Induction in travelers?

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champion

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Location
St. Louis Missouri, US
Am concerned on engineering emt conduit for 3 and 4 way switches in a small commercial building.
The office area is only about 820 sq ft and the owner would like the lighting switched using snap switches from device boxes on three different entres in to the office.
Article 300.20 states information regarding induced currents in metal boxes and raceways.
I can route the 3way and 4way switches in a manner to include the neutral with the travelers to comply.
Maybe I am reading this too many times and am getting a bit apprehensive and concerned on which direction to take.
Lighting ckts are 120v.
Service is 120/208 3ph.
Any input would be appreciated.
Thank you
 
Re: Induction in travelers?

You don't need the neutral if it is a switch leg which is the two travelers and a return hot conductor. Either neutral or hot with the travelers is the usual way to run 3 way circuits and if you think about it you would have to go "out of your way" to do it with two travelers by themselves.

-Hal
 
Re: Induction in travelers?

As Hal says, you do not need a neutral to nullify induction or more correctly EMF.

Go HERE and check out "Threeway Switch Examples" A through E

Roger
 
Re: Induction in travelers?

Originally posted by roger:
As Hal says, you do not need a neutral to nullify induction or more correctly EMF.

Go HERE and check out "Threeway Switch Examples" A through E

Roger
Click to expand...
Note C and D use the white wire as a traveller. No bueno.

correction: C and D of the 4-way drawings use white as a traveller.

[ August 30, 2004, 01:38 PM: Message edited by: sdbob ]
 
Re: Induction in travelers?

On the three-way light switch examples A, B, D, and E are all incorrect and unsafe. He's switching white wires (travellers) and advising to "re-identify your hot white wires".
 
Re: Induction in travelers?

sdbob, that's not what we are talking about here. Besides, we've debated this to death. It's not incorrect or against the NEC to use the white as a traveler- reidentified or not. How else would you wire a 3 way switch leg as shown in "A"?

-Hal
 
Re: Induction in travelers?

Originally posted by sdbob:
On the three-way light switch examples A, B, D, and E are all incorrect and unsafe. He's switching white wires (travellers) and advising to "re-identify your hot white wires".
Click to expand...
OK, exactly what code section do you think is violated in doing this?

Roger
 
Re: Induction in travelers?

Never mind, :) Hal is right, this is not the discussion of this thread.

Roger
 
Re: Induction in travelers?

Hello Roger

I do appreciate you coming to my defense.And pointing members toward my web page.

As most of you that know me from my post no I make a lot of mistakes.Some times I post a reply without taking enough time to study the post and answer wrong from misunderstanding what the poster really said.

If I am wrong about being able to re-identify my white wires and use them as hots please point me toward the NEC art. that says you can not.

200.7 C1. says you can. also 200.7 C2. say they can not be used as the outlet or fixture return and, what the return is can be debatable.

But I think it means the conductor that leaves the last common on the last three way switch and terminates or hooks to the light fixtures hot lead? If you did this you would have the light fixture hooked to two white wires of course one would have either black tape or paint on it.

And this would be more confusing than need be.

Ronald :)
 
Re: Induction in travelers?

Strip your common and twist your travellers.Trim it the way it is roughed in. ;)
 
Re: Induction in travelers?

Allen, did you notice the mention of EMT along with a later mention of metalic boxes and raceways? :roll:

Would you simply trim out a device if you knew it were wrong?

Champion is questioning induction associated with incorrect wiring methods, not how to mark a common.

Roger
 
Re: Induction in travelers?

Hello Champion

I no you are aware of what the EMF or eddy current is and you no if you reverse your wire like in a switch loop and come back the other direction and the conductors are grouped together the magnetic fields will cancel each other out just the same as having a neutral running with them. As said you would have to go out of your way to generate eddy current.I no you don't plan on picking your hot up on one side of the room and your neutral on the other you will almost all of the time make a switch loop it is SOP. in the trade.

Ronald :)

[ August 30, 2004, 08:58 PM: Message edited by: ronaldrc ]
 
Re: Induction in travelers?

Thanks Hal

For pointing out the facts about the travelers.

Like I said sometimes I don't take enough time to read all the post thoroughly.

Ronald :)
 
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