3 way switch and power.

[rgiraldo]

ok if you only have 12/2 to complete the a run for a 3way switch, the answer to your question is no. The code require that all wire for the run be together. Remember that the grounded conductor cancel out the emf (flux).
Heat heat heat heat

 

[mivey]

I thought you were commenting on this post:

If you feed the 3-way at one end with a hot and switch at the other end you can use one 12-2 using the black and white for your traverlers. This will work just fine.

I was. But he was responding to the bold part of this post:

...In otherwords if I had a 3 way in a small bathroom and i didn't have any 12-3 could I just use 2 12-2's and cap one off?? Thanks..

I read the response a couple of times and just had a problem convincing myself someone was suggesting using only one #12-2, even though that was how I read it at first. After Bryan's post I read it again and thought maybe I was taking the post too literal. I was trying to allow for some kind of typo/wording issue.

The OP was talking about using 2 12-2s (which can be ok if handled correctly). I thought the response might be read two ways:
1)"...you can use one of the 12-2's using the black and white for your travelers and use the other 12-2 for the neutral/feed/return..."
2)"...you can use just one 12-2 using the black and white for your travelers and eliminate the other 12-2..."

I was hoping he meant #1. With #1 the EMF and inductive issue can be controlled. With #2, you can't win.

 

[quogueelectric]

It would depend on the separation between the two 12-2's. Also, this separation can be an issue if there is ferrous material involved.

I see no problem as long as the two 12-2's are kept together. When doing this, I usually lightly twist them together throughout the run to make sure they stay together. This reduces the chance of something ferrous getting between them and causing inductive heating.[/Q All messed up please delete me

 

[mivey]

ok if you only have 12/2 to complete the a run for a 3way switch, the answer to your question is no. The code require that all wire for the run be together.

I disagree. It is ok per 300.3(B)(3) as long as 300.20(B) is followed.

Remember that the grounded conductor cancel out the emf (flux).

Or a wire running in the opposite direction carrying the same current (like a switch leg). Cancellation is not limited to the neutral.

 

[mivey]

...All messed up please delete me

Please note:
Quogueelectric has been deleted.:grin:

 

[K8MHZ]

I don't see how EMF would be a problem, it would be no different then just bringing down a hot and switch leg to a single pole switch.

EMF???

EMF is voltage.

I think you all are discussing inductive heating.

 

[al hildenbrand]

EMF???

EMF is voltage.

I think you all are discussing inductive heating.

Besides Electro Motive Force it also means Electro Magnetic Field. Gotta rely on the context for the clue.

 

[K8MHZ]

Besides Electro Motive Force it also means Electro Magnetic Field. Gotta rely on the context for the clue.

Even so, it's not the electromagnetic field that is responsible for the heating, it is induction.

Take a look at 665.2, definition of inductive heating.

The heating exists because of a VARYING electromagnetic field.

DC also has an electromagnetic field around it. Since it does not vary, there exists no induction and therefore no heating.

 

[mivey]

Even so, it's not the electromagnetic field that is responsible for the heating, it is induction.

Take a look at 665.2, definition of inductive heating.

The heating exists because of a VARYING electromagnetic field.

DC also has an electromagnetic field around it. Since it does not vary, there exists no induction and therefore no heating.

Actually, two issues with a separated conductor were raised: EMF & inductive heating.

 

[al hildenbrand]

DC also has an electromagnetic field around it. Since it does not vary, there exists no induction and therefore no heating.

That's true only for stationary conductors in a steady electromagnetic field. Any conductor that moves, and, in moving, breaks lines of force, has currents "induced" in it.

 

[roger]

Even so, it's not the electromagnetic field that is responsible for the heating, it is induction.

Take a look at 665.2, definition of inductive heating.

The heating exists because of a VARYING electromagnetic field.

DC also has an electromagnetic field around it. Since it does not vary, there exists no induction and therefore no heating.

Leaving inductive heating out of the conversation, EMF (as in Electro Magnetic Field) also causes circuit noise and interference in electronic equipment and it is suspect in being a possible cause of childhood leukemia.

Running circuit conductors in a manner that will cancel EMF effects is a simple task.

Roger

 

[K8MHZ]

That's true only for stationary conductors in a steady electromagnetic field. Any conductor that moves, and, in moving, breaks lines of force, has currents "induced" in it.

You are correct. I used DC to illustrate that a field could exist sans induction. Movement would indeed cause a variation and thus the capability of induction.

I am just trying to make clear the reason for the heating. We are on the same track.

There are other ways to create induction with DC but I don't believe a discussion thereof would contribute to the thread.

 

[K8MHZ]

Leaving inductive heating out of the conversation, EMF (as in Electro Magnetic Field) also causes circuit noise and interference in electronic equipment and it is suspect in being a possible cause of childhood leukemia.

Running circuit conductors in a manner that will cancel EMF effects is a simple task.

Roger

I would like to see a link for that. RF always gets the blame for the above.

 

[K8MHZ]

Actually, two issues with a separated conductor were raised: EMF & inductive heating.

Gotcha .

 

[mivey]

I would like to see a link for that. RF always gets the blame for the above.

Take your pick:
http://www.google.com/search?source...&rls=GGLG,GGLG:2005-52,GGLG:en&q=EMF+leukemia

 

[al hildenbrand]

Leaving inductive heating out of the conversation, EMF (as in Electro Magnetic Field) also causes circuit noise and interference in electronic equipment and it is suspect in being a possible cause of childhood leukemia.

Running circuit conductors in a manner that will cancel EMF effects is a simple task.

I would like to see a link for that. RF always gets the blame for the above.

RF is a subset of EMF. EMF goes from DC to beyond Cosmic Ray.

In normal 60 Hertz power and light wiring, RF sources include contact bounce at snap switches, the AC contactor, the refrigerator thermo, etc., as well as any solid state device that has sufficiently fast turn on or turn off. The fast turn on or turn off will approximate a square wave edge, which can be full of RF.

Or did you mean you want to see a link to childhood leukemia?

 

[roger]

I would like to see a link for that. RF always gets the blame for the above.

There are a number of links in this thread that discuss studies and opinions.

You can also check out threads that Karl Riley has participated in for more discussions.

Roger

 

[LarryFine]

In normal 60 Hertz power and light wiring, RF sources include contact bounce at snap switches, the AC contactor, the refrigerator thermo, etc., as well as any solid state device that has sufficiently fast turn on or turn off. The fast turn on or turn off will approximate a square wave edge, which can be full of RF.

Let's not ignore contact arcing, especially when opening inductive-load current.