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crescere 09-07-2012 10:17 PM

3 way switch layout has me confused
 
I am confused about how to wire a three way switch set up. According to a book I use the power comes into what I will call switch 1. In switch 1 box the power in black wire goes to the black nut on the switch, and the power in white goes out through switch box 2 and to the light. A three wire cable leaves switch box 1 with the black connecting to the switch and the red connecting to the switch. Switch box 2 receives the three wire cable and also the black goes to switch 2 and the red goes to switch 2. A two wire cable leaves switch box 2 and goes to the light. I am sure this is standard. If I confuse you please just read the last paragraph.

MY scenario is backwards in that the cable going to the lights comes out of what I called switch box 1 above. The downstairs switch only has a switch and a three wire cable inside it. The switch box on the second floor has power coming in and a cable going out to the lights. It seems like no matter how I think about this I do not know what to do with the white wire in the downstairs switch box. Right now my upstairs box has the white wire from the three cable going to the switch. Shouldn’t that be the balck wire?

There is probably an easy solution to this. Can someone print one of those helpful diagram layouts depicting my scenario? Again, the downstairs light box has only a three wire in it, but the upstairs has: a) 2 wire cable with power coming in, b) two wire cable going to the light, and c) 3 wire cable coming in from downstairs. The lights themselves are mounted to the upstairs ceiling directly above the staircase.

parman 09-07-2012 10:54 PM

Quote:

Originally Posted by crescere (Post 1005291)
Can someone print one of those helpful diagram layouts depicting my scenario? Again, the downstairs light box has only a three wire in it, but the upstairs has: a) 2 wire cable with power coming in, b) two wire cable going to the light, and c) 3 wire cable coming in from downstairs. The lights themselves are mounted to the upstairs ceiling directly above the staircase.

Does This help? Sounds like your situation

http://www.justanswer.com/uploads/El...n_same_box.JPG

frenchelectrican 09-08-2012 12:27 AM

As parman above me posted that what we called them is " three way switch loop " and it is pretty common one to see however there is one major gotcha you have to remember is that you will have to remark the white conductor with black tape or marker ( I useally use Bleu marker ) so you know that is the traveller not the netural.

And make a note I am not sure if that did show up in drawing or not but on most common three way switches they will have a dark colour screw or marked common or " C " one of the three then you will see two bright brass screws that is your traveller as in the drawing either remarked white et red can land either one.

( only time you will do the spefic way if you have timer or multi location dimmers then you will have to refer to the instruction on them )


Merci,
Marc

crescere 09-08-2012 03:13 AM

Thank you . That is very helpful and an impresive answer. The colors really help.

parman 09-08-2012 09:37 AM

Quote:

Originally Posted by crescere (Post 1005379)
Thank you . That is very helpful and an impresive answer. The colors really help.

I was in a hurry and found that pic on google. It looked like it matched your situation so I posted it.

I did not tell you, if you did not already guess, is that at each switch, the black wire is attached to the common or dark colored screw. Between the two switches, the red and white go on either of the silver screws, it does not matter which screw on which switch.

As posted above, the white that travels between the two switches, should be remarked as a black wire. Tape, marker, whatever you want. Just so there is no confusion later.

I don't know why, but some people get all :eek: when they see a white wire and it's not a neutral or grounded conductor, but is actually part of a switch loop which carries current.

Rochsolid 09-08-2012 11:26 AM

I find the easiest way to wire 3 way switches is as follows:
Power feed to switch 1
3 wire from switch to switch
Feed to light from 2nd switch

To make your joints.
In first switch box:
Power coming in goes to your "common" screw, your black and red from the 3WIRE will be
Your travelers.and all your whites will be wire nutted together.
In 2nd switch box:
The black going to YOUR LITE will go on your "common" screw, and the black an red from your 3WIRE will be your travelers, an all white's will be wire nutted together.
In your lite box, black to black and white to white


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