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?
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.
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.
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
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.
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.
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.
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).
"10/2 and 12/2 only have 2 wires."
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.
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
For general-purpose circuits #14 can handle 15A, #12 can handle 20A, and
#10 can take 30A.
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.
On Fri, 10 Aug 2007 14:19:22 -0700, firstname.lastname@example.org 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.
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.
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.
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.
|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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