wall work? There is already a low voltage line going to the lamps there and would probably be enough room for the conduit too.


Any other ideas?

Sparky Joe

You could attach the conduit to the backside of the retaining wall, and would't have to worry about burying it at all(just enough so you don't see it). If the low voltage is in the way, just move it wherever you like, there's no code on that.

Very nice looking patio too by the way. I apologize for the "pile of crap" comment above, just making a point, it obviously is not.

"IMO it's not worth it for the light load this circuit will see.
To each his own."

I've seen that IMO phrase to many times from you to not be able to use it myself.

I guess code and good practice are two different things. Doesn't say somewhere in article 90, that the code is the minimum?

Speedy Petey

I was more referring to your original post of 36". That was written as fact. Then later you say it was an opinion.
That is all I meant. You are just as entitled to an opinion as me or anyone else.
Don't be so sensitive. :p

__________________
Sometimes I feel like if I answer any more questions it is like someone trying to climb over a fence to jump off a bridge and me giving them a boost.