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
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.
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
"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%=12A on a continuous basis.
There ain't no free lunch.
Lew
That's incorrect. The second number is the number of conductors. Ground isn't counted as a "conductor".
Chris
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.
No, I think that when the say "conductor", they mean insulated conductor. 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
All of the wires in my 10/3 are insulated.
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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
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.
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.
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.
It's unusual to find ground insulated in a romex type wire. Are you quite certain of this Leon?
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.
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!
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.
Rules of thumb. #14 wire takes a 15 amp breaker #12 wire takes a 20 amp breaker Ordinary 120 Volt wall sockets are rated for 15 or 20 amps and will accept #14 or #12 wire. I suppose it's possible to jam #10 wire under the screws but I wouldn't do it myself. Based on this, I wire my branch circuits with #12.
Connect black to brass, white to chrome.
Treat both sides of the AC line (black and white) as hot. Some other electrician may have forgotten about black to brass and white to chrome somewhere else in the building wiring.
Ground every piece of metal you can touch.
David Starr
|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. |
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?
I'll take that one step further. If a guy has to ask the difference between 10/2, 10/3. 12/2 etc... WTF is he doing wiring his shop?
For chrissakes, call somebody who knows and who has the certification and insurance!!
And GET A FARKING PERMIT!!
(Yes, yes, I know, I know... there are many here who have the knowledge and confidence to do that kind of work themselves, but when questions indicate a complete and total ignorance of the topic at hand.........)
rYou have always heard there are no stupid questions. Maybe the questions were asked for reference. To see what others had done when there shop was wired. I think it was a legitimate question asking the difference between the wires. If he is to have someone wire the shop are all electricians going to wire with 12/2 on 220 and 10/2 on 110? Knowledge is a good thing and being able to tell the electrician what you want can only make the shop that much better.
John
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