Electrical wiring

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In recent posts I have heard mention of 12/2 and 10/2 wire, as well as 12/3 and 10/3 wire. What is the difference and what would you wire a new shop with?
I assume the 12/2 and 10/2 mean with ground.? What is the extra wire in the 12/3 and 10/3 for? Is that for wiring 220V?
Jim
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10/3 and 12/3 are with ground. Also there are only 3 wires in those cables.
10/2 and 12/2 only have 2 wires.
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Leon wrote:

That's incorrect. The second number is the number of conductors. Ground isn't counted as a "conductor".
Chris
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You can (or could anyway) by 10/2 with no ground. 220 wiring needs two hot conductors, a center conductor (which may or may not be at ground), and a ground wire. Jim
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...

You only need the "center" (neutral) conductor if you are going to be taking 110 off the circuit as well as 220. In that case, you need a 4 wire (3 + ground) cable. If the circuit is dedicated to 220v service only, then the neutral is unnecessary and three wire ( 2 + ground) cable is sufficient.
Haven't read all the other posts, so don't know if anyone replied to the OP relative to the gauge. But, if not, then the "10", "12", "14", etc in the designation is the wire gauge or size. Typical use is 14 gauge for circuits not to exceed 15 amps, 12 gauge for 20 amp circuits, 10 gauge for 30 amp, etc. Circuit amperage is limited by the size of the breaker the wire is connected to.
I'm not an electrician and only have nodding acquaintance with NEC requirements. However, I'd recommend that if you (the OP) is wiring a shop, use 14 gauge only for dedicated lighting circuits and 12 gauge for all the 110v branch circuits. Its a little more expensive but its a one time expense and with the proper receptacles, you've got 20 amps available at the wall sockets.
Tom Veatch Wichita, KS USA
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No. 220 works just fine with two conductors and ground. You only need neutral if you will be taking 120v loads off of one of the legs.
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-Mike-
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All of the wires in my 10/3 are insulated.
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It's unusual to find ground insulated in a romex type wire. Are you quite certain of this Leon?
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Quite sure however this is not Romex, it is a some what flexible extension cord that I have made up. I did not picture Romex when answering the question. Doh!
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No, no. X/2 means X conductors *plus* a ground. Two colored insulated conductors, plus a bare ground conductor. Typically today, it's difficult to find wire without a ground wrapped in it. In the old days it was easy to find that and the terminology made accurate sense, but these days ground is always there. So, the actual wire count in X/2 is three.
X/3 also indicates the number of conductors not counting ground, so there are three colored conductors, *plus* ground. Useful for such things as three way switches, etc. Likewise, the actual conductor count in X/3 is four.
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YES! My head was not in the right place, he did say wiring the shop. I was thinking an extension cord, not Romex. My extension cord is a 10/3 with 3 insulated wires.
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Oh hell - we all do that from time to time. It's what makes us loveable...
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Do-It-Yourself 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).
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xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
"10/2 and 12/2 only have 2 wires."
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
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.

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snipped-for-privacy@gmail.com wrote:

The first number is the wire guage, the second is the number of conductors in the outer sheathing (not including ground).
As for what you would use, before wiring the shop you should have a good picture of what types of equipment you'll have and where it will be. You then simply wire accordingly. My shop has a mixture of #14, #12, and #10 wiring, depending on purpose.

The extra wire is used for a number of things. Among others, for typical residential wiring it's used in 3-way light switches, mixed 240/120V loads (like a dryer), and in "split-wire" or "multi-wire" 120V circuits.
For general-purpose circuits #14 can handle 15A, #12 can handle 20A, and #10 can take 30A.
Chris
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"Chris Friesen" wrote

That is before the 20% derate factor.
When a c'bkr is in a panel, it is derated by 20% to handle the panel heat generated by adjacent c'bkrs..
Thus #14 can only handle 15*80%A on a continuous basis.
There ain't no free lunch.
Lew
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As another person responded, ground is inferred, so 12/2 is white/black/bare. 12/3 is white/black/red/bare, with the red being the other hot side for wiring 220.
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On Fri, 10 Aug 2007 14:19:22 -0700, snipped-for-privacy@gmail.com wrote:
[electrical question snipped]
You have just been introduced to the hazard of soliciting specialized advice on the internet. In the gaggle of answers so far, you have gotten some good information, some incorrectly applied information, some information given with good intentions but poorly stated, and some plain incorrect information. You've even had a couple of responses telling other responders that they are incorrect.
The big problem is, how do you know which is which? Unless you know the players, you can't. My drivel can look just as authoritative as anyone else's to someone relatively new to the Wreck. The fact is, there are about three or four posters here whose electrical information you can trust. Probably at the top of the list is Doug Miller. View anyone else's answers with suspicion. I'm surprised he hasn't posted already. I'm sure he will, however. He can cite the NEC chapter and verse. Hardly anyone else here can.
By the way, just to throw a monkey wrench in the works for all the oh-so-sure posters about the number of conductors in a cable--it wasn't so long ago ( in my lifetime and I can personally attest to it), that if you wanted a ground wire with your Romex (trade name for NMC or non metallic cable) you had to say "with ground." It was not implied. Granted that's no longer the case, but it does illustrate how gray an answer can sometimes be. Could be important is some old work.
My advice (and you can take this one to the bank) is don't be satisfied that you have all the information you need based on the answers you've received so far.
--
LRod

Master Woodbutcher and seasoned termite
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Speaking of useless answers. I went to some trade show years ago. I got a tote bag that might have said Copper is Proper. I cannot find the tote bag to see if that was the logo. Two points were made in the handout and it was geared towards commercial electricians. Well maybe one point. Copper flows electricity better than aluminum. 12 guage can be less expensive over the life of a building versus 14 guage due to lower power losses with the bigger wire. Equipment can run better with lower voltage drops. http://www.engineeringtoolbox.com/wire-gauges-d_419.html http://www.jlmwholesale.com/images/WIREGAUGE.pdf
Another anecdote which might be worthless. I have a friend who is certified in a lot of welding techniques. He has worked in power plants, oil rigs, made non destructive weld samples and seems to have a good bit of experience. He occasionally uses the small portable mig welder like I have in the garage. He has found that the little 120 volt welder does better with 10 guage service wire than it does with 12 guage service wire. I don't know how long the wire runs were when he was doing this experimenting but it reinforces the voltage drop. His eyes and skill with welds are better than my hack welds.
wrote:

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On Sat, 11 Aug 2007 12:41:38 GMT, Jim Behning
|Speaking of useless answers. I went to some trade show years ago. I |got a tote bag that might have said Copper is Proper. I cannot find |the tote bag to see if that was the logo. Two points were made in the |handout and it was geared towards commercial electricians. Well maybe |one point. Copper flows electricity better than aluminum. 12 guage can |be less expensive over the life of a building versus 14 guage due to |lower power losses with the bigger wire. Equipment can run better with |lower voltage drops. |http://www.engineeringtoolbox.com/wire-gauges-d_419.html |http://www.jlmwholesale.com/images/WIREGAUGE.pdf | |Another anecdote which might be worthless. I have a friend who is |certified in a lot of welding techniques. He has worked in power |plants, oil rigs, made non destructive weld samples and seems to have |a good bit of experience. He occasionally uses the small portable mig |welder like I have in the garage. He has found that the little 120 |volt welder does better with 10 guage service wire than it does with |12 guage service wire. I don't know how long the wire runs were when |he was doing this experimenting but it reinforces the voltage drop. |His eyes and skill with welds are better than my hack welds.
First of all, it's "gauge."
You don't need wire tables if you can remember that the resistance of a round copper conductor is given by:
DC resistance ( Ohm/1000' at 20 C.) = 10 ^ (0.1 * AWG - 1)
where AWG is American Wire Gauge.
The resistivity of aluminum is approx 1.52 times copper.
So for a 20A run using 12 AWG, 100' long (200' of wire) the copper loss is ~45 W.
For the same run in aluminum the loss is ~69 W.
The difference in efficiency (power delivered to load / power into wire) is 98.1% vs. 97.1%.
Is this somthing to get excited about?
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