100' 20/30 amp wiring

[Grey Mountain]

New neighbor wants help in wiring an outbuilding primarily for lights. 100' run.
There is a breaker box on the feed pole with empty slots. Appreciate some real electricians keeping me out of trouble here.
This is my plan:

1. Use 12/2 Romex for a 20amp circuit. If he thinks he may need 30 amp in the future, I'll talk with him about 10/2 Romex.
2. Bury the cable in 3/4" or 1" PVC, 18" down.
3. Use 20 or 30 amp breaker at the pole, depending on what his plans are.
4. Simple on/off main switch in the outbuilding with two or three outlets. First outlet would be GCFI protected, next one or two would run from that.
5. Ground wire at the breaker box, then normal grounding in the outlets in the outbuilding.

OK. Whaddya think?

When it comes to 'lectricity, I'm a pretty good wood turner.

GM

[TDKPE]

New neighbor wants help in wiring an outbuilding primarily for lights.  100' run.
There is a breaker box on the feed pole with empty slots.  Appreciate some real electricians keeping me out of trouble here.
This is my plan:

1.  Use 12/2 Romex for a 20amp circuit.  If he thinks he may need 30 amp in the future, I'll talk with him about 10/2 Romex.
You can't put 15 or 20A receptacles on a 30A circuit.  If he wants 30A to the building, he needs a small subpanel with 15 or 20A breaker(s).  

2.  Bury the cable in 3/4" or 1" PVC, 18" down.
NM cable is not rated for wet environments, and underground conduit is considered wet.  They usually fill with water, by the way, sooner or later, so it's definitely a wet environment.  He needs THWN or THHN/THWN conductors in conduit, or run UF cable (direct bury).  

3.  Use 20 or 30 amp breaker at the pole, depending on what his plans are.
No problem there.  

4.  Simple on/off main switch in the outbuilding with two or three outlets.  First outlet would be GCFI protected, next one or two would run from that.
If using more than one circuit in the building, you can use either a main breaker in the subpanel, or just shut off individual breakers.

5.  Ground wire at the breaker box, then normal grounding in the outlets in the outbuilding. 
For 120V only, two current carrying conductors plus a separate equipment grounding conductor is required.  Neutral NOT tied to the equipment ground, but a grounding electrode system IS required.  That's with more than one circuit.  Only one circuit TO the building is allowed, and if it's 15 or 20A, no ground rods required.  If you put a panel on that one circuit, it's a feeder, and ground rods are required.

OK.  Whaddya think?

When it comes to 'lectricity, I'm a pretty good wood turner.

GM

That's all from memory, so hopefully I haven't given any bad info.  

[Grey Mountain]

OK. Thanks. So easy even a Wagon Burner can do it.

GM

[srv52761]

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That's all from memory, so hopefully I haven't given any bad info.  

Sounds right to me.  He does have some options.  If he goes uf the choice is direct bury at 24” or run in conduit at 18”

To direct bury the conductors at 12” it will need to be gfci protected before he buries it.  So he would probably need a gfci breaker or put in a gfi convenience receptacle at the feeder pole, and run it from there.

As you mentioned, code only allows one 15 or 20 amp circuit to be run to a garage or shed before moving to a feeder and sub panel with the required ground system and now an exterior disconnect; but there is an “exception”.  A multi-wire branch circuit is considered one circuit.  So you could get two 20 amp circuits, or 40 amps total power.  You could get a 240 gfi circuit breaker and direct bury with uf, or run uf in conduit and split immediately into two gfi receptacles.
You should use a 240 breaker regardless.  The breakers should be adjacent and they need to be tied together so if one trips, they both trip.
(edit: this is not really an exception, it is a consequence of defining a mwbc as one circuit.)

[TDKPE]

A multi-wire branch circuit is considered one circuit.  So you could get two 20 amp circuits, or 40 amps total power. 

Forgot about that.  Quite right.  And a good option for the OP's neighbor as it eliminates the subpanel and I think the grounding electrode system if there aren't any other metallic pathways between buildings.

[srv52761]

Forgot about that.  Quite right.  And a good option for the OP's neighbor as it eliminates the subpanel and I think the grounding electrode system if there aren't any other metallic pathways between buildings.

Was just on Menards web site . 100’ of UF 12-2 with ground is $60.  100’ of 12-3 wg is $63.  For $3 it wouldn’t even be a decision.

   

   

[Snipe Hunter]

New neighbor wants help in wiring an outbuilding primarily for lights.  100' run.
There is a breaker box on the feed pole with empty slots.  Appreciate some real electricians keeping me out of trouble here.
This is my plan:

1.  Use 12/2 Romex for a 20amp circuit.  If he thinks he may need 30 amp in the future, I'll talk with him about 10/2 Romex.
2.  Bury the cable in 3/4" or 1" PVC, 18" down.
3.  Use 20 or 30 amp breaker at the pole, depending on what his plans are.
4.  Simple on/off main switch in the outbuilding with two or three outlets.  First outlet would be GCFI protected, next one or two would run from that.
5.  Ground wire at the breaker box, then normal grounding in the outlets in the outbuilding.

OK.  Whaddya think?

When it comes to 'lectricity, I'm a pretty good wood turner.

GM

Pretty sure there's a new sigline in there somewhere

[Grey Mountain]

Pretty sure there's a new sigline in there somewhere

I'm good at making square things round and straight hair curly.


GM

[rwe2156]

I agree I'd run 12/3 and give the option for 2 circuits. My electrician says 2 circuits can share a neutral.

[TDKPE]

I agree I'd run 12/3 and give the option for 2 circuits.  My electrician says 2 circuits can share a neutral.

Yes, as long as they're on adjacent breakers so that one hot leg is on L1 and the other on L2.  It's called a multi-wire branch circuit (MWBC), and it's what srv52761 was referring to a few posts up.  That way, the neutral only carries the difference in current between the two hots.  

But the two breakers must have a handle tie, or you can use a 2-pole breaker (NOT half-height breakers, though, unless it's a quad configured for 240V), so in either case flipping one off opens the other.  In the case of 240V on a single strap or to a load, then the 2-pole breaker is a requirement; otherwise, a handle tie is legal.  For a job like this, I'd just use the two-pole breaker, since I'd have to buy listed handle ties which are specific to the make/model of breakers you're using.

If the two hots are on the same phase bus in the panel, the neutral would carry the sum of the current on the two hots, and that's going to overload the neutral, potentially by a lot.  

The service to your house and any 120/240V subpanels are essentially the same as far as the neutral carrying only the current difference, by the way.