Question on 300.3b and 3ways

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talightning

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On occasion I have wired a 3 way in the following manner. If I have 2 switch banks on the same circuit (lets say two 2 gang boxes on each end of a hall) I will run a 12/2 between for travelers and use the same neutral on each side for that 3 way circuit. Power at both sides and SL on one of them.
I have an Enviromental Contractor telling me that is against code and he cited 300.3b. Is this true ?... Any help is appreciated
 
talightning said:
I have an Enviromental Contractor telling me that is against code and he cited 300.3b. Is this true ?... Any help is appreciated
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Not true-- if you are using nonmetallic cable. You should be aware that this type of installation creates much discussion and also cause higher EMF's readings than one would want. For that reason many contractors will not wire a 3 way in the manner you suggested.
 
Should add that the nm cable can't be run thru holes in metal, i.e. metal

boxes, or metal studs, or any kind of metal connector. I don't know if this is

the situation or not ??

On a personal note, I don't care for that type of threeway set up.JMO.
 
I ask the question because the term "environmental contractor" here in Florida typically means an Asbestos, Mold, or Water Damage Removal company.

I can't figure out why someone in this line of work is interested in how 3-ways are wired up?
 
How does the circuit work?

How does the circuit work?

I'm a little confused on how your circuit works.

If you bring your feed into box "A" and run a 12/2 to box "B", which box do you run your switch leg for the light from? If your switch leg to the light comes from box "B", where is the neutral coming from? If your switch leg comes from "A" and you have 2 travelers between "A" and "B", how does the switch leg get back to the light?

Do you bring the feed into the light, run a 2 wire to each switch from the light (feed and neutral to one, switch leg and neutral to the other) and a 2 wire between the switches for travelers? If so, this scenario would have a neutral in each switch box connected to nothing.

Can you explain how the circuit is wired a little more?
 
Okay this is what he put on his report.

The NEC code violation is 300.3(b) Conductors of the Same Circuit. "to keep impedance and induction as low was possible...all conductors of the same circuit, including the neutral...shall be contained in the same raceway, cable tray, cable, trench, or cord."

Obviously that is not the wording in the code book.


I have never heard of this violating code. Any one know if it does or doesn't

BTW I agree it's a title to keep his pockets green. He called it a Magnetic Field Survey.
 
He obviously is dealing with Electro-Magnetic Fields. EMF's are not a problem according to the NEC however some organizations claim it can have some bad side affects on individuals who are exposed for long periods of time.

Here is an axample of a 4 way switch that will create EMF's.

4-way-switch.gif

To get rid of the Emf's you would have to run the neutral through each switch box up to the light as in the following picture.

 
talightning said:
Okay this is what he put on his report.

The NEC code violation is 300.3(b) Conductors of the Same Circuit. "to keep impedance and induction as low was possible...all conductors of the same circuit, including the neutral...shall be contained in the same raceway, cable tray, cable, trench, or cord."

Obviously that is not the wording in the code book.
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Have you looked at 300.3(B) in the code book, that is pretty close to the wording.

BUT...300.3(B) goes on and if you look at 300.3(B)(3) it gives permission not to keep them altogether if you use Nonferrous wiring methods.
 
benaround said:
A person who is trying to keep his pockets ' green'.
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Picking myself off the floor... But without getting into the politics of the profession. (Which would offend Bob deeply) I wonder what type of certification or credential allows oneself to call themselves one? As the term is pretty broad in trade scope, and market for it new in the sceme of things.
 
e57 said:
But without getting into the politics of the profession. (Which would offend Bob deeply)
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This is a National Electrical Code Forum.

You have no idea what may or may not offend me, for all you know I may be a strong supporter of the NRA or maybe I am for Green Peace or maybe I believe we should build a wall around the CA boarder and make CA 'Newer Mexico'....but I will not talk about any of that here, it's not the place for that. :D

If you decided to take a Math refresher course would you expect the curriculum to include a foreign language?

It seems straight forward to me. :confused:
 
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iwire said:
You really just don't get it do you? :confused:

This is a National Electrical Code Forum.

You have no idea what may or may not offend me, for all you know I may be a strong supporter of the NRA or maybe I am for Green Peace or maybe I believe we should build a wall around the CA boarder and make CA 'Newer Mexico'....but I will not talk about any of that here, it's not the place for that. :D

If you decided to take a Math refresher course would you expect the curriculum to include a foreign language?

It seems straight forward to me. :confused:
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Sorry Bob, I maybe should have thown a smiley o' two in with that??? And you're right it's a code forum - and I (Although I am one of the many offenders of that policy) want you to know that your enforcement of it, and your strict but equal IMO adherence to it are appreciated - here and elsewhere where you moderate. But you should know - I do try... (As many of us do...) To hold back the flood of political content that could come flying on to every post.

Add: I'm sure many of us could not even begin to tell 'what' we hold back as doing so would be crossing the line.

But sorry if I offended you personally. Also - it seems you are crossing a milestone of 16000 posts here alone, many of which I am sure were in effort to perform your role as moderator so beautifully.
 
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I just want to make sure I understand this correctly:

I've run into it a couple of times now that usually due to some error, a 3-wire was not pulled between two 3-way switches. So, as I read 300.3 it is entirely permissable for me to leave the two-wire NM traveler, and derive the neutral for the light fixture from any accessible point as long as it is on the same circuit as the feed for that light? Much in the same manner as many K & T installations are run?

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
 
e57 said:
But you should know - I do try... (As many of us do...) To hold back the flood of political content that could come flying on to every post.
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Thanks Mark I do appreciate that and the rest if the kind words.

I know you want to say more than you do and I am sure others try as well.

I apologize if I was to sharp, I just got back from a hot, dusty, expensive carnival with the family and may have been a bit on edge. :D
 
Back on topic: 300.3(B)(1) through (4) are fairly clear as to when and when you can deviate. #4 is the only vague item - which describes a practice of placing a neutral bar in a connected cabinet to a panel. (Still the full sized neutral would be run in this box/gutter with the branch conductors. Just not required in the panel.)
 
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