Folks -
I'm back... Now it's a wiring question. I'd like to run a string of outlets
at benchtop height, and run two circuits. I'll put a pair of outlets in
each box, 1 on each circuit. Can I safely run 12/3 for a pair of 20 amp
circuits using a common neutral (white) and ground? I'd run the red wire
(marked black) to one outlet and the black to the other. The two outlets
would share the white wire, along with the grounds.
At the panel, I'd have the red (marked black) wire going to one CB and the
black one to a separate CB. If I can do this, I'd have to string way less
NM... Would this be a violation of code? Is this safe?
I know, I know... call an electrician or an EE... I'm just trying to get a
little help here....
Thanks in advance!
John Moorhead
Patriarch -
I agree, the issue isn't cost... It's time and effort... If I could run a
single 12/3 and get two circuits, it would save another run... But after
reading all of these posts, I've taken the 12/3 back and will play it safer
and have two complete separate runs for 20a circuits using 12/2 and GFCI's
with other outlets connected "downstream"
Believe me... I haven't skimped on ANYTHING with this project - ask my
wallet!
John
On Fri, 03 Dec 2004 18:27:03 +0000, LRod <[email protected]> wrote:
> On Fri, 03 Dec 2004 16:56:53 GMT, "John Moorhead"
><[email protected]> wrote:
>
>>Folks -
>>
>>I'm back... Now it's a wiring question. I'd like to run a string of outlets
>>at benchtop height, and run two circuits. I'll put a pair of outlets in
>>each box, 1 on each circuit. Can I safely run 12/3 for a pair of 20 amp
>>circuits using a common neutral (white) and ground? I'd run the red wire
>>(marked black) to one outlet and the black to the other. The two outlets
>>would share the white wire, along with the grounds.
>>
>>At the panel, I'd have the red (marked black) wire going to one CB and the
>>black one to a separate CB. If I can do this, I'd have to string way less
>>NM... Would this be a violation of code? Is this safe?
>
> So far the answers you've gotten are either wrong or way wrong.
>
> Shared neutral is certainly legal in the U.S. For those pontificating
> on how it's allegedly unsafe, the two hots MUST be fed from a duplex
> breaker, which does two things: it ensures that both feeds are on
> opposite buses which means that the neutral currents for each branch
> are 180° out of phase and thus subtractive, and it ensures that when
> the breaker is tripped (intentionally or otherwise) there are no hot
> leads in a box with two separate branches in it.
>
> So the short answer is, yes, you can do that.
>
I didn't assert "Unsafe" but rather "I'd heard it was Canadian practice
but never heard of it being done in the States."
I've certainly never seen it here in NJ.
OTOH, a duplex breaker will certainly be safe, so there you (or he)
goes.
"Doug Winterburn" <[email protected]> wrote in message news:[email protected]...
> On Fri, 03 Dec 2004 18:53:58 +0000, Bob wrote:
>
> >
> > "john" <[email protected]> wrote in message
> > news:[email protected]...
> >> It is simply a multiwire circuit. As long as you use a 240v breaker for
> >> the two circuits, it fine; maybe.
> >
> > I disagree. You are allowing 40 amps (2 * 20) across a single conductor
> > (the neutral) by sharing it with two single phase 20 amp circuits.
>
> I disagree. As long as each breaker is on the opposite hot as in any
> 240V circuit, the total neutral load will never exceed the current draw of
> the largest circuit load. If each circuit was drawing an equal load, the
> neutral load would be zero.
>
> -Doug
Your analysis is absolutely correct.
--
Al Reid
How will I know when I get there...
If I don't know where I'm going?
In article <[email protected]>,
LRod <[email protected]> wrote:
>On Fri, 03 Dec 2004 16:56:53 GMT, "John Moorhead"
><[email protected]> wrote:
>
>>Folks -
>>
>>I'm back... Now it's a wiring question. I'd like to run a string of outlets
>>at benchtop height, and run two circuits. I'll put a pair of outlets in
>>each box, 1 on each circuit. Can I safely run 12/3 for a pair of 20 amp
>>circuits using a common neutral (white) and ground? I'd run the red wire
>>(marked black) to one outlet and the black to the other. The two outlets
>>would share the white wire, along with the grounds.
>>
>>At the panel, I'd have the red (marked black) wire going to one CB and the
>>black one to a separate CB. If I can do this, I'd have to string way less
>>NM... Would this be a violation of code? Is this safe?
>
>So far the answers you've gotten are either wrong or way wrong.
Agree. Even after this excellent post, a whole stream of wrong
answers kept coming. Fortunately, there were also a few right answers.
Rule #1: DO NOT TRUST SOME RANDOM POSTER ON USENET. For all you know,
we might be all homicidal maniacs. Furthermore, not all localities
use just the NEC, some have additional electric codes. Call either
the building inspector in your locality, or talk to a real
(experienced and licensed) electrician in your area.
That having been said ...
>Shared neutral is certainly legal in the U.S. For those pontificating
>on how it's allegedly unsafe, the two hots MUST be fed from a duplex
>breaker, which does two things: it ensures that both feeds are on
>opposite buses which means that the neutral currents for each branch
>are 180° out of phase and thus subtractive, and it ensures that when
>the breaker is tripped (intentionally or otherwise) there are no hot
>leads in a box with two separate branches in it.
Completely agree. More discussion of GFCI below, though.
>The long answer is I don't like shared neutral circuits and avoid them
>like the plague. Call it personal prejudice but you have to make sure
>you have a continuous neutral (all pigtails to the receptacles) so
>that you don't wind up with 240V across the devices if the neutral is
>lost.
Partially agree, partially disagree. Agree: If you use them to feed
the two halves of a duplex receptacle, I think they are dangerous.
Because (a) there are 240V across components that are physically very
close together, and (b) all you need is one wire to come loose, and
you have 240V across the load.
On the other hand, if you use them to feed separate receptacles, I
think they are acceptable - they end up being a way to save wire and
time (it is easier to string one 12-3 than to string two 12-2 next to
each other). Just use extra care in wiring the neutrals (*) together,
to make sure they don't come undone.
Even better: They make raceways with built-in outlets (wiremold is a
popular brand). This stuff looks like a metal tray, about 1" square,
and it has an outlet ever few inches or every foot. This is ideal for
feeding power at counter height in a shop. And you can get it
pre-wired for two circuits: One neutral conductor, one ground
conductor, and two hot conductors. This makes a perfect match to an
edison- or multiwire circuit with a dual-pole 20A breaker: With very
little work, you have two 20A circuits everywhere in your shop, and
you'll never run out of outlets. This type of multioutlet assembly
(technical term for the wiremold stuff) has to be fed from an edison-
or multiwire circuit. This is what I have installed in my basement
shop.
The only real problem is how to add GFCIs. One option is to use two
(or more) individual GFCI outlets at the endpoint of the edison
circuit. The problem is: if you want to add the "load" connection of
the GFCI outlet, you must never merge the neutrals back together. So
behind the GFCI, the circuit is no longer an edison- or
multiwire-circuit. If you want to use multi-outlet assemblies (like
the wiremold stuff), or a split duplex receptacle (one outlet on each
of the circuits), there is no simple way to add GFCIs. You can't just
put two GFCIs next to each other, and feed through them, because
merging the two neutrals back together is a no-no (not just illegal,
it will just plain not work). In this case, you have to use stronger
medicine: A 2-pole 240V GFCI 20A breaker in the panel. Those exist,
but they are very rarely used, and therefore pretty hard to find (the
borg doesn't stock them). The real bad news is the cost: I paid a
little over $100 for the GFCI breaker. So if you need GFCI protection
(basement, garage, outdoors, etc.), this negates any potential cost
saving.
(*) The term "neutral" is not used in the code for 240V circuits, or
edison- or multi-wire circuits. Instead, it is called the "grounded
conductor" (a.k.a. the white wire). Don't confuse that with the
"grounding conductor" (a.k.a. the green wire). The colloquial term
"neutral" is much clearer, and in common use. Unfortunately, to
further confuse the issue, the code uses the term "neutral" for
certain cases of three-phase circuits.
--
The address in the header is invalid for obvious reasons. Please
reconstruct the address from the information below (look for _).
Ralph Becker-Szendy _firstname_@lr_dot_los-gatos_dot_ca.us
On Fri, 03 Dec 2004 16:56:53 GMT, "John Moorhead"
<[email protected]> wrote:
>Folks -
>
>I'm back... Now it's a wiring question. I'd like to run a string of outlets
>at benchtop height, and run two circuits. I'll put a pair of outlets in
>each box, 1 on each circuit. Can I safely run 12/3 for a pair of 20 amp
>circuits using a common neutral (white) and ground? I'd run the red wire
>(marked black) to one outlet and the black to the other. The two outlets
>would share the white wire, along with the grounds.
>
>At the panel, I'd have the red (marked black) wire going to one CB and the
>black one to a separate CB. If I can do this, I'd have to string way less
>NM... Would this be a violation of code? Is this safe?
So far the answers you've gotten are either wrong or way wrong.
Shared neutral is certainly legal in the U.S. For those pontificating
on how it's allegedly unsafe, the two hots MUST be fed from a duplex
breaker, which does two things: it ensures that both feeds are on
opposite buses which means that the neutral currents for each branch
are 180° out of phase and thus subtractive, and it ensures that when
the breaker is tripped (intentionally or otherwise) there are no hot
leads in a box with two separate branches in it.
So the short answer is, yes, you can do that.
The long answer is I don't like shared neutral circuits and avoid them
like the plague. Call it personal prejudice but you have to make sure
you have a continuous neutral (all pigtails to the receptacles) so
that you don't wind up with 240V across the devices if the neutral is
lost.
Wire is relatively cheap. No matter how big your shop (well, up to a
reasonable size, anyway), you'd be hard pressed to add $100 to the
bill by wiring two completely separate circuits. Of course if you do
it that way I wouldn't recommend putting receptacles fed by two
different circuits in the same box. Same issue as with the shared
neutral circuit if a duplex breaker weren't used.
- -
LRod
Master Woodbutcher and seasoned termite
Shamelessly whoring my website since 1999
http://www.woodbutcher.net
In article <[email protected]>,
Doug Miller <[email protected]> wrote:
>In article <[email protected]>, "Mike
>Marlow" <[email protected]> wrote:
>>
>>"U-CDK_CHARLES\Charles" <"Charles Krug"@aol.com> wrote in message
>>news:xA1sd.42$IB6.28@trndny06...
>
>>> Also if it's in a garage, the GFCI will sense the imbalanced current and
>>> trip.
>>
>>I don't see how this would happen. The potential between neutral and ground
>>are the same as if you had run a separate neutral.
>>
>GFCIs operate by sensing the currents on the hot and neutral. If they differ
>by more than 20ma, the GFCI opens -- the point being that if the currents are
>not the same, then there must be leakage somewhere.
>
>Consider this:
>
>red -----------------********
> * *
>white -----------------* GFCI *------------***************
>(neutral) * * * insert 120V *
> ******** * load of your*
> * choice here *
>black -------------------------------------***************
>
>As soon as a load of more than 20ma is applied between the black and the
>white, the GFCI will trip, because the current in the white wire does not
>balance the current in the red wire.
"Yeahbut" applies. For U.S.A. installations, it _ain't_ wired that way.
In the case of GFCI outlets, the wiring is:
red -----------------********
(1) * *
white ------------+----* GFCI *
(neutral) | * *
| ********
|
+------------------------***************
* insert 120V *
* load of your*
* choice here *
black -------------------------------------***************
(1) is either a 'wrap around' the screw on the GFCI, or a *continuous*
strand from the breaker box, towards the 'load of your choice' with a
'pigtailed' section going to the GFCI. Has to be built such that you
_cannot_ disconnect the neutral going to 'a different location'.
If the current level on red and white, _at_the_GFCI_ isn't the same, then
something that is coming 'in' on the 'red' lead is going 'out' somewhere
other than the 'white' lead. And the GFCI triggers.
This is _independent_ of what is happening with the '120V load of your choice'.
What I have in my kitchen is =precisely= the above, where the 'load of your
choice' is _another_ GFCI outlet. I run _grossly_ 'unbalanced' loads
across the two circuits all the time -- like 1800 watt draw on one circuit
and *zero* on the other. Neither of the GFCIs trip.
This wiring was done per a city electrical permit, under the supervision
of a licensed electrician with going on *60* years experience, _and_ blessed
by the city electrical inspector.
In article <[email protected]>,
Doug Miller <[email protected]> wrote:
>In article <[email protected]>,
>[email protected] (Robert Bonomi) wrote:
>>In article <[email protected]>,
>>Doug Miller <[email protected]> wrote:
>>>In article <[email protected]>, "Mike
>>>Marlow" <[email protected]> wrote:
>>>>
>>>>"U-CDK_CHARLES\Charles" <"Charles Krug"@aol.com> wrote in message
>>>>news:xA1sd.42$IB6.28@trndny06...
>>>
>>>>> Also if it's in a garage, the GFCI will sense the imbalanced current and
>>>>> trip.
>>>>
>>>>I don't see how this would happen. The potential between neutral and ground
>>>>are the same as if you had run a separate neutral.
>>>>
>>>GFCIs operate by sensing the currents on the hot and neutral. If they differ
>>>by more than 20ma, the GFCI opens -- the point being that if the currents are
>>>not the same, then there must be leakage somewhere.
>>>
>>>Consider this:
>>>
>>>red -----------------********
>>> * *
>>>white -----------------* GFCI *------------***************
>>>(neutral) * * * insert 120V *
>>> ******** * load of your*
>>> * choice here *
>>>black -------------------------------------***************
>>>
>>>As soon as a load of more than 20ma is applied between the black and the
>>>white, the GFCI will trip, because the current in the white wire does not
>>>balance the current in the red wire.
>>
>>"Yeahbut" applies. For U.S.A. installations, it _ain't_ wired that way.
>
>Not by someone who understands what he's doing, anyway, but it certainly *can*
>be wired that way. Doesn't mean it's right, of course... and anyone who
>doesn't understand how GFCIs work, and how current flows in an Edison circuit,
>is going to be left scratching his head wondering why the GFCI on leg 'A'
>trips as soon as he flips on a light switch on leg 'B'.
Gotta add "incapable of reading _and_following_ the directions" to the skill-
set. <grin>
All the instructions I've seen were _quite_ explicit about using the 'load'
side terminals on a GFCI outlet only for wiring to a downstream isolated outlet.
That you had to run _both_ wires from the 'load' side of the GFCI to the
other outlets. In fact, as they come out of the box, both the load side
fittings are taped over (single piece of tape), so you -can't- 'accidentally
connect something up to them.
In article <[email protected]>,
John Moorhead <[email protected]> wrote:
>Folks -
>
>I'm back... Now it's a wiring question. I'd like to run a string of outlets
>at benchtop height, and run two circuits. I'll put a pair of outlets in
>each box, 1 on each circuit. Can I safely run 12/3 for a pair of 20 amp
>circuits using a common neutral (white) and ground? I'd run the red wire
>(marked black) to one outlet and the black to the other. The two outlets
>would share the white wire, along with the grounds.
>
>At the panel, I'd have the red (marked black) wire going to one CB and the
>black one to a separate CB. If I can do this, I'd have to string way less
>NM... Would this be a violation of code? Is this safe?
>
>I know, I know... call an electrician or an EE... I'm just trying to get a
>little help here....
First question: *WHERE* are you? Code _does_ vary, by locale, on whether
things like this are allowed.
Comment: this 'two hot, one neutral' wiring is called an 'Edison circuit'.
*IS* generally allowed, _as_long_as_ you make sure that the two hot wires
go to *different* phases of the main supply.
You do -not- need to 'tag' the red wire as black, btw. anything _other_
_than_ one of the 'reserved' colors (white, green, bare) is presumed to
be a 'hot' lead.
I would *NOT* recommend running "12/3" wire. Pull _individual_ wires --
even when pulled at the same time, they go around corners *easier* than
the multi-wire cable. You'll likely find that the individual wires are
less expensive than the multi-wire cable, too.
In article <[email protected]>, igor <[email protected]> wrote:
>On Fri, 03 Dec 2004 18:56:12 +0000, [email protected] (Robert
>Bonomi) wrote:
>
>
>>You do -not- need to 'tag' the red wire as black, btw. anything _other_
>>_than_ one of the 'reserved' colors (white, green, bare) is presumed to
>>be a 'hot' lead.
>
>I think that is correct. OTOH, sometimes one must tag a white wire as
>black (hot), such as in a 2-wire (plus ground) 240 circuit or in some 3-way
>switch configs.
Right. Technically, it doesn't even have to be marked black; it could be
marked any color _other_than_ white, gray, green, or green with a yellow
stripe.
--
Regards,
Doug Miller (alphageek-at-milmac-dot-com)
Get a copy of my NEW AND IMPROVED TrollFilter for NewsProxy/Nfilter
by sending email to autoresponder at filterinfo-at-milmac-dot-com
You must use your REAL email address to get a response.
In article <[email protected]>,
Bob <[email protected]> wrote:
>
>"Doug Miller" <[email protected]> wrote in message
>news:[email protected]...
>
>> It is perfectly safe, and does not violate code, as long as:
>> a) the two hot conductors are on opposite legs of a 240V service, *and*
>> b) a *single* disconnecting means will disconnect *both* of them at once.
>> Both of these criteria are easily satisfied by using a standard two-pole
>> breaker: the two sides are necessarily on opposite legs, and one handle
>> disconnects them both at once.
>
>Doug, you seem to know what you are talking about. What's your experience
>with how often this is actually done? It seems to me that, though legal and
>safe, someone might forget how this is setup and rearrange breakers/wiring
>in the future, creating an unsafe situation. Are there any requirements for
>tagging such a configuration?
'Standard practice' is to run _different_ colors of 'hot' wire. With
all the wiring on a given phase being the same color. I use different
colors for each hot phase, _and_ unique colors for any 'switched' hot
leads. If I have 3 switched leads in the same place, they'll be three
different colors -- e.g. 'yellow', 'pink', 'blue'. With this kind of
set-up, if you find a 'non-red/black' - neutral pair, you *know* you can't
_trust_ that the *circuit* is dead, just because there's no power across
the pair. Gotta find the switch (or switches!!) first. and check _there_.
Any competent electrician, does any breaker 're-arranging' only _within_ a
single color. Or *thoroughly* investigates the details, and then 'marks'
*both*ends* of any wires that get 'moved' to a different phase. *AFTER*
having made sure that neutral load currents are _not_ exceeded.
This is practically 'no-brainer' stuff for a professional. The amateur
that doesn't understand stuff at this level, should *not* be messing in
the panel. <grin>
This is also why =many= communities have a 'basic wiring' test that you
have to pass, _as_a_homeowner_, before you can get a permit for 'do it
yourself' work. These exams are _not_ difficult -- their primary purpose
is to ensure that you know enough to not to anything 'dangerously stupid'
in _residential_ wiring.
In article <[email protected]>, [email protected] (Robert Bonomi) wrote:
>In article <[email protected]>,
>Doug Miller <[email protected]> wrote:
>>In article <[email protected]>, "Mike
>>Marlow" <[email protected]> wrote:
>>>
>>>"U-CDK_CHARLES\Charles" <"Charles Krug"@aol.com> wrote in message
>>>news:xA1sd.42$IB6.28@trndny06...
>>
>>>> Also if it's in a garage, the GFCI will sense the imbalanced current and
>>>> trip.
>>>
>>>I don't see how this would happen. The potential between neutral and ground
>>>are the same as if you had run a separate neutral.
>>>
>>GFCIs operate by sensing the currents on the hot and neutral. If they differ
>>by more than 20ma, the GFCI opens -- the point being that if the currents are
>>not the same, then there must be leakage somewhere.
>>
>>Consider this:
>>
>>red -----------------********
>> * *
>>white -----------------* GFCI *------------***************
>>(neutral) * * * insert 120V *
>> ******** * load of your*
>> * choice here *
>>black -------------------------------------***************
>>
>>As soon as a load of more than 20ma is applied between the black and the
>>white, the GFCI will trip, because the current in the white wire does not
>>balance the current in the red wire.
>
>"Yeahbut" applies. For U.S.A. installations, it _ain't_ wired that way.
Not by someone who understands what he's doing, anyway, but it certainly *can*
be wired that way. Doesn't mean it's right, of course... and anyone who
doesn't understand how GFCIs work, and how current flows in an Edison circuit,
is going to be left scratching his head wondering why the GFCI on leg 'A'
trips as soon as he flips on a light switch on leg 'B'.
--
Regards,
Doug Miller (alphageek-at-milmac-dot-com)
Get a copy of my NEW AND IMPROVED TrollFilter for NewsProxy/Nfilter
by sending email to autoresponder at filterinfo-at-milmac-dot-com
You must use your REAL email address to get a response.
"Swingman" <[email protected]> wrote in message
news:[email protected]...
> "John Moorhead" wrote in message
>
> > I'm back... Now it's a wiring question. I'd like to run a string of
> outlets
> > at benchtop height, and run two circuits. I'll put a pair of outlets in
> > each box, 1 on each circuit. Can I safely run 12/3 for a pair of 20 amp
> > circuits using a common neutral (white) and ground? I'd run the red
wire
> > (marked black) to one outlet and the black to the other. The two
outlets
> > would share the white wire, along with the grounds.
> >
> > At the panel, I'd have the red (marked black) wire going to one CB and
the
> > black one to a separate CB. If I can do this, I'd have to string way
less
> > NM... Would this be a violation of code? Is this safe?
> >
> > I know, I know... call an electrician or an EE... I'm just trying to
get
> a
> > little help here....
>
> What you are looking at is a "split circuit" receptacle. It's been
perfectly
> legal in a number of locale's, but I am not sure what the latest NEC says
> about it.
>
> Two caveats that are generally required to do it:
>
> 1. You must cut or remove the metal bridge on the duplex receptacles
>
> 2. It is generally required that you must use two, two pole circuit
brkr's,
> with the two circuit brkr's "tied" together so that if one trips, they
both
> trip.
>
> In any event, the terminology you want to use with your building
inspection
> department is "split circuit receptacle".
>
Look at it again Swingman - he doesn't want to split an outlet, he wants two
duplexes together in a double box that have their own hots, but share a
neutral and a ground.
--
-Mike-
[email protected]
"Mike Marlow" <[email protected]> wrote in message
news:[email protected]...
>
>
> I don't see how this would happen. The potential between neutral and
> ground
> are the same as if you had run a separate neutral.
>
A GFCI works by detecting a difference in the amount of current flowing
though the hot conductor and the neutral. I think this is what he is
referring to. The neutral will carry the sum of the two branch circuits.
Frank
"U-CDK_CHARLES\Charles" <"Charles Krug"@aol.com> wrote in message
news:xA1sd.42$IB6.28@trndny06...
> On Fri, 03 Dec 2004 17:35:51 GMT, John Moorhead
> <[email protected]> wrote:
> > Nope - I'm in Northern California... Well, I *do* want alternate
> > circuits... The reason for using a single run of 12/3 is that I
wouldn't
> > have to run an additional separate length of wire - everything would be
in
> > the one cable. Sorry if my post didn't make that clear...
> >
> > John
>
> I'm reasonably certain that's not allowed in the US.
Seems to me that shared neutrals are allowed under some circumstances, but I
can't recall if you have to downgrade the cirucuit when doing so. Wait for
some of the electricians to weigh in on this one.
>
> In any case, the lone neutral lacks the capacity for both circuits.
> Also if it's in a garage, the GFCI will sense the imbalanced current and
> trip.
>
>
I don't see how this would happen. The potential between neutral and ground
are the same as if you had run a separate neutral.
--
-Mike-
[email protected]
"John Moorhead" wrote in message
> at benchtop height, and run two circuits. I'll put a pair of outlets in
> each box, 1 on each circuit.
To get a precise answer, it is important that you clarify this. Do you want
to be able to plug in two, or four, plugs in the box?
--
www.e-woodshop.net
Last update: 11/06/04
In article <[email protected]>, "Swingman" <[email protected]> wrote:
>"John Moorhead" wrote in message
>
>> I'm back... Now it's a wiring question. I'd like to run a string of
>outlets
>> at benchtop height, and run two circuits. I'll put a pair of outlets in
>> each box, 1 on each circuit. Can I safely run 12/3 for a pair of 20 amp
>> circuits using a common neutral (white) and ground? I'd run the red wire
>> (marked black) to one outlet and the black to the other. The two outlets
>> would share the white wire, along with the grounds.
>>
>> At the panel, I'd have the red (marked black) wire going to one CB and the
>> black one to a separate CB. If I can do this, I'd have to string way less
>> NM... Would this be a violation of code? Is this safe?
>>
>> I know, I know... call an electrician or an EE... I'm just trying to get
>a
>> little help here....
>
>What you are looking at is a "split circuit" receptacle. It's been perfectly
>legal in a number of locale's, but I am not sure what the latest NEC says
>about it.
>
>Two caveats that are generally required to do it:
>
>1. You must cut or remove the metal bridge on the duplex receptacles
Not if he's using two duplex receptacles in each box, as it appears he
intends. And even if he's using one duplex receptacle per box, with each half
on a different phase, he still needs to remove the bridge *only* on the hot
side.
>
>2. It is generally required that you must use two, two pole circuit brkr's,
>with the two circuit brkr's "tied" together so that if one trips, they both
>trip.
Ummm.... no. That would be *one* two-pole circuit breaker.
>
>In any event, the terminology you want to use with your building inspection
>department is "split circuit receptacle".
Not necessarily. That's one duplex receptacle, with each half on a different
leg. It sounded to me like he intended each box to have two duplex
receptacles, with each duplex on a different leg.
--
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In article <[email protected]>, "Frank Ketchum" <[email protected]> wrote:
>
>"John Moorhead" <[email protected]> wrote in message
>news:[email protected]...
>> Folks -
>>
>> I'm back... Now it's a wiring question. I'd like to run a string of
>> outlets at benchtop height, and run two circuits. I'll put a pair of
>> outlets in each box, 1 on each circuit. Can I safely run 12/3 for a pair
>> of 20 amp circuits using a common neutral (white) and ground? I'd run the
>> red wire (marked black) to one outlet and the black to the other. The two
>> outlets would share the white wire, along with the grounds.
>>
>
>I do not believe this is allowed by the NEC. If you think about it, each of
>the two hots will be on 20 amp breakers and will be current limited to 20
>amps. The neutral will have to carry the sum of the two circuits, or
>potentially 40 amps back to the panel. 12 AWG wire is not rated for 40
>amps! You may be allowed to do this if you derate the circuit, but I doubt
>you will want to do this.
Geez. Here we go again.
Yes, it is allowed by the NEC, as long as the two hot conductors are on
opposite legs of the 240V service, and a single disconnect, disconnects them
both. This is easily implemented by using a single double-pole breaker. With
the two hots on opposite legs, the current in the neutral is the *difference*
of the currents in the individual hot conductors, *not* the sum, and thus can
never exceed 20 amps. There just isn't a problem with doing this.
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"Doug Winterburn" <[email protected]> wrote in message
news:[email protected]...
> On Fri, 03 Dec 2004 18:53:58 +0000, Bob wrote:
>
> >
> > "john" <[email protected]> wrote in message
> > news:[email protected]...
> >> It is simply a multiwire circuit. As long as you use a 240v breaker
for
> >> the two circuits, it fine; maybe.
> >
> > I disagree. You are allowing 40 amps (2 * 20) across a single conductor
> > (the neutral) by sharing it with two single phase 20 amp circuits.
>
> I disagree. As long as each breaker is on the opposite hot as in any
> 240V circuit, the total neutral load will never exceed the current draw of
> the largest circuit load. If each circuit was drawing an equal load, the
> neutral load would be zero.
You are correct. My statement only applies if both branches come off the
same leg.
Bob
In article <[email protected]>, "John Moorhead" <[email protected]> wrote:
>Folks -
>
>I'm back... Now it's a wiring question. I'd like to run a string of outlets
>at benchtop height, and run two circuits. I'll put a pair of outlets in
>each box, 1 on each circuit. Can I safely run 12/3 for a pair of 20 amp
>circuits using a common neutral (white) and ground? I'd run the red wire
>(marked black) to one outlet and the black to the other. The two outlets
>would share the white wire, along with the grounds.
>
>At the panel, I'd have the red (marked black) wire going to one CB and the
>black one to a separate CB. If I can do this, I'd have to string way less
>NM... Would this be a violation of code? Is this safe?
It is perfectly safe, and does not violate code, as long as:
a) the two hot conductors are on opposite legs of a 240V service, *and*
b) a *single* disconnecting means will disconnect *both* of them at once.
Both of these criteria are easily satisfied by using a standard two-pole
breaker: the two sides are necessarily on opposite legs, and one handle
disconnects them both at once.
It's not necessary to mark the red wire black, as red wires are assumed to be
hot anyway. The conductor color requirements in the code are pretty simple:
Ground: bare, green, or green with a yellow tracer
Neutral: white or gray
Hot: Anything else.
>
>I know, I know... call an electrician or an EE... I'm just trying to get a
little help here....
You're fine.
--
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"John Moorhead" wrote in message
> I'm back... Now it's a wiring question. I'd like to run a string of
outlets
> at benchtop height, and run two circuits. I'll put a pair of outlets in
> each box, 1 on each circuit. Can I safely run 12/3 for a pair of 20 amp
> circuits using a common neutral (white) and ground? I'd run the red wire
> (marked black) to one outlet and the black to the other. The two outlets
> would share the white wire, along with the grounds.
>
> At the panel, I'd have the red (marked black) wire going to one CB and the
> black one to a separate CB. If I can do this, I'd have to string way less
> NM... Would this be a violation of code? Is this safe?
>
> I know, I know... call an electrician or an EE... I'm just trying to get
a
> little help here....
What you are looking at is a "split circuit" receptacle. It's been perfectly
legal in a number of locale's, but I am not sure what the latest NEC says
about it.
Two caveats that are generally required to do it:
1. You must cut or remove the metal bridge on the duplex receptacles
2. It is generally required that you must use two, two pole circuit brkr's,
with the two circuit brkr's "tied" together so that if one trips, they both
trip.
In any event, the terminology you want to use with your building inspection
department is "split circuit receptacle".
--
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Last update: 11/06/04
On Fri, 03 Dec 2004 16:56:53 GMT, John Moorhead
<[email protected]> wrote:
> Folks -
>
> I'm back... Now it's a wiring question. I'd like to run a string of outlets
> at benchtop height, and run two circuits. I'll put a pair of outlets in
> each box, 1 on each circuit. Can I safely run 12/3 for a pair of 20 amp
> circuits using a common neutral (white) and ground? I'd run the red wire
> (marked black) to one outlet and the black to the other. The two outlets
> would share the white wire, along with the grounds.
>
> At the panel, I'd have the red (marked black) wire going to one CB and the
> black one to a separate CB. If I can do this, I'd have to string way less
> NM... Would this be a violation of code? Is this safe?
>
> I know, I know... call an electrician or an EE... I'm just trying to get a
> little help here....
>
Are you Canadian? Something similar to that--perhaps exactly--is
standard for kitchens in Canada. I think they may require seperate
jackets, but perhaps not.
I don't think it meets code in the US. At the very least, I've never
seen it recommended for US practice.
Why not just alternate curcuits?
"Doug Miller" <[email protected]> wrote in message
news:[email protected]...
> It is perfectly safe, and does not violate code, as long as:
> a) the two hot conductors are on opposite legs of a 240V service, *and*
> b) a *single* disconnecting means will disconnect *both* of them at once.
> Both of these criteria are easily satisfied by using a standard two-pole
> breaker: the two sides are necessarily on opposite legs, and one handle
> disconnects them both at once.
Doug, you seem to know what you are talking about. What's your experience
with how often this is actually done? It seems to me that, though legal and
safe, someone might forget how this is setup and rearrange breakers/wiring
in the future, creating an unsafe situation. Are there any requirements for
tagging such a configuration?
Bob
"John Moorhead" <[email protected]> wrote in
news:[email protected]:
> Nope - I'm in Northern California... Well, I *do* want alternate
> circuits... The reason for using a single run of 12/3 is that I
> wouldn't have to run an additional separate length of wire -
> everything would be in the one cable. Sorry if my post didn't make
> that clear...
Wire's cheap. Don't skimp.
Patriarch
"John Moorhead" <[email protected]> wrote in
news:%[email protected]:
<snip>
> Believe me... I haven't skimped on ANYTHING with this project - ask my
> wallet!
That's been pretty obvious from the pictures and the enthusiasm.
I think I've spent almost as much on the electrical work as I did on the
Unisaw. I don't worry that it wasn't done right, however.
There are more than enough things that go bump in the night...
Patriarch
Nope - I'm in Northern California... Well, I *do* want alternate
circuits... The reason for using a single run of 12/3 is that I wouldn't
have to run an additional separate length of wire - everything would be in
the one cable. Sorry if my post didn't make that clear...
John
> Are you Canadian? Something similar to that--perhaps exactly--is
> standard for kitchens in Canada. I think they may require seperate
> jackets, but perhaps not.
>
> I don't think it meets code in the US. At the very least, I've never
> seen it recommended for US practice.
>
> Why not just alternate curcuits?
>
"Mike Marlow" wrote in message
> Look at it again Swingman - he doesn't want to split an outlet, he wants
two
> duplexes together in a double box that have their own hots, but share a
> neutral and a ground.
Granted he is using layman's terminology, but are you sure that's what he
meant? ... cuz it damn sure ain't what he said:
>>I'll put a pair of outlets in each box, 1 on each circuit.<<
A single is one outlet, a "pair", or duplex, is two outlets in the same box.
--
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Last update: 11/06/04
"Doug Winterburn" wrote in message
> The answer is "yes". Run 12-3 with ground as you said, but use a ganged
> breaker since if you need to work inside any box, you want both circuits
> shut off. This is exactly what the electrician did for my gar^H^H^Hshop.
> All the left hand duplex outlets in each double box are on one circuit,
> and all the right handers on the other. The 'trician used surface mount
> boxes and conduit with individual wires rather than romex on mine and ran
> a seperate ground even though the conduit can be used for ground. I also
> had him run 2 240V circuits through another single conduit with every
> other box containing a single 240V outlet and alternating between
circuits.
>
> Make sure you have the bottoms of the outlets at least 40" above the floor
> so you can put standard 36" high benches under.
You left out an important step ... on most duplex receptacles you MUST
remove, or cut, the HOT bridge between the two outlets if you are going to
split a circuit.
--
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Last update: 11/06/04
"john" <[email protected]> wrote in message
news:[email protected]...
> It is simply a multiwire circuit. As long as you use a 240v breaker for
> the two circuits, it fine; maybe.
I disagree. You are allowing 40 amps (2 * 20) across a single conductor (the
neutral) by sharing it with two single phase 20 amp circuits.
Bob
On Fri, 03 Dec 2004 23:00:24 GMT, [email protected] (Doug Miller) wrote:
>>Doug, you seem to know what you are talking about. What's your experience
>>with how often this is actually done? It seems to me that, though legal and
>>safe, someone might forget how this is setup and rearrange breakers/wiring
>>in the future, creating an unsafe situation. Are there any requirements for
>>tagging such a configuration?
>
>It seems to me that it's a pretty common thing. There are no requirements for
>tagging it that I'm aware of, but if it's wired properly (double-pole breaker,
>and 12/3 wire, with red and black hot wires) the installation itself should be
>sufficient to identify it as what it is -- and with a double-pole breaker,
>it's impossible to break it up by rearranging the breakers.
Doug is absolutely correct in his posts on this, IME. In fact consider
that if someone wanted a "group" of outlets in one box from two circuits,
12/3 would be the safest way to do it (with all Doug's caveats about the
breakers). (It may be required under the NEC to have all hot wires within
a box controlled by the same breaker, or paired breakers, but I have
unfortunately encountered boxes that are hot from separate breakers.) It
is common in my non-pro experience to use 12/3 to run series of outlets
along a counter, switching circuits back and forth along the way. For
example, in a kitchen. -- Igor
In article <[email protected]>, "Bob" <[email protected]> wrote:
>
>"Doug Miller" <[email protected]> wrote in message
>news:[email protected]...
>
>> It is perfectly safe, and does not violate code, as long as:
>> a) the two hot conductors are on opposite legs of a 240V service, *and*
>> b) a *single* disconnecting means will disconnect *both* of them at once.
>> Both of these criteria are easily satisfied by using a standard two-pole
>> breaker: the two sides are necessarily on opposite legs, and one handle
>> disconnects them both at once.
>
>Doug, you seem to know what you are talking about. What's your experience
>with how often this is actually done? It seems to me that, though legal and
>safe, someone might forget how this is setup and rearrange breakers/wiring
>in the future, creating an unsafe situation. Are there any requirements for
>tagging such a configuration?
It seems to me that it's a pretty common thing. There are no requirements for
tagging it that I'm aware of, but if it's wired properly (double-pole breaker,
and 12/3 wire, with red and black hot wires) the installation itself should be
sufficient to identify it as what it is -- and with a double-pole breaker,
it's impossible to break it up by rearranging the breakers.
--
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Doug Miller (alphageek-at-milmac-dot-com)
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In article <[email protected]>, "Bob" <[email protected]> wrote:
>
>"John Moorhead" <[email protected]> wrote in message
>news:[email protected]...
>> Folks -
>> I'm back... Now it's a wiring question. I'd like to run a string of
>outlets
>> at benchtop height, and run two circuits. I'll put a pair of outlets in
>> each box, 1 on each circuit. Can I safely run 12/3 for a pair of 20 amp
>> circuits using a common neutral (white) and ground?
>
>No.
Yes.
>
>The neutral is a current carrying wire in a single phase circuit. You
>should run 12/3 for each circuit.
I'm sure you meant 12/2 here.
--
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"John Moorhead" <[email protected]> wrote in message
news:[email protected]...
> Folks -
>
> I'm back... Now it's a wiring question. I'd like to run a string of
> outlets at benchtop height, and run two circuits. I'll put a pair of
> outlets in each box, 1 on each circuit. Can I safely run 12/3 for a pair
> of 20 amp circuits using a common neutral (white) and ground? I'd run the
> red wire (marked black) to one outlet and the black to the other. The two
> outlets would share the white wire, along with the grounds.
>
I do not believe this is allowed by the NEC. If you think about it, each of
the two hots will be on 20 amp breakers and will be current limited to 20
amps. The neutral will have to carry the sum of the two circuits, or
potentially 40 amps back to the panel. 12 AWG wire is not rated for 40
amps! You may be allowed to do this if you derate the circuit, but I doubt
you will want to do this.
Frank
In article <[email protected]>, "Bob" <[email protected]> wrote:
>
>"john" <[email protected]> wrote in message
>news:[email protected]...
>> It is simply a multiwire circuit. As long as you use a 240v breaker for
>> the two circuits, it fine; maybe.
>
>I disagree. You are allowing 40 amps (2 * 20) across a single conductor (the
>neutral) by sharing it with two single phase 20 amp circuits.
Nope, not if the two hot conductors are on opposite legs of the 240V service
(which is the only way to meet code). In that case, the current in the neutral
is the *difference* of the two hot currents, not the sum.
--
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Doug Miller (alphageek-at-milmac-dot-com)
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In article <xA1sd.42$IB6.28@trndny06>,
U-CDK_CHARLES\\Charles <[email protected]> wrote:
>On Fri, 03 Dec 2004 17:35:51 GMT, John Moorhead
><[email protected]> wrote:
>> Nope - I'm in Northern California... Well, I *do* want alternate
>> circuits... The reason for using a single run of 12/3 is that I wouldn't
>> have to run an additional separate length of wire - everything would be in
>> the one cable. Sorry if my post didn't make that clear...
>>
>> John
>
>I'm reasonably certain that's not allowed in the US.
This wiring method, the so-called "Edison circuit', *is* allowed in at
least some parts of the U.S. No problem with it, anywhere in the greater
metro Chicago area, for example. I recently re-wired my kitchen, in this
-precise- manner, and the city electrical inspector had no problem with
it. He actually wondered 'why so *many* _neutral_ wires?' -- 'cuz I had
outlets on opposite sides of the breaker panel on the _same_ breaker. The
two hot leads were spliced together in a junction box just before the panel
(no splices allowed _in_ the breaker box), but both neutrals ran straight
through to the bar in the breaker box. Simpler than running wire to the
left-side outlet, and then _back_, and over to the right-side outlet.
'Unconventional', but sound engineering, _and_ code-compliant. <grin>
>In any case, the lone neutral lacks the capacity for both circuits.
Bzzzzt!
As long as the two hot legs are on opposite phases of the 240V feed,
the neutral carries only the _difference_ in the two loads. 'Best
case' is that there is -zero- current in the neutral; 'worst case' is
that there is current in the neutral that is the same as -one- of the
hot legs (where the other hot is supporting -zero- load at that time)
>Also if it's in a garage, the GFCI will sense the imbalanced current and
>trip.
If you use GFCI _outlets_, then there is *no* problem. Speaking from
direct experience here.
To use 'downstream' outlets from a GFCI outlet, you *do* have to have
a 'unique' hot, _and_ a 'unique' neutral, from the GFCI device to the
downstream outlets. You cannot share _that_ wiring across GFCIs.
I'm *not* sure about GFCI _breakers_, having never actually _used_ those
devices. I would _suspect_, however, that they work in the same
manner -- that you can't 'share' the neutral downstream of a GFCI breaker.
"Read the directions" is indicated. <grin>
In article <xA1sd.42$IB6.28@trndny06>, [email protected] wrote:
>On Fri, 03 Dec 2004 17:35:51 GMT, John Moorhead
><[email protected]> wrote:
>> Nope - I'm in Northern California... Well, I *do* want alternate
>> circuits... The reason for using a single run of 12/3 is that I wouldn't
>> have to run an additional separate length of wire - everything would be in
>> the one cable. Sorry if my post didn't make that clear...
>>
>> John
>
>I'm reasonably certain that's not allowed in the US.
And I'm absolutely certain that you're wrong.
This is specifically permitted by the NEC, provided that:
a) the two hot conductors are on opposite legs of a 240V service, and
b) both hot conductors can be disconnected by *one* disconnect.
This is easily implemented with a standard two-pole breaker.
>
>In any case, the lone neutral lacks the capacity for both circuits.
If it is installed in compliance with the NEC (see above), the current in the
neutral is the _difference_ of the currents in the two hots, not the sum.
>Also if it's in a garage, the GFCI will sense the imbalanced current and
>trip.
Well, you did get that part right.
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"Doug Miller" wrote in message
> Not if he's using two duplex receptacles in each box, as it appears he
> intends. And even if he's using one duplex receptacle per box, with each
half
> on a different phase, he still needs to remove the bridge *only* on the
hot
> side.
If you had looked, you would have seen that an immediate post clearly
indicated I had inadvertently left out the word "hot".
> >In any event, the terminology you want to use with your building
inspection
> >department is "split circuit receptacle".
> Not necessarily. That's one duplex receptacle, with each half on a
different
> leg. It sounded to me like he intended each box to have two duplex
> receptacles, with each duplex on a different leg.
I seem to be in the minority, but I am still not certain as to whether that
is exactly what he meant?
Nonetheless, around here it is still referred to as a "split circuit"
whether it be in a duplex or fourplex box, or a series of same.
--
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Last update: 11/06/04
"Swingman" wrote in message
> 1. You must cut or remove the metal bridge on the duplex receptacles
Sorry, I left out the word "hot": That should read "cut or remove the metal
bridge on the HOT side".
The neutral wire metal bridge in the receptable remains intact.
--
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Last update: 11/06/04
In article <[email protected]>, "Frank Ketchum" <[email protected]> wrote:
>
>"Mike Marlow" <[email protected]> wrote in message
>news:[email protected]...
>>
>>
>> I don't see how this would happen. The potential between neutral and
>> ground
>> are the same as if you had run a separate neutral.
>>
>
>A GFCI works by detecting a difference in the amount of current flowing
>though the hot conductor and the neutral. I think this is what he is
>referring to. The neutral will carry the sum of the two branch circuits.
In a *properly* wired circuit of this type, the neutral carries the
*difference* of the individual hot currents.
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"Swingman" <[email protected]> wrote in message
news:[email protected]...
>
> Granted he is using layman's terminology, but are you sure that's what he
> meant? ... cuz it damn sure ain't what he said:
>
> >>I'll put a pair of outlets in each box, 1 on each circuit.<<
>
> A single is one outlet, a "pair", or duplex, is two outlets in the same
box.
>
I think you're reading into what he wrote. Maybe it's just the way I see
it, but I interpreted what he wrote to mean two of something. Not as in a
standard duplex, but as in two separate devices - whether they are single
outlet or duplex.
--
-Mike-
[email protected]
"John Moorhead" <[email protected]> writes:
>Nope - I'm in Northern California... Well, I *do* want alternate
>circuits... The reason for using a single run of 12/3 is that I wouldn't
>have to run an additional separate length of wire - everything would be in
>the one cable. Sorry if my post didn't make that clear...
What you want to do is legal and safe only so long as each of
the two circuits are a different phase (i.e. a different leg of
the 220v). It is also considered wise to handle-tie both
breakers (or use a 220v breaker) so that you cannot have a
situation where one conductor is live and the other isnt.
If the current carrying conductors are on different phases the current
in the grounded conductor approaches zero. If they are on the same
phase, the current in the grounded conductor will be the sum of the
current in each of the current carrying conductors. This would be
considered bad (e.g. 40 Amperes through a AWG 12 conductor).
scott
On Fri, 03 Dec 2004 16:56:53 +0000, John Moorhead wrote:
> Folks -
>
> I'm back... Now it's a wiring question. I'd like to run a string of
> outlets at benchtop height, and run two circuits. I'll put a pair of
> outlets in each box, 1 on each circuit. Can I safely run 12/3 for a pair
> of 20 amp circuits using a common neutral (white) and ground? I'd run the
> red wire (marked black) to one outlet and the black to the other. The two
> outlets would share the white wire, along with the grounds.
>
> At the panel, I'd have the red (marked black) wire going to one CB and the
> black one to a separate CB. If I can do this, I'd have to string way less
> NM... Would this be a violation of code? Is this safe?
>
> I know, I know... call an electrician or an EE... I'm just trying to get
> a little help here....
The answer is "yes". Run 12-3 with ground as you said, but use a ganged
breaker since if you need to work inside any box, you want both circuits
shut off. This is exactly what the electrician did for my gar^H^H^Hshop.
All the left hand duplex outlets in each double box are on one circuit,
and all the right handers on the other. The 'trician used surface mount
boxes and conduit with individual wires rather than romex on mine and ran
a seperate ground even though the conduit can be used for ground. I also
had him run 2 240V circuits through another single conduit with every
other box containing a single 240V outlet and alternating between circuits.
Make sure you have the bottoms of the outlets at least 40" above the floor
so you can put standard 36" high benches under.
-Doug
On Fri, 03 Dec 2004 11:53:33 -0700, Doug Winterburn wrote:
> The answer is "yes". Run 12-3 with ground as you said, but use a ganged
> breaker since if you need to work inside any box, you want both circuits
> shut off. This is exactly what the electrician did for my gar^H^H^Hshop.
> All the left hand duplex outlets in each double box are on one circuit,
> and all the right handers on the other. The 'trician used surface mount
> boxes and conduit with individual wires rather than romex on mine and ran
> a seperate ground even though the conduit can be used for ground. I also
> had him run 2 240V circuits through another single conduit with every
> other box containing a single 240V outlet and alternating between
> circuits.
Also, make sure the ganged breaker is mounted like a 240V breaker with
each half on a different phase so your neutral will never carry more than
the load for the biggest drawing circuit.
-Doug
On Fri, 03 Dec 2004 18:53:58 +0000, Bob wrote:
>
> "john" <[email protected]> wrote in message
> news:[email protected]...
>> It is simply a multiwire circuit. As long as you use a 240v breaker for
>> the two circuits, it fine; maybe.
>
> I disagree. You are allowing 40 amps (2 * 20) across a single conductor
> (the neutral) by sharing it with two single phase 20 amp circuits.
I disagree. As long as each breaker is on the opposite hot as in any
240V circuit, the total neutral load will never exceed the current draw of
the largest circuit load. If each circuit was drawing an equal load, the
neutral load would be zero.
-Doug
"John Moorhead" <[email protected]> wrote in message
news:[email protected]...
> Folks -
> I'm back... Now it's a wiring question. I'd like to run a string of
outlets
> at benchtop height, and run two circuits. I'll put a pair of outlets in
> each box, 1 on each circuit. Can I safely run 12/3 for a pair of 20 amp
> circuits using a common neutral (white) and ground?
No.
The neutral is a current carrying wire in a single phase circuit. You
should run 12/3 for each circuit. I think you may be trying to be too
symmetrical and neat by putting two branch circuits in the same box. It
also crowds the box and makes connections more difficult. But I'm assuming
that you are placing outlets at some reasonable spacing for a shop (Lots of
'em).
Its only an opinion, but my philosophy is to use multiple outlets for
connectivity, as opposed to load carrying capability. My shop has three
heavily interactive walls (bench and portable tool areas). I put one branch
ciruit in each area and populated it with an embarrassingly high number of
outlets. I also ran one 220 ciruit to each area with 3 outlets each.
Bob
On Fri, 03 Dec 2004 18:56:12 +0000, [email protected] (Robert
Bonomi) wrote:
>You do -not- need to 'tag' the red wire as black, btw. anything _other_
>_than_ one of the 'reserved' colors (white, green, bare) is presumed to
>be a 'hot' lead.
I think that is correct. OTOH, sometimes one must tag a white wire as
black (hot), such as in a 2-wire (plus ground) 240 circuit or in some 3-way
switch configs. -- Igor
"Mike Marlow" <[email protected]> wrote in message
news:[email protected]...
>
> "Swingman" <[email protected]> wrote in message
> news:[email protected]...
> >
> > Granted he is using layman's terminology, but are you sure that's what
he
> > meant? ... cuz it damn sure ain't what he said:
> >
> > >>I'll put a pair of outlets in each box, 1 on each circuit.<<
> >
> > A single is one outlet, a "pair", or duplex, is two outlets in the same
> box.
> >
>
> I think you're reading into what he wrote. Maybe it's just the way I see
> it, but I interpreted what he wrote to mean two of something. Not as in a
> standard duplex, but as in two separate devices - whether they are single
> outlet or duplex.
I will agree that you can take it either way, Mike.
However, it makes no difference... what I said in my original post will
still work as a "split circuit" whether the box is a duplex, fourplex,
separate boxes four feet apart, or even a single outlet at the end of the
run.
--
www.e-woodshop.net
Last update: 11/06/04
"Doug Miller" <[email protected]> wrote in message
news:[email protected]...
> In article <[email protected]>, "Bob"
<[email protected]> wrote:
> >
> >"John Moorhead" <[email protected]> wrote in message
> >news:[email protected]...
> >> Folks -
> >> I'm back... Now it's a wiring question. I'd like to run a string of
> >outlets
> >> at benchtop height, and run two circuits. I'll put a pair of outlets
in
> >> each box, 1 on each circuit. Can I safely run 12/3 for a pair of 20
amp
> >> circuits using a common neutral (white) and ground?
> >
> >No.
>
> Yes.
> >
> >The neutral is a current carrying wire in a single phase circuit. You
> >should run 12/3 for each circuit.
>
> I'm sure you meant 12/2 here.
Yes, I stand corrected.
Bob
In article <[email protected]>, "Bob" <[email protected]> wrote:
>
>You are correct. My statement only applies if both branches come off the
>same leg.
Which is, of course, exactly the reason that code prohibits doing that way.
--
Regards,
Doug Miller (alphageek-at-milmac-dot-com)
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In article <[email protected]>, "Mike Marlow" <[email protected]> wrote:
>
>"U-CDK_CHARLES\Charles" <"Charles Krug"@aol.com> wrote in message
>news:xA1sd.42$IB6.28@trndny06...
>> Also if it's in a garage, the GFCI will sense the imbalanced current and
>> trip.
>
>I don't see how this would happen. The potential between neutral and ground
>are the same as if you had run a separate neutral.
>
GFCIs operate by sensing the currents on the hot and neutral. If they differ
by more than 20ma, the GFCI opens -- the point being that if the currents are
not the same, then there must be leakage somewhere.
Consider this:
red -----------------********
* *
white -----------------* GFCI *------------***************
(neutral) * * * insert 120V *
******** * load of your*
* choice here *
black -------------------------------------***************
As soon as a load of more than 20ma is applied between the black and the
white, the GFCI will trip, because the current in the white wire does not
balance the current in the red wire.
--
Regards,
Doug Miller (alphageek-at-milmac-dot-com)
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On Fri, 03 Dec 2004 17:35:51 GMT, John Moorhead
<[email protected]> wrote:
> Nope - I'm in Northern California... Well, I *do* want alternate
> circuits... The reason for using a single run of 12/3 is that I wouldn't
> have to run an additional separate length of wire - everything would be in
> the one cable. Sorry if my post didn't make that clear...
>
> John
I'm reasonably certain that's not allowed in the US.
In any case, the lone neutral lacks the capacity for both circuits.
Also if it's in a garage, the GFCI will sense the imbalanced current and
trip.
In article <[email protected]>, igor <[email protected]> wrote:
>
>Doug is absolutely correct in his posts on this, IME. In fact consider
>that if someone wanted a "group" of outlets in one box from two circuits,
>12/3 would be the safest way to do it (with all Doug's caveats about the
>breakers). (It may be required under the NEC to have all hot wires within
>a box controlled by the same breaker, or paired breakers, but I have
>unfortunately encountered boxes that are hot from separate breakers.) It
>is common in my non-pro experience to use 12/3 to run series of outlets
>along a counter, switching circuits back and forth along the way. For
>example, in a kitchen. -- Igor
The NEC requires that all ungrounded conductors be capable of being
disconnected simultaneously by a single disconnecting means. A single,
two-pole breaker is by far the easiest way of achieving this, but it isn't the
only method that complies with that requirement. E.g. two widely separated
single-pole breakers, connected with a rigid handle tie, would satisfy.
--
Regards,
Doug Miller (alphageek-at-milmac-dot-com)
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"John Moorhead" wrote in message
> Hello there -
>
> Well, a wealth of posts to the point of confusion as to who's saying
what...
> anyway, I *am* a layman, and apparently don't have the nomenclature
korrect,
> I want a total of 4 plug-thingies in a double box, thus two pair... the
left
> on 1 circuit and the right on the 2nd circuit... But, for now, I have
> decided to just run 12/2 and say the hell with it...
LOL ... I stand corrected.
--
www.e-woodshop.net
Last update: 11/06/04
Hello there -
Well, a wealth of posts to the point of confusion as to who's saying what...
anyway, I *am* a layman, and apparently don't have the nomenclature korrect,
I want a total of 4 plug-thingies in a double box, thus two pair... the left
on 1 circuit and the right on the 2nd circuit... But, for now, I have
decided to just run 12/2 and say the hell with it...
John Moorhead
"Swingman" <[email protected]> wrote in message
news:[email protected]...
> "Mike Marlow" wrote in message
>
>> Look at it again Swingman - he doesn't want to split an outlet, he wants
> two
>> duplexes together in a double box that have their own hots, but share a
>> neutral and a ground.
>
> Granted he is using layman's terminology, but are you sure that's what he
> meant? ... cuz it damn sure ain't what he said:
>
>>>I'll put a pair of outlets in each box, 1 on each circuit.<<
>
> A single is one outlet, a "pair", or duplex, is two outlets in the same
> box.
>
> --
> www.e-woodshop.net
> Last update: 11/06/04
>
>
>