10 gauge 15A breaker?

[machsnell]

I have some old 10 gauge 3 wire that was run to an outside pool pump. No more pump and not going outside.

Can I tap into it and run 14 UF to outside lights and put it on a 15A breaker?

So I would have 10ga coming out of the panel to 14 ga in jb. One leg switched to lights and the other leg to outlet (15A). Share neutral and ground.

This kosher?

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[xyster101]

Yes you can under code, but there are good reasons that you might not want to. Google search 3-wire circuit and do some reading.

What are the "good" reasons not to?

You can use each hot on it's own circuit as long as they are alternating voltage (AKA breakers are above and below each other in the panel).

You must always put the breaker size for the smallest wire you are using. That will be 14 awg in your case, so the 15amp breaker is good. You can always put a smaller breaker on wire, never put a larger one.
Make sure to use a proper slice kit to connect the 14 awg to the 10 awg. Either a waterproof box that is accessible or you can get a burial rated splice kit at HD for about $15 to connect the 10 to the 14s.

 

[TRWham]

If you are running a multi-wire branch circuit (MWBC) with the light(s) on one leg and the receptacle on the other, then, yes, you can install a 2 pole 15A circuit breaker (or 2 single poles with a handle tie) and use the existing cable. The fact that the cable is oversized is not a problem.

 

[Norcal]

Might be a good idea but not required to mark, that there are smaller conductors on the circuit so some doofus does not slap a 30A breaker on it in the future, it is a "what if" so take it as that. Otherwise I see no problem.

 

[pattenp]

If this circuit is direct buried depending on the depth (12" to less than 18") it may require GFCI protection at the source. Another issue is if making it a MWBC it will have 240V potential across the hots and must be buried at least 18 inches if in conduit, 24" if direct bury. The 12" direct bury is limited to 120V 20A circuits with GFCI protection from the source.

 

[TRWham]

Is the existing cable 10/3 with ground or 10/2 with ground? If only 3 wires total, it would not work for an MWBC after all. As for the voltage, I was assuming it was already 240V and installed to code. That it is now serving an MWBC should not change any requirements related to line to line voltage.

 

[Norcal]

One thing I did not notice in the original post until now was the part sharing neutral and ground this is not code compliant.

 

[TRWham]

One thing I did not notice in the original post until now was the part sharing neutral and ground this is not code compliant.

I have the same concern. First read it as there would be a separate ground and neutral shared by the 2 legs, but now I am not sure. I don't know why there would have been 4 wires run to the pump, so now think it's only 10/2, so no joy on the MWBC. May be simpler just to keep it together on a single 20A.

 

[sberry]

I think he meant using them as part of a mwbc.

 

[Norcal]

I think he meant using them as part of a mwbc.

Hopefully that is what was meant & that the OP clarifies it.

 

[teamextreme]

Well, I interpreted what he was asking as something different than all of you. I think everyone is thrown off by his use of "3-wire". This is normally considered a romex cable with 2 hots and a neutral, the ground isn't counted. I think he is referring to a 2-wire cable, one hot, one neutral, but he is counting the ground. If I'm right, then he's not talking about a MWBC at all and is just going to attach a normal 120v circuit to a single pole 15A breaker. In which case there's no issue with OP's plan of using the 10awg spliced to 14. The only thing that makes me not certain of this is he says "one leg here" and "one leg there", implying 2 circuits, but he may just be referring to the circuit being split in 2 directions. We shall see....

 

[machsnell]

Sorry gents out in snow plow action.

It is a 10/3 romex. Red blck neutr and grnd.

It's in the basement and goes to a jb where it splits to 14 uf wire to lights and another 14 uf wire to lights. They are both buried once they leave the basement wall.

My main concern was if it was ok to use the 10 ga wire in a 15A circuit w 15A breaker.

Secondary and not totally needed but would install an outlet or 2 off the unused leg (red).

If I use a tied together 2 pole 15A breaker is it ok or no go?

Yes they share a neutral and ground.

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[TRWham]

The NEC explicitly allows single pole breakers with a handle tie for protection of an MWBC.

 

[pattenp]

What about GFCI protection for the #14 that's buried? Do you know if it buried deep enough not to require GFCI protection?

 

[machsnell]

Got it. Tied together breakers.

Line is buried 12 to 18" and comes up to go up the trees 50 feet.

What does the gfi do for the circuit anyway? I can add pretty easily if better.

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[pattenp]

Got it. Tied together breakers.

Line is buried 12 to 18" and comes up to go up the trees 50 feet.

What does the gfi do for the circuit anyway? I can add pretty easily if better.

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GFI protects anyone from shoving a shovel in the ground and getting a surprise when its buried at 12", but that only applies to 120V 20A circuits or less. Since its on a double breaker the minimum direct bury depth needs to be 24", not 12 to 18". Minimum 18" bury depth is when the wire is run within conduit.

 

[machsnell]

Yeah they are big trees and not possible to get that deep. I will gfi it.

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[pattenp]

GFI breaker does not satisfy the NEC because it's more than 120V. Not sure if you are worried about code or not, but 2" of concrete on top of the wire satisfies NEC depth requirement to only be 6" and no GFI breaker required.

 

[wyliesdiesels]

Yeah they are big trees and not possible to get that deep. I will gfi it.

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a double pole GFCI may cost you an arm and a leg and they do not come in all sizes... what brand of breaker panel do you have?

 

[machsnell]

They are br type breakers.

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[pattenp]

I think BR 20A 2-pole gfci is the smallest and is $90 - $100.