3 way switches

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Re: 3 way switches

RBJ,

In other words, 300.3(B)(3) says one can run single conductor cables and one can install a single conductor in, say, PVC raceway. The return conductor can be routed elsewhere, if the wiring method is nonferrous.
 
Re: 3 way switches

Rbj, I agree with Al.

I would also point out Jap's kicker, "Where Used". If a grounded conductor (or any other conductor of a cicuit) is not used in a part of the physical circuitry, it is not required to be in the cable or raceway if it's absence does not relate to inductive heating of the raceway or enclosure.

Even if a grounded conductor (or any conductor of the circuit) were run with a set of two travelers and not connected to any thing, it would not cancel current or an EMF.

With the exception of this one section of the code, most EMF problems are negated with a code compliant installation.

Roger

[ November 03, 2004, 06:24 PM: Message edited by: roger ]
 
Re: 3 way switches

al,

I understand where 300.20(B) is on induced heating in steel conduit. I translate induced heat as coming from a source of current being generated from single radiating conductors not being circuit paired.

At some point all the cumulative net-current must go through a main 'ferrous' enclosure that for sure is included in the meaning mentioned in 300.20(B) specifying metal enclosures. Does there exist another way with an easier degree of practicality?
Two conductor travelers are a source of electromagnetic radiation that can be detrimental to electronics and individual health. Am I wrong?

rbj, Seattle
 
Re: 3 way switches

Rbj, most (I said most, not all) residential methods include plastic or fiber boxes.

Two conductor travelers are a source of electromagnetic radiation that can be detrimental to electronics and individual health. Am I wrong?
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I agree, but this unfortunatly is not a direct NEC issue.

Roger

[ November 03, 2004, 09:01 PM: Message edited by: roger ]
 
Re: 3 way switches

BTW, the health issues are still debated, but I lean towards not thinking it is a good thing.

Karl Riley, one of the moderators here, is a respected author and expert in this area.

Roger
 
Re: 3 way switches

Two conductor travelers are a source of electromagnetic radiation that can be detrimental to electronics and individual health.
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On both points I say show me. :)
 
Re: 3 way switches

Originally posted by physis:
Two conductor travelers are a source of electromagnetic radiation that can be detrimental to electronics and individual health.
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On both points I say show me. :)
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Karl Riley would be able to do both.

I will only say it is a fact that EMF can and does cause PC monitors to flicker and this can be more than an annoyance.
 
Re: 3 way switches

Rbj, you can also Click Here for more information on Karl's literature.

Roger

[ November 04, 2004, 06:43 AM: Message edited by: roger ]
 
Re: 3 way switches

Hi Bob, I'm not meaning to argue with you but this is my take

How come nobody ever has a problem with their television set? Only their computer monitors.

I'll concede that there can be a detrimental effect but I'll also point out that the magnetic field isn't free to go any where it wants. I beleive it's energy is reduced to the square of the distance, it doesn't have much effect unless you're near it. I have half a mind to put an amp or two through a single conductor behind my monitor to see what it does. I just put a speaker with a fair size magnet (not a great big one) near my monitor and it had no effect at 5 or 6 inches. I'm not saying we shouldn't bother to be aware of this and reduce or eliminate it where possible, I advocate running the neutral with the travellers, but everthing in the universe isn't so delicate that it barely works either.

As for the medical connection, my beleif is that it's mostly phycosomatic. There are many many people who are running around getting sick from everything. That's not to say I'm unwilling to accept that there may be some reality to it as well. I so far haven't seen anything compelling. I haven't followed all the links your link points to yet. :)

Edit: I had to remove something.

[ November 04, 2004, 12:40 PM: Message edited by: physis ]
 
Re: 3 way switches

Physis,

The physiological effects of EMF is a subject that has a mass of peer reviewed published studies. A good portal to the raw information is at the National Institute of Environmental Health Science. This link is to the EMF Research and Public Information Dissemination Program of the NIEHS.

Each of us is immersed in a complex electromagnetic soup. The consistency and constituents of the "soup" vary depending upon the nature of the transmission sources and signal strengths where one is standing. As a rule of thumb, the higher the population density and the greater the concentration of electrical technologies, the richer the "soup" is.

The published studies demonstrate specific physiological effects, but, in the general sense, cannot yet link the effects causaly to specific long term systemic degenerative processes. Our medical science, while good, is not yet good enough for this linking.

I find it very unsettling that there are so many documented effects.

If I can minimize the stressors on my body (ingested toxins, nicotine, dietary fat, bad air, bad water, etc.) I will lower my potential to succumb to a long term systemic degenerative process. I believe that EMF is another such stressor, and will be proven, eventually, to be so.
 
Re: 3 way switches

I just tuned into this thread, so will add my comments. rbj was replying in the way I would, but other points were raised.

Physis, a circuit generating a net current due to neutral current traveling outside the circuit does not weaken with the square of the distance, it weakens only directly with distance. This is why it is so pervasive. And it is not restricted by shielding materials, so you have to deal with the wiring.

I do trouble shooting re electronic instruments. Standard computer monitors (not LCD) will start flickering between 5 mG and 12 mG. These levels can be generated by 3-way wiring where the installer tries to save money by using 2 conductor travelers.

Knob and tube generates high fields for the same reason.

Health research continues but now it is generally recognized that 4 mG is associated with doubling of childhood leakemia.

The recent change in 300-3(b)which allows net current in NM when passing through non-metallic anything I think was a mistake and I hope it is remedied, since the Code is otherwise consistent in preventing induced current. Code deals with induced current (due to the magnetic field, of course) on the objects belonging to the circuit, but not on objects that are part of the building or furnishings or inhabitants.

However, rbj brought up the requirement that even if your boxes for NM are plastic, the circuits with net current still have to pass through a metallic panel. Are you going to cut slots in the panel? Can't violate UL requirements for the integrity of the box. Besides, you wouldn't anyhow.

So I think it makes more sense just to wire 3-ways with three-way travelers and forget about cutting slots, and you will never be called back, perhaps later on, to deal with a high magnetic field situation that someone with a gaussmeter finds in the building you wired, trying to save money with 2-wire.

Any comments on that slot business?

Karl
 
Re: 3 way switches

Hi Karl,

Ya, I'll comment. :) I think the metal box (at the service center) is not going to have a net current issue, as this is the branch circuit origination for the circuit that includes the threeway setup that is wired with 2-conductor NM. At the metal enclosure wall, the current going out on the hot equals the return on the neutral, seems to me.

Now, bear in mind, that same service center stands an excellent chance of being installed in a dwelling connected to a metallic municipal domestic water system. The GEC for the service is going to carry a significant percentage of any "neutral" unbalance current.

Who slots the service enclosure metal at the emergence of the GEC heading to the water service?
 
Re: 3 way switches

Al, we were writing at the same time. And I meant leukemia, not leakemia.

The NIH study was an interesting case of the false reporting of a study due to various interests. The study was written up in such a way as to test the idea that 2 mG would be associated with leukemia increase. The study found that though there was an increase it did not rise to statistical significance. This is what their press releases and summaries reported, and the NY Times and other papers took that and out came headlines that the EMF scare was disproved.

What the study sponsors were hiding was that the study did find statistical increases in leukemia at 3 mG and 4 mG. So the study actually verified the connection. Years later the scientific pressure lead to the study authors admitting this. But by that time the public had decided this was not a concern after all.

Why would the leadership of the NIH be involved in this? There is a little matter of intense competition for grant money for ones favorite projects. The tactics of political campaigns are typical of all bureaucracies unless you have a really good man at the helm.

The CA Health Service did a truly objective job of reporting the research. But I've said enough.

Karl
 
Re: 3 way switches

Al, we did it again!
I was refering to the case where the hot is taken from one circuit by the first switch and the neutral is taken from another circuit convenient to the second switch. Then you have two separate circuits with net current, requiring an impossible slot.

About the GEC to water pipe, I bet the Code panels never thought about that, since it was never actually planned that water pipes be parallel paths for neutral return.

Karl
 
Re: 3 way switches

Hal, I took a breif look at the link you posted and I'm happy to see that it seems to be an honest endeavor that lacks the propaganda that's often associated with the topic.

I agree that we should remove unnecessary stressors where we can. I quit smoking cigarettes 4 or 5 years ago, not cause I didn't enjoy them. In California we're told we can safely eat 1, 2 or 3 fish a year out of pretty much any of our waters. I'm not for that.

But I also don't want to live in a world designed by hypocondriacs. Perhaps it's unfortunate but when the news puts on some rediculous exageration, again, I'm inclined to dismiss that story and maybe a piece of what's real along with it. Not that there's no potential validity to the concern, there may well be. As long as the examination of the issue is rational I'm completely on board.

My last point is that we're all immersed in these fields, like you say, and I just don't see where we're all sucoming to the effects of EMF.
 
Re: 3 way switches

Uh oh, I've heard of you Karl. I just saw a whole bunch of new posts that snuck in befor my last post so let me catch up.
 
Re: 3 way switches

Hey Karl,

Ah, I understand which type of threeway you were thinking of. I was thinking of another variation.

A 14/2 NM branch circuit leaves the OCP and service, and goes to the first threeway. From the first threeway, a 14/2 goes to the second threeway, and a second 14/2 goes to the light. From the light, a 14/2 goes to the second threeway.

Think of a triangle with a light at one point, and a threeway switch at each of the other two points. The legs of the triangle are 14/2.

This is a "traveling bus" threeway, as Bennie coined it. The neutral goes in a loop from threeway to threeway via the light, and the hot goes directly from threeway to threeway.

The branch circuit can continue with a hot and neutral on more 14/2 extended from the second threeway.

A person in the room sits in the middle of a one winding air core electromagnet.
 
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