Three way switches with 12/2 wire?

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My older house is wired differently than any of the books or online schematics I've seen and need some help and feedback. They have wired two three-way switches and an outlet using only 12/2 wire. How you ask?
Hopefully this can explain: Switch 1 Common<->black of incoming power Traveler1<->black of outgoing 12/2 wire Traveler2<->white of outgoing 12/2 wire Switch 2 Traveler1<->white of incoming 12/2 wire from Switch 1 Traveler2<->black of incoming 12/2 wire from Switch 1 Common<->black of outgoing 12/2 wire to outlet Additional wiring in Switch 2 box White of incoming 12/2 wire (second power source)<->White of outgoing 12/2 wire to outlet Black of incoming 12/2 wire (second power source)<->two-way switch on an unrelated light
Outlet Typical hot/neutral 12/2 wiring
What I want to do is add a light that is also three-way switched using these switches. I want to keep the outlet as is and wire the light between Switch 1 and Switch 2. The outlet is not accessible to pulling additional wires.
Please help if you understand this interesting wiring scenario. Thanks.
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snipped-for-privacy@gmail.com wrote:

I understand enough to know the kind of language someone working on them 10 years from now is likely to use, it they can speak at all.
--
Joseph Meehan

Dia duit
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Ideally you could come off of one of the light locations and run a new cable to the location of the light. Or you could add a cable from switch 2 to the new light location. Is your box big enough to add another cable. into it?
By the way in residential the only thing that is odd is that they used 12.
Any other solution is not as "clean"
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You are in for some trouble, since your existing wiring is completely against code, and a bad situation to boot.
Just think for a second about how this circuit looks. The current's path starts at a circuit breaker (on a black wire) goes to a switch 1, goes to switch 2, goes to the outlet, goes into the appliance, (and now on the white wire) back out of the appliance, back to the outlet, back to switch 2, but now takes a turn and heads down a different path to possibly a handful of other boxes and junctions, who knows where else, then eventually back to the neutral in the breaker panel.
Essentially you have a big 1-wind electro-magnet here. Besides breaking code, I can think of dozens of consequences, e.g.:
You are broadcasting emf interference all over the place, probably interfering with radios, televisions, and other wireless devices. (And I have heard stories of such circuits interfering with hearing aids and all sorts of other sensitive electronics and things with antennaes, even over to your neighbors houses).
You can get inductive heating in several of those junction boxes, posing a fire hazard.
Heaven forbid someone reverse the hot/neutral in some other place in your house that happens to share one of those power sources. You would either get two same hots at your outlet, or 240V. You don't even mention if the two power sources are on the same circuit breaker or not.
If someone puts a GFCI somewhere on one of those two now-joined circuites, it would either trip constantly (b/c of too little current on the neutral in the one case), or it would not protect you in the way it is supposed to (b/c of too much current on the neutral).
In other words, besides the potential for future changes to make this much worse than it already is (and who knows, maybe it already is much worse -- you don't know unless you have traced through the WHOLE circuit on both sides, everywhere it goes), you have some active problems like inductive heating and radio interference.
Lucky for you, this is pretty easy to fix. Just ditch the one power source, and add a 12-3 cable where it belongs.
-Kevin
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Ok Kevin get out your code book and post the back up to your statement, give sections and page numbers.
I have never found a color code in the NEC, especially when it is residential. ( ok there is one reference to a color code but it does not apply to this situation)
I await your code sections.
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Article 300-3 (b) might:
Conductors of the same circuit. All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductords shall be contained within the same raceway, auxillary gutter, cable tray, trench, cable, or cord....

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You left out "unless otherwise permitted in accordance with (1) through (4)". One of those exceptions is for non-metallic cable. Since the OP says "12/2" it sounds like the exception would apply in this case. The exception does reference another section requiring such cables to use the same opening in metallic boxes.
Doug
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You are correct-I didn't read 300-3-b-3....
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Rick wrote:

IMHO. Inconcievable the code would permit wiring from 2 divergent paths as in the situation described. It used to be a California 3-way, which requires 4 wires, could be wired with 2 2-wire Romexes run together. It can't anymore because of changes to 300.3B unless you can find 4 wire Romex.
While a light bulb in the open loop as described by Kevin is unlikely to produce interference problems, a high current could. It does not take much 60Hz magnetic field to affect a computer monitor. One of the reasons to run circuit wires together is magnetic field cancellation.
bud--
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Bud-- wrote:

I'm pretty sure an AHJ would allow it either, but the wording is vague (I don't have the actual text with me at the moment).
There are a few other issues, too, but all agree it's not good practice....
A true California 3 way would put the bulb between two neutrals or hots, too.
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Were there changes since the 2002 code regarding this? If not, then 300.20B covers metal raceways OR metal enclosures in scenarios such as this. The metal enclosures part is what applies here.
I'm not an electrician but I did rewire my house with an inspection including a circuit with an imbalance like this in the past year. The 2002 code applied. The circuit involves 3 location switch control of half of 2 receptacles with the other half of the receptacles always hot. The room has 3 entrances. A book I have that interprets the code (Electrical Wiring Residential by Ray C. Mullin) has several pages devoted to this topic. My understanding is that this is a well respected textbook for electricians. The author's interpretation is that the code is concerned with induction heating and that is avoided by using all non-metallic wiring and boxes or non-metallic wiring and passing divergent conductors through the same entry point in a metallic box.
4 wire romex is out there but hard to come by and overpriced for what it is. I couldn't get a reasonable quantity for my purpose.
Doug
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kevin wrote:

Really? At 60 Hz? I hardly think so. Way too low in frequency to cause any radio or televison interference. The degaussing coils in TV sets put out a hell of a lot stronger magnetic fields than 10 or 15 amperes flowing in a single turn loop will, and I've never heard tell that they bothered any adjacent devices.
Maybe, just maybe, a hearing aid held a couple of inches away from a monoconductor carring a few amps of 60 HZ might pick up a litle hum, but that's about it Kevin.
If you furnish some valid cites I'll be pleased to learn something new and back down.
Jeff
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Jeffry Wisnia

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You may be right. My "probably interfering with radios, ..." was perhaps too strong. I think that my point stands however. This kind of multi-path circuit is specifically forbidden, and is a bad idea for many reasons, including the reasons I cite: emf, inductive heating, potential for mistakes down the road including messing up GFCIs. Another one that I did not think of, but noticed upon searching, is the potential for increased impedence of the circuit (related to the inductive heating, I beleive), and impedence of the ground path (depending on how the grounds were run).
I don't claim expertise in this area, but there seems to be fairly strong agreement out there that the wiring described is bad. Here are some relevant citations, easily found via Google (I can't back these cites up, you will have to evaluate them yourself).
http://www.mikeholt.com/technical.php?id=grounding/unformatted/emf&type=u&title=Electro%20Magnetic%20Fields%20 (EMF) (Description of emf problems that can be caused by described wiring)
http://www.mikeholt.com/mojonewsarchive/NEC-HTML/HTML/Article-300-Wiring-Methods~20031029.htm (Same site, describing the 300 section of the code which forbids this wiring -- and no, SQLit, it has nothing to do with "color", it has to do with conductors of the same circuit passing through different raceways, different metallic conduits, different metal holes in boxes, etc., which are all extremely likely given the wide physical separation of the hot and neutral circuits as described).
http://www.dhs.ca.gov/ps/deodc/ehib/emf/WiringProtocol.pdf (A fairly convincing report on the generation of emf from poor wiring identical and similar to that described by OP, with code citations for you SQLit, along with description of other effects of this poor wiring including inductive heating.)
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kevin wrote:

I agree with you on everything else you said, and you may have noted I was in the ranks of those who told the OP to straighten out and do it right.
The worst example of this sort of thing I've personally experienced was when some clod who was too lazy or cheap to go out and get a piece of the correct size conduit used what he had and ran three three lengths of 1/2" conduit about 30 feet long between a breaker panel and a disconnect switch and then put the three conductors for a 75 amp three phase circuit through them, one conductor in each.
He called me in to explain why he was getting arcs and sparks where the conduit fittings attached to the panel housing and the switch box every time he tried to start the machine it powered.
<snipped>
Jeff
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[snip]

Just so I know, too, why was he gettint arcs and sparks?
--
charles

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On Sat, 21 Jan 2006 03:12:36 GMT, snipped-for-privacy@earthlink.netttt (Charles Bishop) wrote:

Maybe the panel housing is grounded, the conduit wasn't installed right (loose fittings), and there's a short in the switch box.
--
Mark Lloyd
http://notstupid.laughingsquid.com
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Charles Bishop wrote:

Because of voltages induced in the conduit, which is why the code is specific about all conductors of a circuit having to be in ONE conduit or raceway.
Each of the three conductors acted like the primary winding of a transformer, and each piece of conduit acted like a secondary winding.
The ends of the conduits were connected together by the boxes, and some of the mechanical connections there weren't tightened as well as they shold have been. So sparks and a bit of smoke happened at those joints because of the current flowing in them from those shorted out "transformer secondaries" when 75 amps of current flowed through the "primaries".
Even if those mechanical joints had beed socked down so they had low resistance, the conduits would probably have gotten pretty hot just from induced current flowing through them.
If all conductors were in ONE conduit, the magnetic fields from the three wires would have canceled out nearly completely, leaving a negligible remaining field to induce a voltage in the conduit.
Same principle applies for two conductors in a single phase circuit.
Jeff
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Jeffry Wisnia

(W1BSV + Brass Rat \'57 EE)
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snipped-for-privacy@conversent.net says...

When the guy in the next office comes to work in the degausing coil in his monitor makes my monitors go all jumpy. There is a hell of a magnetic field there, but only for a second or so. ;-)

--
Keith

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ok guys, help me out here............
I learned my electrical skills working with industrial / commericial electricians on a couple of long term residential upgrades / rewires, by reading the NEC & various texts that interpret the NEC in to real English.
I was under the impression (& have always done work this way) that green & white were "restricted colors";
white only for solid neutral & green for ground; all other colors ok for hots & swiitch legs
I have seen lots of installations (only in residential) where 12/2 NM with ground was used for bathroom & bedroom switch legs;
that is where the white conductor in the NM cable was attach to one of the switch poles & it was also wired nutted to a hot (black) in the ceiling box!
Very confusing & a pain in the ass to reowrk when someone discconects all the connections & fails to label them & says "I can't get it to work now"
So what is the deal with colors, esp white & green?
cheers Bob
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snipped-for-privacy@gmail.com says...

Whoa! I'm just an engineer! ;-)

I think green (or green with yellow chaser) is. Not sure about white.

12/2NM should have black, white, and bare conductors. The switched leg should be black.

Ugly, but I think it's legal. The "white" should have a hunk of tape on it or "painted" black with a marker.

It can also lead to "I can't get him to breathe now".

You won't see too much green anymore in home wiring. Grounds are usually bare. White *should* be reserved for the "grounded conductor" (neutral). Black or red *should* be used for the hots or switched hots. ...but I don't do wiring for a living. When I do it, I make sure it's more than right.
--
Keith

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