# Anyone else seen a magnetic field issue caused by 3-way switch wiring?



## Electric_Light (Nov 25, 2007)

For a three way switch to work, there are two hot wires that need to be connected between the two switches. I guess some electricians don't see the need to keep the two wires physically together with the neutral.

An AC current flowing through a wire creates a magnetic field. This is how a current clamp meter measures the current by clamping over ONE wire. If you clamp both the neutral and hot together, you'll get a reading of 0 because they cancel each other out.

So, in a house I once lived in, I had a problem with my CRT monitor rippling whenever the chandelier over the stair was turned on. Apparently, there was a run of wire behind the wall behind the CRT that wasn't in a pair creating a magnetic field that didn't cancel out. 

The magnetic field of 3A flowing through a wire isn't all that strong, but if there's a run of neutral or hot that isn't run in a pair near a CRT, it's enough to cause a ripple on CRT.


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## Bkessler (Oct 8, 2005)

Crt?


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## Electric_Light (Nov 25, 2007)

Bkessler said:


> Crt?


TV and monitors using traditional glass tube, that is sensitive to external magnetic field.


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## bwalley (Jan 7, 2009)

Bkessler said:


> Crt?


Cathode Ray Tube.

The TVS and Computer Monitors we used to use before flat screens and LCDs.


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## Bkessler (Oct 8, 2005)

thanks!


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## Celtic (May 23, 2007)

Bkessler said:


> Crt?


1998 called....they want their monitor back:










:laughing:


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## Magnettica (Dec 19, 2006)

I had no idea what the OP was talking about either. But I don't have to wonder about that because this is how I roll...


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## acrwc10 (Dec 10, 2006)

Magnettica said:


> I had no idea what the OP was talking about either. But I don't have to wonder about that because this is how I roll...


 So you are really "MAC-nettica" . Are you one of the X-men ? 

back to the OP, Nope never had an issue with it that I am aware of. You would need a Gauss meter to trace out EMF in a building, know anybody that has one ? http://www.lessemf.com/gauss.html


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## Magnettica (Dec 19, 2006)

It's a beautiful computer. Intel Core 2 Duo processor, 1GB memory, 200GB hard drive, beautiful. I can edit digital movies, burn DVD's, download electrical PDF files, burn CD's, update the Ipod, and watch streaming internet videos all at the same time. How spoiled are we really?:thumbup:

"MAC" nettica - has a nice ring to it.


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## MALCO.New.York (Feb 27, 2008)

acrwc10 said:


> So you are really "MAC-nettica" . Are you one of the X-men ?
> 
> back to the OP, Nope never had an issue with it that I am aware of. You would need a Gauss meter to trace out EMF in a building, know anybody that has one ? http://www.lessemf.com/gauss.html


Holy Fookin' new i Tuuunez!


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## jrclen (Jul 10, 2007)

Electric_Light said:


> So, in a house I once lived in, I had a problem with my CRT monitor rippling whenever the chandelier over the stair was turned on. Apparently, there was a run of wire behind the wall behind the CRT that wasn't in a pair creating a magnetic field that didn't cancel out.


It is pretty common for a DIY type to use 2 runs of 14-2 for a three way circuit rather than a 14-3 between the switches. And it makes perfect sense to them to use one cable for the 2 travelers, and the other cable for the neutral.


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## macmikeman (Sep 12, 2005)

Magnettica said:


> I had no idea what the OP was talking about either. But I don't have to wonder about that because this is how I roll...


Ahh, now ther's a sparky after me own heart......:thumbsup:


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## jrclen (Jul 10, 2007)

Magnettica said:


> I can edit digital movies, burn DVD's, download electrical PDF files, burn CD's, update the Ipod, and watch streaming internet videos all at the same time.


How do you find time to work? :laughing:


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