3 way wiring method

[harrison]

I was told by an electrical inspector that a two wire wg romex could not be used for travellers in a 3way lighting circuit.The feed end and the switch leg end of the circuit are from a common source of power.Meaning the neutral is not from another branch circuit nor is the hot.Has their been a code change that I am not aware of.

 

[raider1]

Take a look at 300.3(B)

This requirement has been around for a while.

Chris

 

[al hildenbrand]

300.3 Conductors

(B) Conductors of the Same Circuit All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors and bonding conductors shall be contained within the same raceway, auxiliary gutter, cable tray, cablebus assembly, trench, cable, or cord, unless otherwise permitted in accordance with 300.3(B)(1) through (B)(4).

(3) Nonferrous Wiring Methods Conductors in wiring methods with a nonmetallic or other nonmagnetic sheath, where run in different raceways, auxiliary gutters, cable trays, trenches, cables, or cords, shall comply with the provisions of 300.20(B).

300.20(B) tells us how to handle metal j-boxes, but if you are using nonmetallic boxes with your 3way switch setup, then 300.20(B) doesn't apply.

If your inspector is using the NEC for the basis of his statement, he is not applying the above language. The NEC permits using 14/2 to run travelers between 3ways.

That said, there is an entire body of scientific study that is dedicated to documenting the human physiological effects caused by exposure to electromagnetic fields.

The The Electric and Magnetic Fields Research and Public Information Dissemination Program run by the National Institute of Environmental Health Sciences has a lot of information. There are other collections of information beside the Federal Government.

Wiring techniques like this 14/2 3way switch hookup leave unbalance electromagnetic fields of varying concentrations in the dwelling. But this is not a NEC issue.

 

[don_resqcapt19]

When you look at 300.3(B), make sure you read 300.3(B)(3).
Don

 

[dduffee260]

I think this is a common mistake with alot of electricians who have learned " on the fly" so to speak like they way I learned years ago. People who have been in a IEC, Union or some type of theory classroom know that this actually creates inductance with the travelers.

This mistake is almost as common as running the grounding electrode conductor through a cut off piece of EMT conduit without bonding the end of the conduit.

I myself made small errors such as this along with countless others until a few years back.

 

[harrison]

3 way switching method

3 way switching method

I would have to disagree about inductance being created in a nonmetalic sheathed cable.Of course I have only learned on the fly for thirty years.

 

[al hildenbrand]

Personally, having read a lot of the scientific literature, I am convinced that there are physiological micro-effects to the human body from low level 60 Hz electromagnetic fields that one can experience in common single family dwellings wired by methods such as K&T and NM configurations such as the 3way described above.

I believe our understanding of the micro-effects to the macro being is far from complete.

I personally choose to do my wiring in every possible way, that the NEC permits, that minimizes low level EMF.

 

[gndrod]

While I too have been guilty of two wire traveller wiring, I have gotten a fair input from RFI-EMI instruction and actual demonstration of two wire coupling that can drive you crazy when listening to an AM station and turning on a 3-way lamp that cross-couples as static on the same circuit. Sounds just like fluorescent lighting. "[404.2(A)] Exception: Switch loops shall not require a grounded conductor." DO NOT BELIEVE IT.

 

[gndrod]

Hi Al,
The medical profession has not found a way to make money on magnetic field health issues yet...but evientually our suspicions will be qualified by science. I remember a long ago thread that included the 3-way, four way switch question and I was introduced to Karl Riley and his in-depth book on TRACING EMF's. It is a great read and a field of it's own for making big bucks for many industries that are crippled by unwanted net current conditions.
If I remember, you were a part of that forum discussion.

 

[al hildenbrand]

I've never been one to shy away from this topic.

 

[roger]

Al, that may be a little understated.

Roger

 

[al hildenbrand]

Roger,

LOL

 

[A/A Fuel GTX]

Wiring techniques like this 14/2 3way switch hookup leave unbalance electromagnetic fields of varying concentrations in the dwelling. But this is not a NEC issue.

Excuse my ignorance on this topic but when travelers are run along with a grounded conductor, as in a 14-3 between 3 ways, the problem is eliminated?

 

[al hildenbrand]

the problem is eliminated?

Essentially, yes. With respect to the load controlled by the 3way switches, if the current that is on the traveller returns in close physical proximity (inside the same cable) then the net magnetic field around the cable is zero.

There are still ways to wire a 3way that will defeat this. If I cross neutral two circuits, for example, I could have other current in the 14/3 that results in a net magnetic field.

The basic image I hold in my mind as I'm laying out and later hooking up my branch circuits is that at any one cable or raceway on the circuit, for non-fault, normal loading operating conditions, the current going toward the load and away from the load is equal, just in opposite direction.

It is quite practical, in my opinion, to wire all my branch circuits so they generate zero net magnetic field.

Once the Premesis Wiring unbalance current passes into the Main Bonding Jumper, all control to do zero net magnetic field is lost.

 

[LarryFine]

In the case of the original post, running the traveler 14/2 along with the feed 14/2 would be tantamount to having a 14/4, and is how I always run them. Since the hot and neutral land in both boxes, running the travelers along the same pathway would effectively couple them.

 

[gndrod]

and other parallel high current cabling....