Stringing an overhead wire to shed

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  #1  
Old 11-22-10, 02:18 PM
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Stringing an overhead wire to shed

I have a shed about 100 ft from our home and need to run electrical to it. Because of the topography etc. it's not simple to run underground wiring with conduit.

I need at least (1) 20Amp and (1) 15Amp run out there... my electrical box is straight below the pole heading to the house roof where the main comes in. Can I run my wiring to the shed up that pole and string it through the air (overhead) to the shed? If so, do I run something other than outdoor rated wire (12/2 for 120) and, if I do, what do I use to tie it in at the shed side? I was hoping to avoid putting in another box there... but I suppose I could.

Thanks for any advice,
RamseyFilm
 
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Old 11-22-10, 02:58 PM
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need at least (1) 20Amp and (1) 15Amp run out there...
Would suggest a 20a multiwire circuit. That would give you two 20a circuits without needing a subpanel.
my electrical box is straight below the pole heading to the house roof where the main comes in
Do you mean the mast, the conduit that carries the incoming wires to the meter? If so not inside it. Best to run a mast and weather head for the outbuilding. You can use 12-3 or 10-3 UF if it is rated for UV exposure,. Check the jacket of the UF. to see if it is UV rated You need to run at leas a 1/8" steel cable (messenger) to support the UF. The steel cable will need to be grounded to the circuit. You will need multiple support poles for that long a run.

100 feet is about the limit for #12 depending on actual load. I suggest #10. If at a later date you need 240v it could easily be used to supply a 30a subpanel. At the shed you will need a main disconnect and receptacles must be GFCI protected.

At the house you would use a 20a 240v breaker.

You could use Triplex for 120v but the smallest available size would probably be much larger then you need.
 
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Old 11-22-10, 03:23 PM
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The aerial feeder to the shed cannot use the same mast as the incoming service drop from the power company. You will have to install another mast for the shed feeder, or if your house is tall enough you may be able to just mount an insulator to some high framing. What type of area is the feeder to the shed going to be hanging over? How tall is the house and shed?

If you need to erect a new mast, your local power company rules will probably specify how far it should be from the service mast.
 
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Old 11-22-10, 03:28 PM
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Follow-up

"Do you mean the mast, the conduit that carries the incoming wires to the meter?"

Yep, exactly. THANK YOU. This makes sense. I really appreciate your thorough response!

So a 20a multiwire can carry the equivelant of (2) 12/2 (I'm only used to wiring inside - this is new to me)? Adding more support poles is not much of an option. At that point, I probably will go back to burying (assuming I can get to this before our ground freezes this week!). Hmmm... And yes, #10 would be a better option. The shed is becoming my wood shop... so lots of pull, but only one machine at a time and the 15A or second 20A was simply a run for lights/chargers/etc; The other 20a is for a table saw, chop, etc. Only thing I could see is that someday I suppose I might want to put in a small baseboard and insulate the shop... we're at 7200', so it gets pretty cold. But right now I'm not planning on doing that. So I don't want to go too far overboard any more than I want to regret not running something now instead of later. Know what I mean?

I only need one GFCI at the front of the circuit though, right? Oh, and at the house my panel is full so I was planning on putting in (2) piggyback dual 20a (not sure if that's the right name, but two 20s in one breaker) in place of (2) of the singles currently in there.

Again, thanks for your help!
RamseyFilm
 
  #5  
Old 11-22-10, 03:41 PM
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"What type of area is the feeder to the shed going to be hanging over? How tall is the house and shed?"

The house at the top of the mast and the shed where I would want to bring it in are at about the same height - roughly a story above grade... it would fly over a large, undeveloped hillside with no trees.

But it sounds like this is more than I wanted to get into. Back to tearing out stairs, etc. for burial, I suppose.

Thanks for your advice!
 
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Old 11-22-10, 03:57 PM
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There may be other options for burial such as running through the home's basement/crawlspace/attic to an exit point that is easier to trench up to.

If you do go aerial, the cable can be no closer to the ground than 10' going over unused residential land. If there is any vehicle traffic (driveway, turn-around area) the minimum height is 12'. You could probably meet this clearance from the peak of one of the gable ends of a ranch to a similar height outbuilding without erecting a mast. You could do 100' in a single span. If you do erect a mast, you wouldn't want to be any smaller than 2" RMC or IMC (threaded steel conduit). The code doesn't specifically list structural requirements for masts of this type, but I'm going by the rules-of-thumb I would use for a similar sized service mast.
 
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Old 11-22-10, 04:25 PM
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Oh, and at the house my panel is full so I was planning on putting in (2) piggyback dual 20a (not sure if that's the right name, but two 20s in one breaker) in place of (2) of the singles currently in there.
To do a multi-wire you need a 2 pole 240v breaker. They may not make a half size 2 pole beaker for your panel. Further you panel may not be certified to take half size or tandem breakers or may already have the maximum permuted. Post the manufacturer and model number and one of the pros can probably answer that question.
The shed is becoming my wood shop... so lots of pull, but only one machine at a time and the 15A or second 20A was simply a run for lights/chargers/etc; The other 20a is for a table saw, chop, etc. Only thing I could see is that someday I suppose I might want to put in a small baseboard and insulate the shop.
Sounding more like you may want to use the smallest quadplex you can find if you go aerial all the way. I'm guessing that would be #6. The pros can tell you better then I can. That will allow plenty of room for future expansion.
 
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Old 11-22-10, 05:18 PM
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Originally Posted by RamseyFilm View Post
But it sounds like this is more than I wanted to get into. Back to tearing out stairs, etc. for burial, I suppose.
If you do end up trenching, try to find a continuous length of HDPE duct sized for the largest feeder you would want. Check with an underground utility contractor or a supply house to see if they have a reel end to give you or sell to you. You bury the HDPE and pull the conductors later. Then you can just pull in what you need now and defer the added cost of larger conductors until later, or never. Also if you're trenching consider low-voltage needs at the same time, such as Cat 5 for telephone or coax for cable TV.
 
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