Electrical hook up to my shed

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  #1  
Old 07-10-02, 05:22 AM
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crawdadcreek
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Electrical hook up to my shed

I need some advice on how to hook up an electrical supply to my shed. The shed is approximately 200 feet away from the house. I have a 20a line from the house that I would like to use because it's already there and it is not being used by anything else. I do not want to bury the cable as it will lay under some decorative brick work. I would also like to have some type of breaker box in the shed. I will be installing a couple 8' flouescent light fixtures and using the shed for some simple wood work and plain pidaling.
1. What type of wire
2. 20a big enough.
3. breaker box???
4. How about a ground. It's a metal 12'x24' shed

I am very much a novice, so even some simple advice to you might be very important to me. Thanks for any help......brian
 
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  #2  
Old 07-10-02, 07:01 PM
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pdesiato
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You have two choices underground (buried) or overhead I would suggest underground it makes for a much neater looking job.

20amps is not enough if you have plans to have some woodworking tools out there. I would install a small sub-panel in the building.

Pat
 
  #3  
Old 07-11-02, 01:03 PM
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Try the following article concerning detached garages. Most if not all of what is said there would apply to a shed. There is drawings showing both underground installation examples and overhead installations. May be of some help to you.

http://www.homewiringandmore.com/hom...detgarage.html

Good Luck

Wg
 
  #4  
Old 07-12-02, 06:38 AM
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Thanks for the info but one more question. Should I use 12/2 or 10/2 wire. I will be threading it through the cheapest water line I can find and burying it several inches in the ground. My shed is 200 feet away from the house. I am also going to install a 110v single pole
arm fuse box in the shed. For now, this will be a 20a circuit.
For just the one 20-amp circuit at 200 feet, I would use 10-gauge wire to avoid excessive voltage drop.

"Several inches" is not deep enough to meet code. I don't have my book with me to tell you exactly what you need, but I'm sure someone else will look that up for you. It varies depending on what kind of surface is above the cable.

You should use electrical conduit, not water pipe. Or in most areas you can simply bury UF cable directly without conduit. But if you use conduit, you'll be happier with individual THWN wire rather than UF cable.

If you install a subpanel, you'll be forced to also install grounding rods. Furthermore, it you plan to add circuits later, you'll may want even larger wire than the 10-gauge. Finally, if you put in the subpanel, I suggest you go add the third insulated wire so that you can get twice as much power through the same gauge wire, with less voltage drop. In this case, you may want 10/3 or 8/3. 10/3 will provide you with more power than 8/2.
 
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Old 07-12-02, 12:03 PM
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Depth of bury and building disconnecting means.

Originally posted by John Nelson
For just the one 20-amp circuit at 200 feet, I would use 10-gauge wire to avoid excessive voltage drop.

"Several inches" is not deep enough to meet code. I don't have my book with me to tell you exactly what you need, but I'm sure someone else will look that up for you. It varies depending on what kind of surface is above the cable.

You should use electrical conduit, not water pipe. Or in most areas you can simply bury UF cable directly without conduit. But if you use conduit, you'll be happier with individual THWN wire rather than UF cable.

If you install a subpanel, you'll be forced to also install grounding rods. Furthermore, it you plan to add circuits later, you'll may want even larger wire than the 10-gauge. Finally, if you put in the subpanel, I suggest you go add the third insulated wire so that you can get twice as much power through the same gauge wire, with less voltage drop. In this case, you may want 10/3 or 8/3. 10/3 will provide you with more power than 8/2.
The absolute minimum depth of bury is six inches for rigid metallic conduit. If you use nonmetallic conduit you will need to have twelve inches of cover and a two inch thick concrete pad over it, or eighteen inches of cover. If you use cables suitable for direct burial you need eighteen inches of cover and two inches of concrete or eighteen inches of cover. You can use any wiring method with one foot of cover if you limit the circuit over current protective device to 20 amperes and provide ground fault protection to the circuit.

Given the distance you will want to run this circuit in conduit. The reason I say this is that if you run it in direct buried cable it is not practicable to upgrade the circuit to a heavier one later. The smart move is to go two foot down and install rigid nonmetallic conduit, then backfill or separate by six inches and install another conduit for communications circuits. If you use conduit then you can change the wiring as your needs change without doing any more digging.

If, however, all you want is twenty amperes out there at the shed and you are sure that your needs will not change in the future then you should install a three wire plus ground cable in which you can run a multiwire branch circuit. For the additional cost of the three wire cable you can have twice the useable current and a lower voltage drop. 10/3 W Ground will give adequate performance for a twenty ampere circuit over that distance but you will need to install a twenty ampere ground fault circuit interrupter breaker to provide the required GFI protection to the buried conductors.

You will need to install a double pole switch in the first junction box just inside the shed were you change from the underground to interior wiring method. This switch is the building disconnecting means. You can use any two pole "snap" switch. It does not have to be listed as service equipment. You can identify the switch by the fact that it has four terminal screws and it has the words on and off on the toggle itself.
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Old 07-12-02, 05:56 PM
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Hatteras
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No offense intended but you sound like too mich of a "novice". You should hire an electrician to do this type of work. If you are getting involved with voltage drop calculations you need a professional. How do you know that 10-3 will be large enough? How do you know the grounding is adequate? You're settinf yourself up for some problems, electrically and legally.
 
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Old 07-13-02, 11:59 AM
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Why not try to help?

Originally posted by Hatteras
No offense intended but you sound like too mich of a "novice". You should hire an electrician to do this type of work. If you are getting involved with voltage drop calculations you need a professional. How do you know that 10-3 will be large enough? How do you know the grounding is adequate? You're settinf yourself up for some problems, electrically and legally.
Hatteras
Are you aware that this is a self help sight? We have two choices in answering the folks who come here looking for help. We can tell them to hire an electrician, they won't; or we can give them careful and complete advice so that the work they do any way will be reasonably safe. On this sight the second approach is what is used. It is called doityourself.com after all.
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  #8  
Old 07-13-02, 04:10 PM
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Well said hornetd, I too am convinced that people are going to do it themselves with or without any suggested information provided to them in the DIY. At least in the DIY they can get our best attempt to help with the seeking knowledge. The DIY is much better than them doing it anyway blind of any increased knowledge.

Wg
 
  #9  
Old 07-14-02, 08:20 AM
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Hatteras
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Re: Why not try to help?

Originally posted by hornetd


Hatteras
Are you aware that this is a self help sight? We have two choices in answering the folks who come here looking for help. We can tell them to hire an electrician, they won't; or we can give them careful and complete advice so that the work they do any way will be reasonably safe. On this sight the second approach is what is used. It is called doityourself.com after all.
--
Tom
Yes - I am aware this is a "do it yourself" site. But some jobs are not do it yourself or should not be attempted by people who have no clue as to what they are doing. We're not talking replacing a switch here. Electrical work is something that can kill you or burn your house down if not done correctly. Case in point. There are people on here whose advice violates the NEC. What happens when somebody gets hurt because they were following advice (no matter how well intentioned)? I have been in the electrical business for 20 years. I have seen the results (sometimes tragic) of do it yourself electrical work.

Hatteras
 
  #10  
Old 07-14-02, 01:00 PM
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crawdadcreek
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First of all I would like to thank everyone for their input. ALL posters have said something very important! To restat my needs, all I really want to do is to get hooked up with a couple of outlets and a light switch the cheapest and easiest and safest way possible. I am a novice and much of what has been posted I do not understand, but I also think some of the advice leads to something more technical than what I am after. Can I safely run a burial type cable (buried 6") 200 feet to a 110v fuse box with a couple of outlets and a light swith?
Thanks again......brian
 
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Old 07-14-02, 01:15 PM
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Re: Re: Why not try to help?

Originally posted by Hatteras

Yes - I am aware this is a "do it yourself" site. But some jobs are not do it yourself or should not be attempted by people who have no clue as to what they are doing. We're not talking replacing a switch here. Electrical work is something that can kill you or burn your house down if not done correctly. Case in point. There are people on here whose advice violates the NEC. What happens when somebody gets hurt because they were following advice (no matter how well intentioned)? I have been in the electrical business for 20 years. I have seen the results (sometimes tragic) of do it yourself electrical work.

Hatteras
Are you saying that wiring the feeder to a shed is a job no doityourself type should tackle? Each of us is only responsible for the advice we give. If you spot advice that you believe violates the NEC you should point that out. Attempting to deter people from working on their own homes is a fruitless enterprise. If you do not feel that the person asking the question is incapable of understanding the advice you might give then advise him/her were to get a good home electrical manual. My favorite one happens to be Richter and Swans "Wiring Simplified". Reconcile yourself to the fact that the work will proceed with or without your help and give the most appropriate advice you can. Just recognize that the hire a pro mantra does not go over well in a DIY forum.
--
Tom
 
  #12  
Old 07-14-02, 01:52 PM
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crawdadcreek,

I think we can look past this side discussion going on and continue working on your problem. A lot of people are trying to cover all your options, but you only need one cheap/easy/safe way (everybody here wants to future-proof this against a large increase in power demand, but you have indicated no such need or desire). The cheap/easy/safe way does not involve a subpanel, and I will not be providing subpanel information because it is unwise and unnecessary.

Here's your shopping list:[list=1][*]Enough 10/2 UF cable to reach from your panel to your shed -- the 200 feet you mentioned. I'm going to assume that your typical usage will not exceed about 14 amps (even though we're going to use a 20-amp breaker). Occasional usage above 14 amps is okay as long as it's not common or for a long duration. Otherwise, the voltage drop over that distance will be excessive. Excessive voltage drop is a little bit hard on your motor-driven tools, but it's not unsafe unless a continuous condition (your motors could overheat). Anyway, I think the 10-gauge is a reasonable compromise given your desire to do this cheaply (besides, once you get into 8-gauge, the connections become more difficult).[*]100 to 250 feet of 12/2 NM-B cable.[*]A GFCI receptacle (15-amp with 20-amp pass-through).[*]A 20-amp 120-volt single-pole breaker that is of the manufacturer and model for your panel.[*]A supply of wire nuts.[*]A collection of boxes. I recommend the 22.5 cubic inch plastic ones.[*]A collection of red and yellow wire nuts.[*]Switches and receptacles. You can buy ones rated for 20 amps, but you don't need to -- 15-amp switches and receptacles are fine.[*]One 10-foot section of 1-inch PVC conduit.[*]Any tools you need.[*]Rent a trencher.[/list=1]Now here's what to do.
  • Get a building permit.
  • Dig a trench from the house to the shed. The trench must be a minimum of 12-inches deep. Six inches is not deep enough.
  • Lay out the cable in the trench and slip some of the conduit over each end to protect the cable as it emerges from the ground and to the bottom of the trench.
  • Partially cover the cable to hold it into place (save the final cover until you've tested everything).
  • At the house end, install a box and the GFCI receptacle between the panel and the trench.
  • Run the cable from the trench into this box, and connect it to the "load" side of the GFCI.
  • Finish wiring your shed for lights and receptacles with 12/2 cable.
  • Run more of the 10/2 UF between the GFCI and the panel. At the GFCI, connect this to the "line" side.
  • Consider having an electrician install the breaker and make the connections to the panel. This can be dangerous, and there are a lot of codes involved about how the cable is secured, routed and connected.
Obviously you need to know a ton more than this. Read several good books on home wiring before you start. Post back with any specific questions as you go along. If you have any doubts or do not fully understand what you are doing and the applicable codes, stop and consider calling a pro.
 
  #13  
Old 07-14-02, 01:54 PM
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crawdadcreek, There is a wide variety of means to do as you wish. Most often you type job is done underground rather than overhead. The trench is a pain but not normally as much of a pain to install a steel supported cable in the air that much distance.

If I were doing this job as you discribe I would buy 10/3wGrnd UF cable. Run the cable from your main panel using the larger wire to cover any voltage drop concerns due to the 200 feet reaching out close to your limits and still have suitable power avaialble when you get there.

I would poke a hole in the back of your house main service panel using a 1" nipple to get outside the house. Then I would install an LB so the conduit will lay flat to your outside wall and another piece of conduit to run into the ground. Dig a trench 18" deep to the decrative sidwalk you have. Then dig a trench on the other side of the side walk you have going to the shed. Then drive a 1 1/2" rigid conduit from the one trench through the dirt under you sidewalk into the second trench. This way you don't have to disturb your existing side walk. Then fish the wire through that conduit sleeve from one trench into the second trench then going to the shed. Then at the shed use a 1" conduit coming out of the ground to another LB then another nipple going through the shed wall into your panel. The panel must have a ground rod and a grounding electrode conductor connected to that panel in that shed. In the house install a 30 amp 240 volt double pole breaker connecting the red and black wire of the 10/3wGrnd cable to the two lugs of that 30 amp breaker. Then connect the white wire to the neutral bar of you house panel and the bare wire to the grounding bar of the panel in your house. IN the shed connect the red and black wire to your main lugs of your panel main breaker and the white wire to the neutral bar of the panel. Make sure the neutral bar is isolated from the grounding bar and hte metal case of the panel in the shed. Connect your bare wire of your feeder and the grounding electrode condcutor from your ground rod to the grounding bar of that shed panel and bond that grounding bar to the metal case fo the panel but again isolate this grounding bar from the neutal bar of that shed panel.

This will give you 220 volts 30 amps to your shed which should solve any voltage drop concerns and give you enough power to do most common activities in a shed or small garage.

Hope this helps

Wg
 
  #14  
Old 07-14-02, 02:05 PM
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Haterris, I understand your concerns and personal feeling. Problem is Hornetd is right about do it your selfers. Wether it is legal or not they will do it themselves. Most often this doityourself activity is more expensive than if they had hired a qualified electrician, but they do learn themselves as they do the job.

I am wondering if you truly have concerns for the do it yourselfer's safety or concerns that electricians are losing electrical work because of sites like the DIY helping those help themselves.

It is really a self survival subject. Most people do their own work whether it be working on a car to wiring their home.

While I believe this is Americal and we should promote the freedom of choice espectially in a person own personal home, I do believe that if you are doing eletrical work for hire you should have been tested and have proof of knowledge in what you are higing out to do when it concerns electricity.

What reaises my question as to what your true reason for posting you warnings to call an electrician is that you just say the word electrician. You have no mention of confirming proof of knowledge of that electrictian though. Why is that part left out.

What makes an electricain? In your opinion any person calling themselves electricians and hiring out to do electrical work make that person an electrician.

If a person spends his or her time reading all that has been offered in the DIY they may be better skilled as an electrician that one they may hire locally.

Why do you just advise hiring and electrician instead of saying an electrician that can show proof of having passed a nationally recognized testing sytem's test? Is it possible that you are feeling that electricians are losing avaialble work because of the DIYers?

Just curious

Wg
 
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Old 07-14-02, 04:32 PM
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Hatteras
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Originally posted by Wgoodrich
Haterris, I understand your concerns and personal feeling. Problem is Hornetd is right about do it your selfers. Wether it is legal or not they will do it themselves. Most often this doityourself activity is more expensive than if they had hired a qualified electrician, but they do learn themselves as they do the job.

I am wondering if you truly have concerns for the do it yourselfer's safety or concerns that electricians are losing electrical work because of sites like the DIY helping those help themselves.

It is really a self survival subject. Most people do their own work whether it be working on a car to wiring their home.

While I believe this is Americal and we should promote the freedom of choice espectially in a person own personal home, I do believe that if you are doing eletrical work for hire you should have been tested and have proof of knowledge in what you are higing out to do when it concerns electricity.

What reaises my question as to what your true reason for posting you warnings to call an electrician is that you just say the word electrician. You have no mention of confirming proof of knowledge of that electrictian though. Why is that part left out.

What makes an electricain? In your opinion any person calling themselves electricians and hiring out to do electrical work make that person an electrician.

If a person spends his or her time reading all that has been offered in the DIY they may be better skilled as an electrician that one they may hire locally.

Why do you just advise hiring and electrician instead of saying an electrician that can show proof of having passed a nationally recognized testing sytem's test? Is it possible that you are feeling that electricians are losing avaialble work because of the DIYers?

Just curious

Wg
My concern is not for any electricians losing residential work. My concern after reading some of the questions posed here is for the safety of the people asking the questions. I understand too that pwople will do what they want. But when they do not know what they are doing they're going to get into trouble at some point. I was called to a house fire one night that was caused by faulty electrical work. I got there just as they were removing the body bags containing 3 little kids. I was a troubleman for the local utility rsponding to that call that was caused by a DIYer that had no business wiring anything.

As far as proof of qualifications, anybody who hires an "electrican" without checking credentials is foolish. You're right, anybody can call themselves an electrician. To work as an electrician you either must have a license or work for a contractor who does. And to consider yourself an electrician you must have the required training and experience.

I don't recommend calling an electrician for every job I read about here. I believe that alot of electrical work can be completed safely by the homeowner. Start asking about proper grounding, wire and circuit sizing of feeders though and maybe you're in over your head.

If an electrician has been through the requried training and has the experience to pass local and state qualifying exams, somebody reading advice here is not going to be more qualified.

Worried about some electricains losing work to DIYers? No.

Hatteras
 
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Old 07-14-02, 05:55 PM
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I read a test in a farm magazine about electric upgrades. Out of 14 the only 2 that passed inspection were the owner projects. Due to the cost many little details get skipped by contractors and once a job is bid,,, well,,,, the faster we done the better. Also,, like my case I am going back and correcting errors that wouldnt get fixed if one had to hire it done,or ignoring it because its pre existing,, Like the quote some woman on here got to fix a recept,,, 285-1000$ The homeowner is just like anyone else,, some do good some do bad. What do you call the guy that pass journyman test on tenth try? Electrician ha. I have seen some stuff by licenced guys that I wouldnt want to write home about,,, more than once. I read Bob Keis site and some of the stuff from guys there amaze me,, from guys that ought to know better,,, still havnt got a grip on this grounding thing. I can see someone like myself make somemistakes due to ignorance,,, but these guys working making a living doing this. What really bad it some handyman types, replacing water heaters and stuff,, I run across one the other day twisted wiring together,, too cheap to nut it and cut the ground wire off. I say we answer questions as well as we can, sometimes people just need some confidence.
 
  #17  
Old 07-14-02, 09:12 PM
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bungalow jeff
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When a job is explained in detail, whether a switch replacement, ceiling fan installation (what is it at, four a day?), or a shed subpanel, the wor required fora safe installation will deter those whose skill level is lacking. Knowing the level of work involved may convince a DIY'er to just hire a pro more than the "just hire a pro" advice ever will. When they don't know, they will try anyway, and blindly at that.

This forum is the best I have seen at drawing the line between step-by-step advice and suggesting a pro. I have had two of my responses declared against code by "pros", only to have one or more of the regulars post the exact section of the NEC that supported my statement each time.
 
  #18  
Old 07-15-02, 06:01 AM
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Hatteras
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What I am saying is this: Some of these people have no business doing anything more complex than replacing a switch, judging by some of the questions being asked. They are not qualified to be doing this work. Would you want your car serviced by someone who doesn't understand the basic concepts and fundementals?

sberry: I have been in the electrical business a long time. I never heard of anybody anywhere flunking a Journeyman's test 9 times. As far as I know after the third time you're out.

I never said that every electrician is qualified. Obviously some are not. And I am sure that there are homeowners that are very qualified to be doing this work. It's all about knowing your limitations and I don't necessarilly believe that some people will hire a pro because the work is too involved to do a safe job. I believe just the oposite and the homeowner will cut corners because they don't know better. Most electriciazns do know better. If they cut corners they should be reported.
 
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Old 07-15-02, 06:34 AM
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I have found no good way to judge the expertise of people asking questions here. Many people asking questions here are quite experienced, and they already know the answers to the questions they ask. They are only asking to get that warm feeling from having somebody confirm the answer that they already know.

On the other hand, we often get questions from people who appear to be quite experienced based on the detailed question. However, later posts from the same person indicate that they are really quite inexperienced.

So I try to just directly answer the question that was asked, and occasionally point out that there may be more to it than is indicated by the answer given. Some people choose to be insulted when you questions their knowledge, but I'd rather err a bit on that side than allow people to think that a complicated job is simple.

There's no perfect solution. We strive for the middle ground.
 
  #20  
Old 07-15-02, 07:17 AM
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I agree with all of you.

This is a do-it-yourself forum.

We should provide the information.

SOMETIMES (judging from the poster's responses to our answers) it is logical to conclude that they haven't got a clue, and it doesn't hurt to suggest using a licensed electrician.

We can provide the do-it-yourself information anyway.
 
  #21  
Old 07-15-02, 03:02 PM
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John, I just saw we both posted an answer to the original question posted evidently at the same time. I didn't mean to step on you. Didn't see you reply until today.

Good thoughts bad timing on my part.

Wg
 
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Old 07-16-02, 05:27 AM
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I think everyone has a vakid point to a certain degree.
The comment about some people seeming to be somewhat experienced, but later responses point otherwise may be the result of those people doing some preliminary reading/researching. They start out with remembered info from this reaseach. I am one of these sometimes. But, some people then almost consider themselves electricians. I am not one of these! I am aware that that are many complicated sitations when dealing with electricty and someone can get killed in a second with one wrong move, or down the road at some point in time due to improper wiring. I have seen the results of an electrical fire. The site and odor of a burnt body tends to stay with you a while. I just hope I have the sense to ask the dumb questions and to understand the answers which will enable me to do as safe a job as possible. If people don't know what they are doing, but insist on tackling a project anyway, they should attempt to get as much info as possible on the subject from qualified people who do know.
Some people are quite adept at doing things completely out of their normal fields and understanding instrutions, some are not safe with a claw hammer. I, myself, favor the DIY forums. People just really need to know their limitations.
There are pros and cons to both sides of the discussion.

Just my thoughts
 
  #23  
Old 07-17-02, 07:11 AM
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Just wanted to post my 2 cents on the side issue here:

This forum has been invaluable to me as a new homeowner. I took John's advice on my very first post and bought a couple of books on home wiring and read and reread them. I then lurked in this forum for many months reading everything. My first project was simply replacing switches and outlets. In fact, this forum probably saved my home since in none of the books I have does it say NOT to install 3 prong on ungrounded circuits. Anyway, I then progressed to getting permits and adding pretty complex (to me at least) circuits for basement and attic remodel projects.

I want to point out as well that other forums on this site to which I have posed relatively easy questions have been pretty rude and told me to hire someone. This forum has NEVER done that(before this thread). We all appreciate that. I have never been back to those other forums, and you'll notice that the posting traffic is much much less on those other forums than here.

I decided to try and do the work (electrical and otherwise) on my own home not because I could not afford to hire someone, but because I WANTED to do it. There is no match for the satisfaction of doing something for yourself (except maybe your first passed inspection).

So consider this a big THANK YOU to all who post answers to this forum, in particular WGOODRICH and John Nelson. Your work here is very much appreciated.
 
  #24  
Old 07-17-02, 07:59 AM
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All of the rhetoric aside, why doesn't anyone give the individual posting the question and accurate and informed answer. His question concerns voltage drop and the only way to answer his question is to perform a voltage drop calculation to determine the correct wire size. I have looked through all of the replies and I might add that quite a few of them are ponderous at best. Everyone is guessing at what size conductor to use and I have not seen the correct size given yet so I will try to do it for him.

The following the method mandated by the NEC for sizing the conductors for voltage drop. We will use a voltage of 120 volts since Crawdad said he is installing lights. I will have to use a given of 20 amps since I am assuming that's the ampacity he desires in the shed. CM= 2x12.9x200'x20A divided by 3.6volts

Cm is the wire size, 2 is the wire out and the return, 12.9 is the constant for copper wire if aluminum is used this number must be changed to 21.2, 200 is what he says the distance is, 20 amps is what he says that he desires at the load point, 3.6 is the allowable percentage of voltage drop for a branch circuit ( yes for the purpose of this calculation it will be considered a branch circuit as the feeder circuit is that which supplies the house in the first place.
If you perform the above calculation you will find that the answer in your calculator will be 28666. Ok now what? Now you have to use the NEC and turn to Table 8 of Chapter 9 for the table of conductor properties. In this table you will see that there are lots of numbers and columns, the only column that we will be looking at is the one that says circular mils at the top. Now follow that column down until you see a number that is at least as big as the 28666 that we calculated. You will see from doing this that the only number that is at least as big as this is 41740. Now follow that number in a row to the left and you will see what size wire is needed to get the full 20 amps out 200 feet while only dropping 3.6 volts. That number corresponds with a #4 copper conductor!!
This is the only way to answer the mans question. In all of the posts I have seen guessing and people saying that he should call an electrician and no that's why we are here, yet nobody did this calculation!! Using a number 10 as suggested and plugging any kind of circular saw and trying to cut with it would be futile, worst of all it would deteriorate the saw very quickly.
Point being, Quit arguing with each other give him the correct information or don't give any at all!!! All that can be done in this forum is to give the correct advice, what the individual does with that information is out of anyones control on here.
Further I would follow the advice given as to burying a conduit to run those wires. Trying to find #4 Uf wont be easyI would imagine and it will not allow for future expansion.
Hope I did not ruffle anyones feathers here but, I hate seeing the improper information given when it is as important as a voltage drop calculation and the mans time to install the wrong wire sizes only to find that he can't do what he wanted when he gets it out there.
 
  #25  
Old 07-17-02, 08:43 AM
J
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I think crawdadcreek has been given several accurate and informed answers.

Although I assume Sparksone42's analysis is technically correct, crawdadcreek is looking for "the cheapest and easiest and safest way possible." Although some of us may think this short-sighted, it is nevertheless crawdadcreek's stated objective.

Therefore I'm guessing that there is no way that crawdadcreek is going to buy and run 200 feet of 4-gauge. In my post, I advised him to use 10-gauge as a compromise between cost/simplicity and controlling voltage drop. You'll note that I said that whenever he's under 14 amps, he'll be under 5% voltage drop. Based on what he said that he plans to use in the shed, I think he'll be under 14 amps most of the time.

I hope crawdadcreek can sort though all this mountain of side discussion to come up with a plan acceptable to him.
 
  #26  
Old 07-17-02, 08:54 AM
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Even at 14 amps if you do the calculation it will come out to a #6. John I didn't mean to offend you!!! If you want to give him the advice to do it the safest and cheapest way then isn't the correct way the only means to the end? If he does install the wrong conductor size and can't use what is installed then how is it cheap? And how in the world can anyone that is in this line of work justify telling someone just what they want to hear? If you were the electrician that he called out to do the work and he said he wanted it cheap would you still install that number 10 knowing that you are liable for any and all damage it may cause? Could you sleep at night knowing the you did something that would be considered NEGLIGENT in a courtroom, something that could conceivably cause a fire? With full knowledge of what you were doing.
I have read your posts on here and from what I have seen that's not the way that you operate! You have given wonderful advice. Here I think everyone went astray just a little. If the man was not confused before posting he certainly is now.
By the way the 5% voltage drop that you mention is for the entire run from final overcurrent protective device to the point of demarcation or electric utility service. None of this has even taken into account that the 5% may have already been taken up with the service alone. These are unknown factors for us that may even make the situation worse. 3% is the acceptable voltage drop on a branch circuit!!
I am sorry if I am being anal here but, I have done far too many contracts where the homeowner attempted things like this and burned circuits and panels and breakers and tools and so forth. I am just trying to make it so this doesn't happen to Crawdad. Again, I will say that the correct information should be given if Crawdad decides that it's too expensive and he wants to do it another way, then he has to live with that, it will be his decision. You can't control what he does but, you can give him the absolute best of your knowledge.
Hopefull this is a friendly argument here I don't want to upset anyone.
 
  #27  
Old 07-17-02, 09:47 AM
J
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Your points are all valid. But it is my opinion that there is no one correct answer, and the main issue here is usability, not safety. Although 6-gauge wire will definitely provide better service, it is not required for safety.

I appreciate the lively discussion, and was not offended. But I think you had missed the fact that several post had already answered the original question. You provided a different answer, and that's fine.

I'm sure that crawdadcreek was hoping for one simple definitive answer, but I'm sure he sees now that there are tradeoffs to be considered that are not necessarily simple nor definitive.
 
  #28  
Old 07-17-02, 03:36 PM
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Wgoodrich
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sparksone42, YOu hit a few spots in your reply that could be veiwed in a different manner just for discussion purposes.

The NEC only advises a maximum voltage drop, the NEC does not dictate a maximum voltage drop. Voltage drop is only advisory in the NEC if loosely interpretted.

If specifically interpretted the Code does say that the conductor must be capable of carrying the load which could be construed as zero voltage drop while using the FPN Note where the maximum advised voltage drop is mentioned that is not enforcable as an allowance if the AHJ chooses to allow that allowance of the FPN note.

All depends on how you interpret the rules that are written for branch circuits and feeders.

When you calculate voltage drop you should calculate connected load not conductor ampacity rated load. If we looked at what was originally posted a couple of flourescent lights and a few receptacles is mentioned in the shed was discribed. These receptacles would be general use recepatcles and 220.3 dictates that load to be 180 volt amps for commercial setting of general use receptacles. From what I am understanding is expected in that shed the normal load would only be a few amps and the normal maximum load in amps would be about 10 amps to 12 amps considered as the demand load of that shed and may be used in your voltage drop calculations. If this is taken into consideration then John's 10 awg would be a realistic and economical up sizing considering voltage drop in my opinion. While I am aware that he may be rewiring this shed if he grows in the future, I took him to want what would work at this time limiting his cost but allowing it to work properly. By what he discribed I did not see any loads combined beyond the 10 or 12 amps under normal occasions.

Considering that on normal occasions this shed would not be loaded to the maximum of 20 amps. I also suggested the 10 awg as a good middle of the road branch circuit sizing.

If we were talking a commercial structure I would consider using the larger 6 awg conductors, but with the discription of occasional intermittent use the 10 awg shoud carry what he needs in my opinion agreeing with John's thoughts.

Just an opinion

Wg
 
  #29  
Old 07-17-02, 04:38 PM
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Better than TV

Boy, I never thought a simple (or what I thought was simple) question could be so complex. I posted here because I am a novice and needed an Education. Yes, I do believe that I can weight the info and decide if I can do the work myself or hire it out. This question seems to be a "hot" topic. I wanted to know my options, understanding that there is more than one way to skin a cat. One of the first replies suggests that I use 10/2, another suggests I use 10/3. At that time I was asking myself what in the hell is 10/3? OOOHHH 220v, makes sense. I don't know what I need to grow in. I don't know the min's. I will admit. I don't know much..............the basics, but I wanted to learn. YOU ALL WOULD NOT BELIEVE SOME OF THE ADVICE I HAVE GOTTEN FROM SOME OF THE LOCAL'S...........I thank each of you for your input. This is a healthy discussion for everyone! At this point however I still don't know how I am going to approach this job. I like to pidal. I run a circular saw, a sander, a shop vac, some lights so I can get away from the wife (maybe watch some TV). I don't believe (an understood gamble) I will grow into anything more. I have called and priced 10/2 burial wire and 10/3 wire and they seem to be comparable. I am steering towards the 220v hook up to give me a little extra just in case. At this point, I feel that I can complete this job, or at least I can dig a ditch!!!!!!!!!!! Boy, the stock market sucks right now!!!!!!
Thanks.........brian
 
  #30  
Old 07-17-02, 05:04 PM
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Wgoodrich
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Crawdadcreek, I apologize in my last reply. While I was trying to show an alternative method of looking at the subject for sparkone42 to consider I was not thinking of you. The 10 awg I was referring to in my last reply still was referring to 10/3 with a multiwire circuit. If you think in the line of the voltage drop calculations you would have one 240 volt feeder that would produce two branch circuits 120 volt rated with a shared neutral. When you install 240 volts instead of 120 volts you are either cutting the load in half carried by two hot lines instead of one hot line. If you have a 240 volt circuit compared to a 120 volt circuit going the same distance you would be approximately cutting your voltage drop in half in your calculation. This is why I advised 240 volt instead of 120 volts to help address voltage drop. Teh 200 feet distance is more easily carried by 240 volts cutting the voltage drop to a livable level.

Sorry I did not make myself clear in what I was thinking.

Wg
 
  #31  
Old 07-17-02, 05:32 PM
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10/3 is useful even if you never use any power at 240 volts. It will simply give you twice as much power as 10/2 at 120 volts, and will incur less voltage drop to boot. Although I suggested 10/2, 10/3 is a good alternative. However, even if you use 10/3, I still recommend against a subpanel. Just use the 10/3 as a multiwire circuit. I know that you may not yet know what a multiwire circuit is, but you will as you get closer to doing the job.
 
  #32  
Old 07-17-02, 07:09 PM
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Wgoodrich, no apology needed here. This is an education for me and being a new home owner there are alot of things I have never thought of doing on my own before.

A general comment.
Admitting one is ignorant (notice I did not say STUPID) is NOT foolish. In my opinion, there are no stupid questions............I set a perfect example don't I........

10/3 makes sense because of the distance. One line can run my lights (3- 40w flourescent lights and a 30w flourescent fixture over my '4x8' work bench) and the other can supply my limited tool usage. This will add to the cost ( a 30a, 220 v breaker + 50' of wire as opposed to connecting to the already present 20a lead) but the cost will be well worth it I think. Please tell me If I am wrong, but this is the plan.
1. Install a 220v, 30a breaker in the 200a breaker box in the house.
2. Connect 10/3 wire with a ground from this breaker and run it through conduit (buried at least 12") 250' to the shed.
3. Connnect this to a 220v fuse box with 2- 30a fuses in the shed. (John N... is this what you mean by a sub-panel?)
4. Connect lights/switches etc. using 12/2 wire
Hope you guys are'nt getting tiried yet....................
Thanks......brian
 
  #33  
Old 07-17-02, 07:27 PM
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You may use a 30-amp 240-volt breaker in the main panel if you wish (although I'd still recommend 20-amps to avoid unreasonable voltage drops), but you may use no higher than 20-amp breakers in the shed.

One of the reasons that I recommend against a subpanel in the shed is that you will be required to install two grounding rods and the grounding conductor to connect them to the panel. This is an additional complexity and expense that you don't need and provides virtually no benefit.

Instead, when that 10/3 reaches the shed, merely feed it into a junction box from which emerge two 12/2 cables. One 12/2 connects to black, white, and bare. The other 12/2 connects to red, white and bare. Install a master cut-off switch as the first box on each 12/2. Install a GFCI receptacle as the second box on each 12/2. If you follow the advice in this last paragraph, then you must use a 20-amp 240-volt breaker in the main panel rather than a 30-amp 240-volt breaker.

When I was talking about 12 inches burial depth, I was talking about GFCI protected UF cable. But now that you're talking about conduit, you only need to bury it 6 inches deep if you use either right metal conduit or intermediate metal conduit. However, if you use nonmetalic conduit, you'll need to go 18 inches deep.
 
  #34  
Old 07-17-02, 09:30 PM
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Originally posted by John Nelson
You may use a 30-amp 240-volt breaker in the main panel if you wish (although I'd still recommend 20-amps to avoid unreasonable voltage drops), but you may use no higher than 20-amp breakers in the shed.

One of the reasons that I recommend against a subpanel in the shed is that you will be required to install two grounding rods and the grounding conductor to connect them to the panel. This is an additional complexity and expense that you don't need and provides virtually no benefit.

Instead, when that 10/3 reaches the shed, merely feed it into a junction box from which emerge two 12/2 cables. One 12/2 connects to black, white, and bare. The other 12/2 connects to red, white and bare. Install a master cut-off switch as the first box on each 12/2. Install a GFCI receptacle as the second box on each 12/2. If you follow the advice in this last paragraph, then you must use a 20-amp 240-volt breaker in the main panel rather than a 30-amp 240-volt breaker.
Let me suggest that you can use a double pole "snap" switch to open both legs of the multi wire branch circuit simultaneously. You are not required to have a GFI in a circuit that does not have receptacle outlets.

When I was talking about 12 inches burial depth, I was talking about GFCI protected UF cable. But now that you're talking about conduit, you only need to bury it 6 inches deep if you use either right metal conduit or intermediate metal conduit. However, if you use nonmetalic conduit, you'll need to go 18 inches deep.
The use of rigid (RMC) or intermediate (IMC) metal conduit will save effort on digging but you may spend more effort on fitting the RMC. Given the length of the run you might want to consider hiring the trenching out to a heavy equipment operator.
--
Tom
 
  #35  
Old 07-18-02, 08:34 AM
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There seem to be some misconceptions here.

1. Just because you carry 240 volts to the shed will not cut the voltage drop on a 110 volt circuit. It's still a 110 volt circuit!! Now there will be two of them that's all. The original calculation still stands.
2. I used 20 amps in the calculation as it appeared that's what Crawdadcreek was looking to have available in the shed. Had he given me specific loads I would have used those specific loads in the calculation. I used the formula that determines wire size for a given load at a given distance.
3. Wg you are correct that it is not a requirement of the code that you consider voltage drop. However, don't you think that Crawdadcreek would like to be able to run the saw and the vacuum that he mentioned. At one point I was told by John that he was looking for about 14 amps in the shed and I went back and used that figure in the calculation and it still comes out to a number 6 wire. If you have a saw that draw 8 amps of running current and you use it to cut wood and it begins to bind any, you will exceed that 14 amps, now wouldn't that be a bummer!!!
As for the reference to the code I merely used that to show that I am not pulling this out of my hat. Why would they go to the trouble of providing specific rules and formulas for voltage drop if they didn't think it was important? Again, I will say that the cheapest way to do something in my experience has always been the correct way.
4. hornetd suggests running the number 10 to a junction box and then connecting it to two 12/2's. If you use a 30 amp breaker at the main panel in the house, where is the protection for the 12/2's that will be connected to each of the circuits from the 10/3?

Crawdadcreek for your sake, if you follow the info about using a #10 wire at that distance(I think I even saw that you said 250' in a later post) put it in conduit! At least that way if I am right and you have trouble using your saw and so forth you will be able to change the wire out.

Here's a question for everyone and I will be curious as to what answers it will garner... If you install a water pump that draws 15 amps of current which way will it be cheaper to operate, 120 volts or 240 volts?

Again I will say that I am not trying to cause problems here but I strongly feel that you are all giving this person some bad info. That's just my opinion though, take it for what it's worth.
 
  #36  
Old 07-18-02, 09:39 AM
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The 240v will help on the voltage drop overall if the loads are balanced evenly between the 240v.


As to your question about the water pump drawing 15a is it drawing 15a @ 240v or 15a @ 120v.

If the current in your equasion is constant then the 120v motor will be cheaper to run. 120v x 15a = 1800VA
But if 240v x 15a = 3600VA

Still then youd have about a 1hp motor with 120v but about a 2hp motor with the 240v.

But if you actually meant if you had a motor able to run on either 240 or 120v then its a tossup.
You would run about half the current on 240v as you would on 120v so that could equate to smaller conductors and that might mean a smaller raceway. The downside would be you would have to use 2 spaces in a breaker panel instead of one. But at a distance you could use the 240v and help out with voltage drop problems.
 
  #37  
Old 07-18-02, 09:56 AM
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There is no tossup!! Yes, I meant the motor was capable of running on both voltages.
However, the answer to the question is the motor will cost the same to run either way. Power is purchased based on killowatt hours of use. If you have a one horsepower motor it will take 746watts to run that motor no matter how you hook it up. Therefore it will cost the same to run at either voltage.
This is one of the most common incorrectly answered questions there is. 746 watts is 746 watts no matter what voltage you use!
 
  #38  
Old 07-18-02, 10:31 AM
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Notice I gave the pros and cons of using 240v and 120v, the cost is still the same. It is a tossup on whether the advantages outweigh the disadvantages I listed below. I never contested the issue that the cost would be the same, I agree there.
 
  #39  
Old 07-18-02, 11:32 AM
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DaveB correctly identified the reason why I said that the voltage drop would be less with a multiwire circuit. In fact, when the load is balanced between the two 10/3 hots, there will be only one fourth the voltage drop that would be seen if all the same loads were on a regular 10/2 circuit. That's because the outbound voltage drop is cut in half because the current on each ungrounded wire is half, plus the fact that the return trip voltage drop disappears entirely.

I think almost everybody here would have correctly answered the motor question. But I don't know what that has to do with this discussion.

And the reason that Sparksone42 and I came up different wire gauges for the same application has to do with how we defined an acceptable voltage drop, not how we did the calculation. We simply disagree on that. But we do all agree that if crawdadcreek's needs increase, he'll need bigger wire. That's a risk that only crawdadcreek can decide whether or not to accept. However, he did throw in a TV in a recent post that he hadn't mentioned before. Sounds like his needs are already increasing and he hasn't even started.
 
  #40  
Old 07-18-02, 04:42 PM
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sparksone42 has a point if you look at in a way that if we ran 240 volts to that shed the heavy load would be the 120 volt saw that will only use one of those two hot wires.

However on construction sites the Utility company often force a temporary to be placed 200' or more from a house being built. Normally those builders then will install a 10/2wGrnd UF cable to the structure and protect it with the same 20 amp breaker as normal. The 10/2 wGrnd is used to reduce voltage drop. Worm drive power saws are then commonly ran off 100' extension cords plugged into that 10/2wgrnd reduced to 12/2wGrnd pigtails within the box to normal duplex recpeptacles. They seem to be doing fine building a complete home off that 10/2wGrnd with more distances than we are talking here and crawdedcreek most likely will not be building a house with a worm drive saw off the receptacle in his shed.

The paragraph above was mentioned to show the reason that John and I both felt that if a 10/3wGrnd 240 volt branch circuit protected by a 20 amp breaker in the house panel and reducing to 12/2wGrnd while inside the shed with a double pole switch used as a main disconnect form and no ground rod installed would fullfill crawdadcreeks desires.

I suspect that John and I both feel that if crawdad creek is planning on increasing the load in the shed then he may want to install a larger service in the shed but that is only able to be decided by him as to whether his loads are going to grow in that shed in the future.

By what he discribed the 10/3wGrnd will serve him well using a less that optumum voltage drop condition but weighing cost factor and expected use as major factors in his design of power to his shed.

Just an opinion

Wg
 
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