wiring outbuilding/workshop -need advice

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  #1  
Old 11-21-11, 09:46 AM
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wiring outbuilding/workshop -need advice

i want to run power to my new outbuilding/workshop from my homes 200amp service box,building is 190feet from main service box.i need 8 outlets-1 gfci - 2 switch/outlets for my 2- 4' floresent lights and 5 wall outlets.i will sometimes be using a small 110 ac and a 110 welder 90amp , also small power tools- but one at a time, what size breaker at house , uf wire size house to workshop,wire size inside workshop,i would like to keep simple and low cost as possible,i also have a 60amp breaker box at pool for pump is it possible to run uf to workshop from this box ? thanks
 
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  #2  
Old 11-21-11, 09:51 AM
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The cheapest way that will meet your present need, but leave no room for expansion, would be to install a 20A multiwire circuit. You would run 10-3/g UF-B cable, buried 24" deep from a double-pole 20A breaker in your main panel. At the outbuilding you would need a two-pole disconnect switch and two GFCI receptacles (all receptacles must be GFCI protected in a workshop). This would give you the equivalent of two 20A circuits at the workshop, approximately 4800 watts of power.

If you want more power or room for expansion, you would need to install a subpanel.

It would be best to run from the main panel and not the pool panel. The pool panel is probably designed to just have the power the pool equipment requires.
 
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Old 11-21-11, 11:50 AM
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could you give me more info on the 2 pole disconnect switch -amp ect.for 20a multiwire circuit,and wire size inside workshop thanks
 
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Old 11-21-11, 12:03 PM
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The simplest way to do a disconnect is probably to use an unfused air conditioner disconnect. It's about $10. This should be right where the feeder cable enters the building -- it is a building disconnect.

Inside the workshop you can wire two 20A circuits using 12-2/g NM-B cable where the cable will be protected from damage -- inside sheathed wall cavities, in the ceiling. If the wiring is exposed or otherwise subject to damage then you need to use protection like conduit or install substantial running boards to protect the cables. Many inspectors will allow MC (metallic cable) or AC (armored cable) in lieu of conduit in a residential workshop, although it is not strictly allowed to do so in the code.
 
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Old 11-21-11, 12:21 PM
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thanks,this is how i want to go with it- let me get to digging!
 
  #6  
Old 11-28-11, 02:48 PM
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advice on wiring 20amp multiwire circuit to outbuilding/workshop

1-using 10/3 uf need info on wiring 20amp breaker at main panal - 2-how to wire 10/3 at unfused 2 pole disconnect in building - 3-how to wire each 20 amp circuit out of disconnect -i want 4 outlets on each circuit- first outlet each side gfi thanks
 
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Old 11-28-11, 04:01 PM
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Originally Posted by bb2468 View Post
1-using 10/3 uf need info on wiring 20amp breaker at main panal - 2-how to wire 10/3 at unfused 2 pole disconnect in building - 3-how to wire each 20 amp circuit out of disconnect -i want 4 outlets on each circuit- first outlet each side gfi thanks
First you may want to pick up a book such as Wiring Simplified at Home Depot, Amazon, or other places. You need the basics and reading is a good way to learn. Then you can come back here and ask specific questions about anything you don't understand.
 
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Old 11-28-11, 06:14 PM
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have 2 books, nothing on multiwire circuits to buildings just wanted to make sure of connections w/10-3 at service panel and disconnect box in building. sorry to have troubled you w/ such basic questions ray2047 thanks ibpooks for your help
 
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Old 11-28-11, 08:03 PM
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A 120v supply is derived from a 240v hot and the neutral. The neutral is the center tap of the secondary of the transformer supplying your house with 240 volts. In a multi wire circuit the two 120v supplies are derived from one of the two hots and the shared neutral. The neutral carries only the differences in amps on the 240 so it only needs to be as large as the 240v wires. For example if you have 10 amps on one 120 circuit and 15 amps on the other 120 the neutral only carries 5 amps. Even if you have 0 amps on one and 20 amps on the other you still only have 20 amps on the neutral.

At the panel black and red to the two poles of the 240v breaker. White to neutral. Ground to ground bar or neutral bar if no separate ground bar.

The two pole disconnect is wired like a 120v switch except both hot wires are interrupted. One hot on each pole. The neutrals are connected together. The grounds in the usual manner. More specifically red to one pole of the disconnect and black to the other pole. Whites wire nutted together. Grounds pigtailed to the grounding lug of the disconnect.

If you are going to use only one GFCI for each circuit you need to split the 12-3 into two circuits before the first GFCI. There are though two other ways to accomplish this. Install a GFCI breaker or using GFCIs for each receptacle.

In method one you use two GFCI receptacles. On the line side the white is pigtailed to both receptacles and red to one receptacle and black to the other. A 12-2 is run from the load side of each GFCI.


That is the basics. I'm not sure how clear I was. Please post back and I will try to explain better.
 

Last edited by ray2047; 11-28-11 at 08:35 PM.
  #10  
Old 12-03-11, 12:07 PM
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Wiring my garage

My garage is about 90 feet from my main circuit breaker panel. I have already buried 55 feet of #10/3+ground in anticipation of future need. As yet I have just connected a 20A 120v circuit and capped off the extra wire.

Now I want to maximize my power to connect a new table saw with a 220v 3HP motor, and be ready to charge an electric car, someday. I have a LOT of questions. Please let me start.

10 gauge wire should allow me to use a 30A breaker, but, my understanding is that at 100 feet, because of voltage drop, I'd need to drop down to a 20A cb, so I am on the cusp.

My first question is whether I can run a #8 cable for that first 30 feet, within my home (before it connects to the underground cable outside) and have a direct connection still with a 20A breaker in keeping with the NEC.

But, I really think a better alternative would be to place a sub panel at the end of that 30 foot run of #8. That would leave me with only a 55 foot run of #10. Would that allow me to use a 30A breaker in the main panel?

But it seems that I would still need to install another sub panel where the cable enters the garage (can I have a junction box before that panel?) so that I can use a 30A breaker (do I need a switch disconnect box) for the saw, and use a 20A breaker for outlets and lighting, etc.

Is my logic sound?
(more later)

Carl
 
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Old 12-03-11, 01:06 PM
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If you are looking to recharge an electric car and also run sizable electric motors like your saw has, I think you should consider a larger capacity sub-panel in your garage. What are the current demands for an electric car charger now?

You don't want to spend the money on all that copper now and then find out a few years form now you need to replace it with something larger. Copper will only get more expensive.

You can install a disconnect for your table saw or use a twist lock plug. I put plugs on all my machines for my shop.
 
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Old 12-03-11, 01:48 PM
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As I see it, now, the 30A would probably be useful, although, admittedly, 40-50A would be better. But in terms of money spent on copper, the underground cable is already there. Installing 30 feet of #8 in the house is not the weak link.

On the other hand, I plan on using a disconnect for the saw, and I don't expect to run the saw and the charger simultaneously.

Thanks
 
  #13  
Old 12-05-11, 11:53 AM
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Thumbs down Price of copper

I was in Home Depot, getting something else, and I checked the price of Romex. 4 conductor 6 gauge costs only 8 cents per foot more than 8 gauge, so I am going to use the higher capacity wire, on that part of the run, anyway. When the employee double-checked the prices for me, they were even lower than the posted prices.
The only remaining question I need to answer is about the boxes I need at each end of the underground run....
 
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Old 12-05-11, 12:37 PM
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I checked the price of Romex. 4 conductor 6 gauge costs only 8 cents per foot more than 8 gauge, so I am going to use the higher capacity wire, on that part of the run,
Do you mean 3-conductor, white, red, black, ground? Romex (NM-b) can't be used outside. Was this for the interior portion of the run?
 
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Old 12-05-11, 01:53 PM
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Post Copperprices

Yes, I meant 8/3+ground, and yes, that is the indoor Porto on of the run. I have no need to dig up and replace the 10/3 I already have buried, but a funny thing happened on the way to Home Depot. I stopped into my local electrical supply shop, just a block away from HD and found that although the price for the 6/3 wasn't soo bad, at 30cents more at HD, the price for the 8/3 was an outrageous 90 cents per foot more at Home Depot. It pays to shop.
 
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Old 12-05-11, 02:53 PM
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The 10-3 will limit you to a 30a breaker at the house but you know that.
 
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