Suggestions for Electrical How-to Books

[davidshackelford]

I am wanting to learn more about electrical wiring (specifically for my shed). Does anybody have any suggestions for good books/articles on small wiring projects?

Some questions I am trying to find answers to:
My shed is over 125 ft. from my breaker box, so I will need to find out if I am going to experience substantial voltage drop. (Will I need to put a subpanel in the shed?) (What type of wire to use in an underground trench? Is conduit needed) I am wanting to put in a ceiling fan, flourescent lights, 10 outlets, and the switches for the fan and lights. How do I go about doing this?

Am I asking to much for a book...should I just find an electrician?

Thanks for all the help this forum has given me!!!

[Tom R]

David,

Beings mistakes in electrical work can be 'life or death' situations, I would definitely recommend an electrician. The way to save yourself some of the expense is to pre-dig the trench for him. Local codes vary on the depth, probably at least 12" or 18" if you're driving over it.

You're right to be concerned about the voltage drop, you probably need to use stranded #8 or #10 wire in plastic(?) tubing, and yes, I would think you would want/need a sub-panel. It would need it's own grounding rod and the neutral and grounding bars would need to be separated.

This job is a little more complicated than just your basic 'running some new electric'.

The above info is much more opinion than advice, I'm a carpenter. Hopefully, someone more qualified will chime in.

[davidshackelford]

Thanks for the advice!

If there are any electricians reading this, and you were to come in on this job with the trench pre-dug, what would be a ballpark estimate?

I am looking at:
-10 outlets
-1 Ceiling Fan (I provide)
-Flourescent Lighting (For 8' x 14' shed) (I provide)
-(+/-) 150 ft. from breaker box

I have typical woodworking tools:
-3 hp Table Saw
-14 amp circular saw
-Reciprocating saw
-18v Drill (charging station)
-Jig saw (in near future)
-Router (in near future)
-Miter saw (in near future)
-5 hp Shop-Vac
-And several small fans (its HOT)

I do not plan on purchasing any tools that would need anything other than a standard socket (no 240v).

Thanks!
-David

[steeve]

there's nothing wrong about learning electricity, any book store or home depot has it.dont have to play with live wires,and "you shouldn't" but a least you will understand the way it works. wireing up a shed is not more difficult then adding one single outlet.when you know what your doing you wont burn.... :twisted:

[Vector]

A very good book for understanding residential wiring in general is "Wiring a House" by Rex Cauldwell

http://www.amazon.com/exec/obidos/tg/detail/-/1561585270/qid=1099758534/sr=8-1/ref=pd_csp_1/002-1695749-8696019?v=glance&s=books&n=507846


Some specific comments I have about your shed.

Since you are talking about a significant amount of power, I would definately run a sub-panel. It will allow for expansion in the future too (and despite what you may think now, you probably will want more power someday).

I would run a 60A sub-panel. For this you will need:

a double-pole 60A breaker for your existing panel
#6 wire will work, but the voltage drop will be about 3.2%, #4 will limit the drop to 1.9% (anything under 5% is "acceptable," but I'd still go to #4)
4 conductors, two hots, one neutral and a ground.
You can run 4-3 UF-B wire for this in a trench 30" deep
- or three #4 THWN and one #8 (or larger) THWN for the ground, in plastic conduit (Sch 80), 18" deep.
- or the same THWN wires in rigid metallic conduit, as little as 6" deep.

In the shed, a 60A breaker panel (or higher, often 100A is cheaper than 60A, and can be used, as long as the breaker in the main panel is 60A).

In the sub-panel you will need to keep the ground bus and neutral bus separate. Usually this is done by removing (or not installing) a green bonding screw, and adding a seperate ground bus bar (usually under $10). In this subpanel, you never connect neutral wires to the ground bus and vice-versa (unlike in your main panel where they can be mixed). You will also need to drive an 8' ground rod into the ground outside of the shed and connect it to the ground bar. Use #4 bare copper, as anything smaller requires conduit from the panel to where it enters the ground.

I would wire at a minimum 4 circuits:

1x15A for Lighting. You don't want the lights to shut off because you had a tool bind up and trip a breaker. Keep it seperate.

2x20A for your tools. You may always be working alone, but I've found that the one time you're working with someone else there's nothing worse than tripping the breaker every time you both run a tool at the same time.

1x15A for your fans, charger, and any other misc stuff.

That said, get at least a 6 space panel, usually going larger doesn't cost much more, so I'd probably get a 12. You might just get a nice table saw or lathe or other tool that works on 240V, and it's cheap to provide for that expansion later.

All recepticales in your shed will have to be GFCI protected. You can either put GFCI breakers in on the circuits that will have outlets (expensive, ~$50/circuit) or install GFCI outlets as the first outlet on each circuit (~$15/circuit).

The circuits inside the shed can be wired with 12-2 NM-B for the 20A circuits and 14-2 NM-B for the 15A circuits. Unless the wires are going to be exposed to damage (on the surface of the walls, for instance), then you would want to run #12 THHN (or #14 for 15A) in conduit.

I know all of this seems like a lot, but it's not really that bad. Read the book first regardless, it does a very good job of explaining things.

Also, a copy of the code is invaluable, but unless you're really experienced with it, it's very confusing to read. An "illustrated guide" to the code is good to have along with the code itself.

Disclaimer: I am not a licensed electrician, but I am very comfortable doing electrical work, and I know how to read the code books ;)

[Vector]

One last thing.

Don't even think about doing this by yourself without pulling a permit. The cost of the permit is worth every penny in knowing that you did it right.

If you hire an electrician, by all means dig the trench yourself, it will save you significant money. Make sure he pulls a permit and has the work inspected though. An electrician who doesn't pull a permit is hiding something (like not being licensed, for instance).

[steeve]

right on...who needs books when you have Vector... 8)

[Vector]

Well, *I* need books. And I do suggest you read the books too :)

[steeve]

Vector,

no offense, *I* do have and read too...but by reading your posts i ll have more time doing the job... :D

[bkrahmer]

I disagree with the grounding advice. The book that I have (Taunton's, methinks) says that you are NOT to ground subpanels. There should be only one ground path for the whole house, subpanels included. Separating the ground and neutral bars is correct. I have electric in my shed. I used 10/3 UF, run of 60 ft, max load about 12 amps. I ran the ground back to the panel.

I don't buy all of the heavy warnings. Of course electricity is dangerous, but if you're not stupid, you'll be fine. Get the permit, and have it inspected, though.

As far as voltage drop, first you'll want to find your voltage drop from your transformer to your main panel, then calculate your reasonable max load, and put it into a voltage drop calculator. I've read that 2% drop is acceptable. That made my 240 ft run to my main panel with 4/4/2 acceptable. Google 'voltage drop calculator'. There's a couple good ones...

cheers

[Tom R]

But he's not talking about a sub-panel 'in' the house, - - he's talking about a sub-panel in a 'remote' location (shed), - - and it definitely DOES need a grounding rod.

[steeve]

wow... how would you explain elect.panels using metal shielded wires or running through metal pipes, if one box is grounded the're all grounded ...
one ground path, means one ground to earth...
and about neutrals the're already grounded in the panel... in case of a short the ground takes the current back to panel out to pole(transfo),down the ground(earth) shock security....
if you want to do a little experience, take a light tester cross the neutral and ground and see the result...:twisted:

[Vector]

There should be one place, and one place only where the ground and neutral are bonded together, and that should be right at the service entrance point.

I think that's what you are talking about when you say "one ground path"

In reality, the more paths from that point to actual ground the better. That's why you not only bond the ground to the service neutral there, but you also are required to (in new installations), install two ground rods (or one if you can prove <25 Ohms resistance), plus ground to the incoming water service.

And if you extend power to an outbuilding, even if you provide a ground wire back to the main panel, you are required to drive a grounding rod there also.

Metallic conduit will act as a ground. In some cases, it can be the only ground. But steel with multiple mechanical connections is nowhere near as effective a conductor as a single pice of copper. If it's buried, though, the conduit will work as one great big grounding rod, and probably be the best ground (short of having a nice metal well casing) you could ever ask for.

Grounding is probably the single most misunderstood part of residential wiring.

[steeve]

like i said, who needs books when you have Vector :lol: good job...

[bkrahmer]

Vector, I think you are right. I believe I confused an interior subpanel with a subpanel in a different building. My bad. :P Although, I know that it does work! ha

[Dragon]

Vector, I think you are right. I believe I confused an interior subpanel with a subpanel in a different building. My bad. :P Although, I know that it does work! ha

I saw a truck once that had single wire running lights attached to a wooden bed and they worked. The only thing we could figure is that the wood (fresh sawn oak) had enough moisture content in it to provide a ground path to the frame.


It still doesn't make it right.

[bkrahmer]

> It still doesn't make it right.

No kidding, dude. That's why I admitted my mistake... Lighten up, will ya?

[Dragon]

http://www.mideastclick.com/forums/images/smilies/thk.gif

[preston]

Looks like this is an older thread but here is my 2 cents on a good book...

I thought that the Black and Decker's "Complete Guide to Home Wiring" was a fantastic book. Had a lot of good information, pictures, and wiring diagrams in it...

http://www.amazon.com/exec/obidos/tg/detail/-/0865734291/103-2753845-9478257?v=glance

Preston

[Sparks]

As far as understanding electricity and especially grounding and bonding, which as Vector stated is by far, the most misunderstood concept of electricity, read,read, read, until you get it. Then buy yourself a multimeter and play with it, you'll learn a ton just by doing that. Vector, you're obviously very well read, I just have to ask why you would say that #6 wire is ok for 60 amps? Around here it's 50 amps max, the 90c rating is only useful for derating purposes. I could be missing something so please explain your response.

[Vector]

Vector, you're obviously very well read, I just have to ask why you would say that #6 wire is ok for 60 amps? Around here it's 50 amps max, the 90c rating is only useful for derating purposes. I could be missing something so please explain your response.

You know what? That's a very good question, and I'm not sure of the answer.

NEC 2002 rates 6ga. for 55A at 60C. I *believe* there is some article athat allows you to protect that wire with a 60A circuit breaker, as long as the actual load (or estimated actual load) is under 55A. But I'll be honest, I don't know the reference. I know that it is not unusual to use 6ga for a 60A feeder.

I also know that if something is right on the fence like that, I'll personally always go for the larger wire. I know that while I mentioned #6, I stated that #4 was the way to go.

Heck, I ran 3/0 copper the two feet from my main panel to the meter for 200A service when 2/0 would have been fine.

And finally, free advice is often worth every cent you pay for it :P

[Sparks]

LOL about the free advice part. I personally wouldn't worry at all over running 6 to that shed. I was just concerned about the inspectors opinion and the NEC. I believe the NEC "recommends" a 3% max voltage drop which #6 would be stretching that a bit. I was also just assuming the job would be done in UF, being it's just a shed, and UF has a 60c rating at I believe 55 amps. Good advice on the grounding, there are still a lot of Journeymen electricians out there who still think driving a ground rod at a light pole running on 277 or 480 with no ecg back to home makes it safe. It's amazing there aren't more electrical related deaths with some of this mentality.

[Rich]

NEC says 5% voltage drop maximum. The only reason I know that (the small bit of electrical I do know) is we just went through that very thing. 1000 amp service to the main house at 280' with 500cu runs had (in our situation) about 4.3% to the longest runs in the house.

[Sparks]

OK, I don't want to beat a dead horse and I don't want to get caught up in all the minor technicalities, but, this is a technical forum by design so here go'es. The 2002 NEC states: Conductors for feeders (that's what we're talking about) as defined in Article 100, sized to prevent voltage drop exceeding 3 percent at the farthest outlet of power, heating and lighting loads, or combination of such loads, and where the maximum total voltage drop on both feeders and branch circuits to the FARTHEST outlet does not exceed 5 percent, will provide reasonable efficiency of operation. End. So technically, 3% is the max for feeders, 5% max for all the circuits to the farthest outlet the way I understand it. Again, that's from 2002 NEC but I don't think 2005 says anything different but I haven't read it yet so I could be surprised.

[Rich]

Ok - a little more technical than the way I stated it :) That's the way our engineer was figuring it - 5% to the furthest receptacle.

[Sparks]

Whew, glad we got that cleared up so I can sleep tonight. :lol: Hope everyone has a happy holiday.