Electrical wiring

[Jim Behning]

I am notorious for flipping letters around. Isn't dyslexia just a wonderful thing?

Anyway it was not my argument.

[Mike Marlow]

Oh hell - we all do that from time to time. It's what makes us loveable...

[Mike Marlow]

One who lacks knowledge on a topic is far better served by telling the electrician what functionality he wants and leaving the how-to's to the person most knowledgeable - the electrician. BTW, no - all electricians are not going to wire with 12/2 on 220 and 10/2 on 110. Just the opposite. And yes - for the most part, all electricians are going to wire the same way - based on the requirements of the circuit.

[Tom Veatch]

I won't argue against the point of specifying the desired functionality to the electrician - that's just good sense. But I do take a mild exception to the "better served" part. It's been said that a "little knowledge is dangerous", but I firmly believe that ignorance is even more dangerous.

Before anybody gets incensed, "ignorance" is the opposite of "knowledge", not the opposite of "intelligence" and is not an insult. None of us know all there is to know, so we are all ignorant of more things than we have knowledge of.

I applaud the OP's question. Any attempt by a person to convert a little ignorance into a little knowledge is a laudable pursuit.

Tom Veatch Wichita, KS USA

[Mike Marlow]

Oh, I applaud anyone's interest in gaining new knowledge. That however, is not the point of Robert's and other comments about seeking qualified help on some things when one's level of knowledge is so low. And my follow on comment in response to you was simply that one would be foolish to expect that a couple of posts in a woodworking usenet newsgroup is make one capable of directing an electrician in how to perform a task. That would be a dangerous amount of knowledge.

[Puckdropper]

Tom Veatch wrote in news: [e-mail]:

*snip*

*snip*

I know something about everything. Sometimes I know that I don't know. ;-)

Puckdropper

[Hoosierpopi]

In contemporary wiring, individual wires run in a sheathed cable. "Two- wire with ground" and "three-wire with ground" cables are available. Two-wire with ground cables have a black wire, a white wire and an uninsulated ground. Three-wire with ground cables have a black wire, a white wire, a red wire and an uninsulated ground. Older houses may have "knob and tube" wiring-a two-wire system. With this system, individual wires are insulated with white or black treated fabric.

from Google Search using "Home Electrical Wiring Basics."

[Hoosierpopi]

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"10/2 and 12/2 only have 2 wires."

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Gosh, bet that makes the Code Enforcement people very angry. This is why you need to do your own, independent research. Lots of folks have opinion they are willing to offer as answers on the "net." Of course, all you had to do was drop by the hardware store, or Lowes, or HD, etc where you could get a touchy feely answer and see for yourself.

[Hoosierpopi]

Repairs and Basic Wiring Projects: Planning a Circuit

By Terry Peterman, the Internet Electrician Summary: Planning a circuit in your home requires examining some basic rules regarding the number of lights permitted on a circuit, and recommendations for mounting boxes, receptacles and switches.

When planning to hook up a circuit, whether it is a new one directly from the breaker panel or adding to an existing one, here are some general rules to follow :

Maximum Lights Per Circuit

You are only allowed to put a maximum of 12 lights on one 15 amp circuit, but try for between 8 and 10, if you are combining receptacles and lights.

Remember that switches don't count as outlets. Run a separate circuit for any large appliances, pumps, and motors etc.

Mounting Boxes

Start by marking the studs where you want your receptacles, switches, and lights to be located. Then mount your outlet boxes.

Screws are required for octagon boxes but you can use either screws or nails for switch and receptacle boxes. The important thing to remember is to make the boxes secure because, once the drywall is on, it's hard to re-attach them if they do work loose.

Don't forget that you must leave the boxes sticking out from the face of the stud, slightly less than the thickness of the product that the wall will be finished with.

Mounting Receptacles

Mount receptacles about 300 mm (12 inches) above the floor. The general rule is that a receptacle is required for every 3.6 meters (12 feet) of usable wall space.

You are probably curious as to what useable wall space means exactly...any measurement from the corner of a wall to a closet, fireplace, or to where the door swings open is considered useable wall space but, only if the wall is over 900 mm (3 feet) to begin with.

A receptacle is needed every 3.6 meters (12 feet) along a continuous wall space so that at no time can a cord connected devise be any more than 1.8 meters (6 feet) from an outlet. Also remember that there is no maximum number of outlets, so make sure you have enough, and that they are placed in convenient locations once the room is finished.

Mounting Switches

Mount switches on the inside of rooms opposite to the side that the door opens. Make them as close as practical to the door opening, but not so that the cover plate will interfere with the door casing.

The height is fairly flexible, but should be consistent and practical (any where from 1.1 to 1.3 meters or 44 to 52 inches).

[Tom Veatch]

Then I would say you've advanced to the 2nd level of knowledge on that particular topic.

1. Don't know that you don't know.
2. Know that you don't know.
3. Know that you know.
4. Don't know that you know.

Tom Veatch Wichita, KS USA

[Morris Dovey]

| Then I would say you've advanced to the 2nd level of knowledge on | that particular topic. | | 1. Don't know that you don't know. | 2. Know that you don't know. | 3. Know that you know. | 4. Don't know that you know.

This sounds remarkably like a former Secretary of Defense's semi-coherent ramblings on Middle East intelligence...

-- Morris Dovey DeSoto Solar DeSoto, Iowa USA

[Doug Miller]

Thanks for the endorsement, Rod. I'll try to clarify a few things that seem to need it, and correct a few things that definitely need it. Would've jumped in earlier, but I was out of town for the weekend.

"You are only allowed to put a maximum of 12 lights on one 15 amp circuit" -- nonsense. There is no such limitation in the Code for residential installations. The frequently-claimed limitation on the number of outlets on a circuit doesn't exist either, for residential installations.

+++++

The discussion so far of the number of conductors in a nn/2 or nn/3 cable has been only partially correct. Nobody has yet given the complete answer, which is:

1) In cable intended and approved for use in premises wiring -- NM ("Romex"), BX, AC, UF, etc. -- the number following the slash *does*not* include equipment grounding conductors which *may*or*may*not* be present. Thus 12/3 Romex cable contains three insulated 12-gauge conductors (black, red, and white) and usually contains a fourth conductor, either bare or with green insulation.

2) In cable intended and approved for use in cord-and-plug connections, the number following the slash indicates the number of conductors in the cable - period - without regard to their use. Thus 12/3 Type SJ cable contains three insulated 12-gauge conductors, usually black, white, and green, and that's all.

3) The above two categories are mutually exclusive.

+++++

"When a c'bkr is in a panel, it is derated by 20% to handle the panel heat generated by adjacent c'bkrs.." -- nonsense. Circuit breakers are *required* by Code to be placed in a panel or other similar fixture [Article 240.30] and no derating is applied for doing so.

+++++

"#14 can only handle 15*80%=12A on a continuous basis." Correct, but incomplete and potentially misleading, as it omits the Code definition of a continuous load: "where the maximum current is expected to continue for 3 hours or more." [Article 100] This is *not* a usual, typical, normal condition.

+++++

"Either 12/2 or 12/3 will contain a green ground conductor." -- nonsense. In NM cable (the type used most frequently in residential construction) the grounding conductor is uninsulated.

+++++

"12/2 would be used for a 240V/1Ph/60Hz service." Correct, as long as it's a

15A or 20A circuit. Higher-current circuits require larger wire.

+++++

Some erroneous statements were made about how 240V circuits need to be wired, but they've already been adequately corrected by others, and I won't bother to rehash that.

I can attest to that as well.

This is one of those topics that's always sure to generate a lot of traffic, including a large number of confidently delivered but incorrect answers. :-)

[Tom Veatch]

No, it's more like the redneck statement of the three laws of thermodynamics;

1. You can't win.
2. You can't break even.
3. You can't get out of the game.

Tom Veatch Wichita, KS USA

[Bradford Chaucer]

10 or 12 is the wire size, 2 or 3 the number of conductors. All Romex type cable has a ground which is not referenced as an "official: conductor. 10/3 cable has 3 10awg power carrying conductors and a ground. The 3 conductors are white (neutral) Black and Red (hots) and is used in balanced 240/120 volt circuits (120 from each hot to neutral, 240 across the hots) 10/2 has a white and black and is used in 120volt circuits only.

You have 2 issues in wiring a shop, the size of the conductors and the type of circuits.

Size your conductors based on length of run and branch current rating. 12 awg is standard for 20amp, but I would use 10 for longer runs.

When I designed my shop I ran both general purpose 120volt, 20 namp circuits and 240volt 20 amp circuits around the shop. the 120s are for the light stuff, the 240s for larger tools like my lathe, DC etc.

I also ran several dedicated 240volt 50amp or larger circuits for stuff like welders, compressors etc (Yes, I'm a turncoat, I also work metal!!)

Fri, 10 Aug 2007 14:19:22 -0700, [e-mail] wrote:

[LRod]

Are you saying that I was in error using 10/2 for my 240V water heater?

I don't think so. There is no requirement to use xx/3 wire for 240V if a neutral isn't called for (as it is with ranges and dryers since the '90s). Your table saw or planer circuit could just as correctly be run with xx/2 cable.

The NEC makes a provision for using the white conductor in NMC (Romex) as a hot lead for just that circumstance (and also for switching):: you must mark the white wire at each end as a "hot" conductor. A piece of tape will do, although I used a red magic marker coloring each white conductor in all my 240V shop circuits--I could just as easily have colored them black, as there's no "polarity" marking requirement, either.

[Doug Miller]

All correct up to this point, but now you go astray:

Completely incorrect. Since a 240V circuit has no neutral conductor, only two hots and a ground, 10/2 with ground is perfectly fine for use in 240V circuits up to 30A. Three-conductor cable (such as 10/3) is needed for a 240V circuit only if there are also 120V loads on the circuit; an example of this would be an electric dryer, which has 240V heating elements and (typically) a

120V motor. The 240V motors which are typically found in woodworking tools have no neutral, only two hots, and will get along just fine on circuits wired with two-conductor cable.

[no spam]

I wired my entire place but almost made the same mistake. I almost bought

10/3 because I wanted to have a ground wire.

Yes buy all means let's make sure the government gets its pound of flesh. I paid all the money and got all the permits and did all the work myself. My final inspection consisted of a guy showing up and sitting in his truck while we talked about the old PBY flying boat. After about 10 minutes he signed my paperwork and drove off to do his next inspection.

A permit ain't going to help that. For onething people like that are the very ones who don't get permits.

[no spam]

I know copper wire has many advantages over AL wire but I have a question or two.

First off why is almost all the 'big' wire AL? When I started service here I was required to buy AL wire to connect the meter to the breaker box on the pole and to connect that box to the breaker box in the trailer.

Also can you even buy 'small' AL wire, e.g. 10 ga? If so is it that much cheaper than Cu?

Would anyone here use AL wire for anything?

[no spam]

A couple of more points. 1) The more you now about things the easier it is to calculate your building cost.

2) If you have people bid on a project it helps to know just what they are planning on using. If Joe's Power bid is lower than Bill's Power its nice to know that one reason is Joe's is planning on using smaller wire.

Personally, when it comes to wiring bigger IS better. Even more so when it comes to a workshop. I'm looking at building a new home in a few years and if I can afford it I will 'over wire' the entire house for a couple of reasons. First, look around your house now and think about how it looked 10 years ago. How many more electrical items do you have now? How many more might we have in 10 more years?

Second, its much more difficult to have an electrical fire if you wire a 20 amp breaker with wire that will carry 40 amps or so.

Third, if you need to 'upsize' later its a lot easier to just put in a larger breaker than putting in new or more wire.

[dpb]

Cost -- compare the price for large diameter Cu vis a vis Al and you'll see they "why"...

It would be unusual to require Al, most will accept either as most terminations these days are Cu/Al compatible. If the service gear was rated for Al only, then it would make sense.

Another reason for Al is that it bends more easily so for larger sizes it is easier to handle.

Al for service entrance, feeders, etc., sure...

I would expect a very high fraction or more of those "here" have Al in their own residences in at least those applications.

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