Question on 300.3b and 3ways

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big john said:
I can't say I like it very much, but if it's legal, it may potentially be a lot cheaper than re-pulling the travelers.
-John
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John it is legal if the wiring method is a nonferrous type-- as nm cable. I don't like it either but......
 
georgestolz said:
Here is a picture of a two-wire threeway, which I call a California Threeway. A neutral is stolen from elsewhere in the circuit, if power exists in both boxes already.
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What you have there is a "bastard neutral". (Can I say that?)

The "California 3-way" (AKA "Hollywood" as the whole state is trying to dismiss claiming as their own.*) that I know and loath is slightly different than what I can gather from the link you have there. And there is no easy method of a 4-way situation with it. In fact beyond being illegal, nothing easy about it. See attached:

* of it's many names "Chicago" etc. I think it's more a passing of blame than taking credit in this case in regards to what it is called regionally. There are many other derogatory names for it as well....

And both are perfect examples of violating the code in question here....
 
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I'm sorry .... I don't understand your schematic ..... And it's very easy to pull a 4 way with 2 wire travelers with power at both sides on the same circuit.
 
Okay You have a hall ...one circuit power at both ends. You take the switch leg from one of switches on one end and run a 12/2 between for the 3ways and or maybe a 4 way in between. 2 Wires for travelers and a ground.... How does that cause Elevated MF fields. If you put a working neutral in the mix such as 3 wire, the argument is that MF fields go down.

Another circuit
Now run a 3 wire for 2 3ways, no power at one side and no switchleg at the there either. I send my power on my red.. Same difference. Still no neutral.

What if you have 3 3ways going to the same box on the same circuit ..... 2 wire or 3 wire guess what ..... Different cables....

OK now everyone here knows that we have wire everywhere and running alonside each other for some distance and some pretty far apart on the same circuit. I really dont think that a 3 way run with a just travlers and a ground is going to cause any signifcant EF levels .......

I just don't follow that thinking....
 
magnetic fields

magnetic fields

Because magnetic fields cancel each other when run in opposite directions take for example a 120 watt (I made this part up) lightbulb on a 120 volt sinle pole switch. From the switch you will have 1 ampere running out on the hot and back on the neutral. Using the right hand rule of magnetic fields current being in the direction of your thumb. The fields have both an equal and opposite direction effectively canceling each other. when you split up the current path the magnetic fields cannot cancel . This is a real situation.(except for the 120 watt light bulb I made that up)
 
quogueelectric said:
Because magnetic fields cancel each other when run in opposite directions take for example a 120 watt (I made this part up) lightbulb on a 120 volt sinle pole switch. From the switch you will have 1 ampere running out on the hot and back on the neutral. Using the right hand rule of magnetic fields current being in the direction of your thumb. The fields have both an equal and opposite direction effectively canceling each other. when you split up the current path the magnetic fields cannot cancel . This is a real situation.(except for the 120 watt light bulb I made that up)
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Understood ..... is that to say that drop switching is also in question?
 
talightning said:
I'm sorry .... I don't understand your schematic ..... And it's very easy to pull a 4 way with 2 wire travelers with power at both sides on the same circuit.
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Which schematic? The one I posted 'CA3way', or the one Dennis posted?

The one I posted would still be a violation of 200.10D, and 410.47. (A few places in between as well?) The difficulty is in correcting that... Or you could chaange the fixture to a bayonet style??? And you would still never be able to put a dimmer on it without say, Radio RA or equal. (+Making a perminant neutral to the fixture.)
 
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e57 said:
Which schematic? The one I posted 'CA3way', or the one Dennis posted?

The one I posted would still be a violation of 200.10D, and 410.47. (A few places in between as well?) The difficulty is in correcting that... Or you could chaange the fixture to a bayonet style??? And you would still never be able to put a dimmer on it without say, Radio RA or equal. (+Making a perminant neutral to the fixture.)
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Sorry ... It was the one you posted. That was not my situation.
 
talightning said:
Sorry ... It was the one you posted. That was not my situation.
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Sorry what was your situation? Oh yes, it was the perfectly legal one - except if in EMT, AC or MC. Sorry I was thread-jacking a little.
 
OK, I'm confused.....

OK, I'm confused.....

Just for clarification, here are 2 diagrams of weird three-way switching. I was just wondering which one applies to this discussion? By the way, I found the sketch online. I'm not sure either one of these methods would be legal according to the NEC.

rare3ways.gif
 
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supergeek said:
Just for clarification, here are 2 diagrams of weird three-way switching. I was just wondering which one applies to this discussion?
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Your second diagram is what e57 drew, and is illegal.

However the system that started the discussion is a 'normal' 3-way arrangement, with the 'hot' switched between one of two travelers...but with the neutral not carried with the travelers.

The real issue being discussed is the separation of current carrying conductors, which the NEC prohibits in many but not all cases.

A slightly different way of thinking about the 'emf' issues caused by separated conductors is to consider the 'loop area' between the conductors. In this loop the current in the conductors will create a magnetic field. The larger the loop, the larger the area influenced by this magnetic field, the greater the inductance of the circuit, and the greater the inductive voltage drop. Add a ferromagnetic raceway, and this inductance is increased further. When all of the conductors of the same circuit are next to each other in the same cable or raceway, the loop area (and thus the total EMF) is minimized.

-Jon
 
Supergeek, the diagram you have on the top is the one of the topic. The one on the bottom that you posted is simular to the one I brought up to clarify the the differences in a "California 3-way" metioned in post 10, which is often reffered to as a "Bastard Neutral" - just wanted to clarify it. (As it too does not describe the one discussed in the OP.)

As we can see there are a whole lot of ways to make a light work, and a lot of them are not right.... Not sure what the OP's wiring method is, but if it is NM it is OK. By the code at least, but sounds as if someone showed up with a 20th century divining rod (gauss meter), or maybe just looked at the wiring in the box and pulled out a 'red card' on his "Magnetic Field Survey". (Then he pulled out is cell-phone.... :D )

Either way, there will more and more talk (if allowed) about this and a few other related subjects as more of these types of surveys become more common and possibly required in the immediate future.
 
Wow, now I'm more confused than ever. :D

The top picture of Supergeek's post shows a "Travelling Bus" threeway, with the commons tied together and the switchleg/hots at the traveller terminals. It is likely a violation of 310.4, so it is not "legal" as the picture states.

The OP does not describe a "Bus", he's describing a normal threeway without the neutral being carried along to cancel EMF. It's what I posted in post #10, as mentioned above.

(Sidebar: Mark, I'd call mine a Cali, and yours a Chicago. :D )
 
Sorry George, Might be having trouble seeing it in diagram, if the neutrals were in the same circuit or not? If they are you might be on the right track..... (I think?)

Either way, I think we could have another discussion about what they are called. :D

But in the fist diagram in supergeeks post - the conductors are in series - not parralel - so legal if in NM cable.

And really at some point it might be cool to have a refferance area full of diagrams here in the same format that we can identify - so we are talking apples and apples about these things...
 
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