If you wire for higher ampacity, then may as well install appropriately
sized breakers and outlets, etc., at the time. Otherwise, unless wasted
the extra money for the higher-rated outlets until that unforeseen maybe
never to happen time in the future, placing simply a larger breaker may
be fine for the wiring itself but not for the outlets, etc., ...
True but I was thinking of being able to add more outlets to the same line.
Example when I bought my last house there was one outlet along the wall were
I wanted to put my entertainment center I had to use 2 power strips. No big
deal there because nothing was drawing much power and very few of the items
were on at any one time. But what if in the future things need more power?
I'm guessing they will. Its a lot easier to put an outlet or two on an
existing circuit than it is to run an entire new line from the breaker box.
Who know what we will need in 10 years. Its a bit more than 10 years old
but the house mom lives in had a total of 6 fuses when it was built!! I
think when we remodeled it we added 6 more circuits, with fuses so you can
tell that's been a while ago. :)
I might change my mind when I start building. But right now its going to be
an over wired, concrete dome with metal studs and fiberglass backed
wallboard. I'm a bit paranoid about fire so there will be very few
flammable building materials used in it.
Yeah, right. My uncle did that when he built his house back in the
'60s. He ran 12 ga to every single device in the house--receptacles,
switches, lights. At the tiime I thought it was a good idea--after
all, it's only one size up, right?
Said he'd never do it again. He nearly crippled himself wiring all
those living room receptacles designed to accommodate a reading lamp
and the bedroom receptacles designed for an alarm clock. To what
purpose? Don't believe me? Go stuff a half dozen boxes with 12 gauge
wire and wire the receptacles. Then do the same with 14 guage wire.
The difference in effort is not trivial.
The shop, on the other hand, is a supportable venture in the larger
wire department. However, unless you're looking at something
significantly greater than say 1000 ft^2 and without a nearby or en
suite load center, you gain virtually nothing by going up a wire size.
If you're running 3HP machines (kind of a regular, home shop size
motor) you don't need any more than a 20A circuit at 240V. If you're
running 5HP you have to go to 30A anyway (and it's more than enough)
so why would you need to go to 40A?
You can't be serious. It's not nearly as difficult as finding a 15 or
20 amp receptacle into which you can stuff that 8 gauge wire.
You'd be hard pressed working 10 gauge (30A) wire around very many
boxes before you realized what a load of an idea that was. Forget 8
Dumb idea #3. The difference in cost between a 20A breaker and 30A
breaker is negligible (they're virtually the same in the Square D QO
line). If you really were commited to running 10 gauge wire throughout
the house (ignoring, for the moment, the difficulty in working it and
the utter lack of need for it) why would you not go ahead and put 30A
All this talk about sizing up electrical circuits is roughly the same
as knot tying by someone who doesn't know how to tie knots--if one
loop is good, two or three must be two or three times better, right?
Your uncle would be right at home in most of the municipalities around here
... along with the requirement for 5/8" drywall, the minimum wire size
allowed here for _any_ circuit, lights included, is 12ga.
Nonsense. Except on very long runs, bigger wire provides no advantages at all,
and does provide significant disadvantages:
a) higher cost
b) greater difficulty in installation
c) difficulty in finding compatible receptacles (for example, try finding a
15A rated receptacle that will accept AWG8 wire)
d) the larger the wire, the fewer of them the Code allows you to put in a box.
This purpose is achieved much more easily, and at considerably lower cost, by
keeping the wire size the same and increasing the number of circuits.
Nonsense again. The risk of electrical fire is not significantly greater using
AWG12 wire on a 20A breaker, compared to using AWG8 -- and in fact, you'd
probably be creating a substantial risk of fire by attempting to connect a
standard receptacle to conductors that are too large to fit under the screw
terminals. Sure, you can pigtail the connections -- let me know when you're
getting ready to wire up those receptacles. I want to come watch you stuff
the wires back in the box; I could use a few laughs.
And then I'll phone the local electrical inspector. "Wire that will carry 40
amps or so" is AWG8 or larger. You might want to consult Table 314.16(A) in
the NEC to see how many AWG8 conductors the Code allows you to put in a
standard device box. (Hint: except with the largest device box available, it's
not enough to supply a receptacle -- and forget about feeding through to
another receptacle, or using anything larger than AWG8.)
Nonsense yet again. What, exactly, do you plan to "upsize" to, anyway? It's a
Code violation to put a 20A receptacle on a circuit protected by anything but
a 20A breaker. The larger wire serves no purpose at all.
Doug Miller (alphageek at milmac dot com)
Just curious.....aren't most electrical fires related to junctions,
switches, receptacles and things plugged into them? In other words aren't
strait wire runs the least problematic of any potential electrical fault as
On Mon, 13 Aug 2007 17:19:43 GMT, email@example.com (Doug Miller)
#12 thhn cu wire is actually rated for about 35 amps. The
restriction to 20 amps is mainly based on the rating of the terminal
on the CB. You may use the higher ampacity ratings before taking your
derating but still can't have over a 20 amp breaker.
That's part of it, but not the only reason. 10, 12, and 14 gauge wires are the
sizes most commonly used in residential circuits. The allowable overcurrent
protection is set by the Code at a value significantly under the actual
ampacity of the wires to reduce the risk of fire from overloading a circuit.
Which means that the higher ampacity ratings are, for all practical purposes,
Doug Miller (alphageek at milmac dot com)
On Sat, 18 Aug 2007 13:36:19 GMT, firstname.lastname@example.org (Doug Miller)
Shows how bad my memory is getting.
This is true for residential work generally, but in commercial work
where you might be derating for continuous load, number of conductors
in pipe, as well as ambient temperature it can make a difference.
That was my theory with my LAN. When I was initially building it, I
decided to go with Cat 5 cable capable of 100 mbs, and only get a hub
capable of 10 mbs. When the prices came down on 100 mbs switches, all I
had to do was unplug one and plug in the new one.
Wise is the man who attempts to answer his question before asking it.
To email me directly, send a message to puckdropper (at) fastmail.fm
An entirely different kettle of fish. The wire you used is part of the
standard for both speeds, and maybe others, and works pretty easily for
the setup you describe.
Which is pretty much exactly what was discussed back in the early to
mid-90's when all of this started to come together...
who did the same thing, really...
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.
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
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
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
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%A 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
"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
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.
Doug Miller (alphageek at milmac dot com)
Name plate ratings of molded case thermal-magnetic c'bkrs are for bkrs in
As soon as the bkr is placed in an enclosure, detating applies.
Take your meds and go read your code book again, this time try to understand
what you read.
Three (3) hours doesn't meet the definition of "continuous" in my world.
The definition of "continuous" in your world, wherever that may be, is
irrelevant. The only meaningful definition, for purposes of determining Code
compliance, is that provided by Article 100 of the NEC: "a load where the
maximum current is expected to continue for 3 hours or more."
And *that* is where the 20% derating applies: to continuous loads as defined
by the NEC. Not as defined by Lew.
Now go take your meds and read your code book again. This time try to
understand what you read.
Doug Miller (alphageek at milmac dot com)
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.
On Aug 10, 5:19 pm, email@example.com wrote:
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.
Resulting from Google Search using "Home Electrical Wiring Basics."
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
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, firstname.lastname@example.org wrote:
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