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Old 02-14-2010, 12:34 PM   #1
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3-way switch help


I need some help please. I'm trying to install a new hallway light with two three-way switches on either end. So in my gang boxes, here is what I have:

Switch 1:
12/2 wire that is the power source
12/2 wire that goes to the light
12/3 wire that goes to Switch 2

Switch 2:
12/3 wire that goes to Switch 1

Here is how I have the wiring:

In Switch 1 gang box:
  • The 12/2 white wire from the power source connected to the 12/2 white wire of the light
  • The 12/2 black wire from the power source connected to the Common terminal of the 3-way switch
  • The 12/3 white wire connected to the traveler terminal of the switch on the opposite side of the common terminal
  • The 12/3 red wire connected to the traveler terminal of the switch on the same side of the common terminal
  • The 12/3 black wire is connected to the 12/2 black wire to the light fixture
In Switch 2 gang box:
  • The 12/3 black wire connected to the common terminal
  • The 12/3 white wire connected to the traveler terminal of the switch on the opposite side of the common terminal
  • The 12/3 red wire connected to the traveler terminal of the switch on the same side of the common terminal
So my problem is when I turn the fuse back on, it immediately trips again. Like there is a short in the line. If I remove the 12/2 black power from the common terminal on Switch 1, the fuse does not trip (as expected since there is not electricity supplied to all the wiring). So there must be a short somewhere but I just can not figure out what I did wrong. I tried to wire the 12/2 power straight to the 12/2 light wire, bypassing all the switch wire, and that works fine. The lights get power. I testing my 3-way switches for continuity between the common and traveler terminals and everything seems to be fine with them.

Does anyone have any ideas on where I went wrong wiring this?

Any help would be greatly appreciated!

Thanks,

Amit

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Old 02-14-2010, 01:34 PM   #2
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3-way switch help


You need an electrician. The first really dangerous thing you did was use a white wire as a traveller. White wires are neutral or constant power only. The following is the correct way to make-up this type of 3way.

HOWEVER - THIS WILL NOT SOLVE YOUR TRIPPING PROBLEM! FOR THAT I STRONGLY RECOMMEND THE PERSONAL ATTENTION OF A QUALIFIED ELECTRICIAN.

Box 1

12/2 line (power) black WIRENUT to 12/3 white (tape white conductor with black tape)

12/2 line (neutral) white WIRENUT to 12/2 load (light) white (neutral)

12/2 load (light) black to 3way swith common terminal

12/3 red to traveller terminal 1

12/3 black to traveler terminal 2


Box 2

12/3 white to common terminal (tape white conductor with black tape)

12/3 red to traveller terminal 1

12/3 black to traveler terminal 2

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Old 02-14-2010, 01:48 PM   #3
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3-way switch help


I agree with R_T with regards to the white wire. But other than that, your wiring configuration would work fine just the same. So there is either a short somewhere, or you are not actually connecting your wires to the terminals as described. Maybe you are mixing up what you are calling the traveler and/or common terminals? Did you run the wire between the switches or to the light, or was that already there? If you ran it new, maybe you nailed in a staple too tight and broke through the sheathing? Or if you are using metal boxes with knock-out clamps, maybe you tightened a clamp too hard and broke through the sheathing?
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Old 02-14-2010, 04:32 PM   #4
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3-way switch help


Needs to be wired like this.

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Old 02-14-2010, 05:18 PM   #5
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3-way switch help


Joed, while that configuration will work, and may be legal in Canada, the NEC prohibits the use of a white conductor as a traveler.

It is only allowed to be used as a supply for the switch provided it has been re-identified, as outlined by R_T.

Code reference: 200.7(C)(2)
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Old 02-14-2010, 06:31 PM   #6
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3-way switch help


Thanks RT for the wiring layout. I agree with you, I am not a electrcian and am learning through my remodel as I go. I used the white wire as the traveler, but I did fail to mention that I did put black electrical tape on each end of it. I found my existing wiring layout in an How To electrical book and it showed using the white wire (with black tape on each end) as a traveler in my case.

adpanko - this is a new wiring and I did staple it down as I went. Is there a way to tell if I broke the sheathing on one of them and causing it to short out?

Thanks again for everyone's input and help.

Amit
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Old 02-14-2010, 07:43 PM   #7
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3-way switch help


If you wired like you said it should work for you, maybe you have a bad switch. Try takeing the wire off the switches, in the first box put the hot comeing in on the red wire and in the second box tie the red and black together. Leave the white wire loose and turn on your breaker.

If the breaker trips then you would have a problem in your 3 wire, if it does not trip trying putting the in comeing hot in box 1 on the white and then connect the white to the black in the second box. Turn the breaker on, if all is well i would say one of your switches is shorting out. If the breaker trips then the wire is bad.

Hope this makes sense and helps you get to the bottom of your problem.
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Old 02-14-2010, 08:22 PM   #8
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3-way switch help


Metal boxes with screw clamps? Check to make sure you didn't tighten the clamp too much and cut into the wire.

Quote:
the NEC prohibits the use of a white conductor as a traveler.
No, it prohibits the use as the return to the fixture. Using it as a traveler is within the context of using the remarked white wire as supply to the switch.
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Old 02-14-2010, 08:59 PM   #9
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If you still have access to your walls, check each staple and if there is an instance where you tightened it down too far and broke the sheathing (thus leading to the staple touching bare metal wire), you will likely see a little burn mark at that staple. And check for the same burn marks around your knock-out clamps, if you used metal boxes and clamps. If you used plastic boxes, you most likely don't have any sort of clamp where the wires come into the box (though certain plastic boxes have integrated clamps built in)
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Old 02-14-2010, 09:13 PM   #10
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Hi Adpanko, I'm pretty sure my 12/3 wire is shorting out somewhere. Either on a staple or a metal box knock out clamp. I followed Darren's advise and tested it without the switches and the fuse still blows whenever I'm tied into the 12/3. Thanks Darren for the tip on testing the wires. I guess I'll spend some time tomorrow cutting out drywall and tracing the 12/3 wire back to the source to see where I nailed or tighted too much. Thank you all for your assistance in tracking this down... I'll post what I find tomorrow.
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Old 02-14-2010, 11:58 PM   #11
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If you are using a handi box (small metal single gang box) and you are entering the top or bottom of the box, check to see if the screw that holds the switch to the box is a bit long and making contact with the conductors.

I don't really care if the NEC allows use of a white conductor as a traveler or not. If you have a white wire that is used to carry power and it is not hot all the time, it can fool people. Fool people with 120v and you might have a serious mess to clean up. BTW, it wasn't very long ago the NEC allowed you to put a receptacle in a shower enclosure. Let common sense prevail.

FWIW -It only takes about 0.02 amperes of current passing through the body to make it impossible to let go of the source. That doesn't sound like much and it isn't but it is 10 times what is needed for "shocking" to begin. By the time current reaches about 0.1 ampere you're likely fixin to die. The body conducts quite well but skin is a pretty good insulator. That's why electrical current has to blow big hunks of skin out of the way so the electricity can reach ground. Thus, the mess.
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Old 02-15-2010, 08:58 AM   #12
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Quote:
Originally Posted by kbsparky View Post
Joed, while that configuration will work, and may be legal in Canada, the NEC prohibits the use of a white conductor as a traveler.

It is only allowed to be used as a supply for the switch provided it has been re-identified, as outlined by R_T.

Code reference: 200.7(C)(2)
I disagree. Power is being applied to the first switch. The black from the second switch is being used as the return from the switch. Therefore the white is properly used as a supply to the switch.

Also this is not a switch loop situation. Power is not at the fixture. It is at the switch.
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Old 02-15-2010, 01:31 PM   #13
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Quote:
Originally Posted by kbsparky View Post
Joed, while that configuration will work, and may be legal in Canada, the NEC prohibits the use of a white conductor as a traveler.

It is only allowed to be used as a supply for the switch provided it has been re-identified, as outlined by R_T.

Code reference: 200.7(C)(2)
I've read the code referenced, and I'm a bit confused by its wording.

With some paraphrasing, here is what I think 200.7 says as it relates to a 3-way switch:
A white insulated conductor can be used as other than the grounded conductor where it "is used for the supply to the switch but not as a return conductor from the switch to the switched outlet."

The last part, "not ... to the switched outlet" makes it sound like you me that you CAN'T use the white wire as a return (and therefore you can only use it as a traveler). But then the code also talks about it can be used to supply the switch. But I'm sitting here thinking a "supply to the switch" would be the cable that provides power from the circuit breaker to the common terminal in the 1st 3-Way switch (which clearly need to be a black wire in a 2 conductor cable).

Can someone help decode the "code-speak" that 200.7 is using?
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Old 02-15-2010, 01:48 PM   #14
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In a 3way/4way setup using 3 conductor cable, the white may be used as a traveler or as the constant hot common; in a switch loop setup (power enters at the fixture) the white is used to supply power to the switch; in either case, the white should be re-identified.

The white may NOT be used to supply switched power to a switched fixture.
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Old 02-15-2010, 02:23 PM   #15
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So after cutting some holes in my drywall, I found the problem. It was as many of your have mentioned. My clamp on the metal knock-out box was tightened too much resulting in it breaking the sheathing and causing the short on the 12/3 wire. Luckily, I left enough slack on the 12/3 in the wall that I was just able to cut the wire at the clamp and pull though enough to make new splices. After that, I rewired the 3 way switches as R_T suggested and lights work!!

Thank you all for you input and suggestions in helping me resolve this issue.

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