Three-way switch, multiple lights, used 12/3 throughout

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  #1  
Old 08-13-05, 01:54 PM
mainediy
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Three-way switch, multiple lights, used 12/3 throughout

I messed up. I have power coming in a switch box, then 12/3 from the switch to light one, 12/3 to light two, 12/3 to light three, then 12/3 to the end switch. Drywall is in and painted. I should have put two runs of 12/2 between each light. How can I rescue this situation without tearing apart the stairwell? The 12/3 is grounded - I guess I could use the ground as a fourth wire - which in turn probably doesn't conform to code. Any ideas?
 
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Old 08-13-05, 02:31 PM
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No, you cannot use the ground as a fourth wire. That would be wrong and extremely dangerous.

Your only safe solution is to redo the wires.

You should not have put two runs of 12-2 in place either. That would have also been wrong.

What you should have done is to use 12-3 from S1 to L1 and to S2, and the run 12-2 from L1 to L2 and then on to L3. Your other alternative would be to use 12-4 between the lights.
 
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Old 08-13-05, 02:39 PM
mainediy
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Ok, thanks. I was hoping for a less painful option. I could eliminate one of the switches, but it's a stairwell.

I got the idea for the double run of 12/2 from http://www.the-home-improvement-web....ch-option7.htm. Do you think that's not right? Irrelevant for me at this stage, though.

Could this be a possible fix? Run new 12/3 from L1 to S2. Then use the 12/3 in the wall between L1, L2, and L3 as 12/2 - just tape off the red wire in each of the other two light boxes. That would minimize the amount of drywall I would have to break into. Acceptable?

Thanks much.

Kelly
 
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Old 08-13-05, 02:49 PM
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You have a couple of choices beyond ripping out drywall. Keep in mind, however, that cutting and patching drywall is not such a big deal. It certainly shouldn't stop you from doing a _safe_ job.

If you have access to the switches from below (say from a basement), then you can run a new 12/3 between the switches. You use this 12/3 to create a switch loop, and then feed the lights from the first switch.

A third option is to use 'X-10' remote control devices. You use an X-10 switch at the first switch location, and then wire the lights as you would from a normal _single pole_ switch. Use the red wire in the 12/3 as an _unswitched_ hot, to provide power to the second switch location. At the second location you wire an X-10 transmitter. This looks just like a switch, but instead of turning a load on and off, it sends a command to the first switch, which actually turns the load on and off.

Good luck.

-Jon
 
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Old 08-13-05, 02:51 PM
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You can certainly run a new piece of 12-3 from L1 to S2 and then you will be fine. Tape off the unused wires.

The idea of running two pieces of 12-2 is not as bad or as wrong as I made it sound. You could certainly do this (if it weren't too late), and it would be safger than using a bare ground wire to carry current. Whether it would pass inspection or not is a different story. Opinions vary.

The issue is that the amount of current flowing one way in a cable is supposed to equal the amount of current flowing the other way. If you use two pieces of 12-2 then this would not be the case. Now if you run the two cables right next to each other, and run them through the same holes in the boxes, you more or less have the same cable
 
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Old 08-13-05, 02:54 PM
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I see that we crossed paths in posting. I'm repeating myself here, to address your second post.

Running two 12/2 NM cables side by side is _debatably_ allowed. It is clearly not allowed if you use any metallic wiring system (eg AC or MC cable), and it is clearly bad design if the two cables were to follow different paths. But many (myself included) are of the opinion that code would permit two 12/2NM cables run side by side, entering boxes through the same cable clamps (which must be listed for two cables), and that this is as safe as running 12/4NM.

Running a 12/3NM from L1 to S2 would work, as would running a 12/3 from S1 to S2 as I mentioned above.

-Jon
 
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Old 08-13-05, 03:16 PM
mainediy
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Thanks to both of you for the comments. Jon, I'm interested in the remote control switch. We're just finishing up a big rehab and the baby is due in just over a month - need to get this done! Have you heard any reports of interference due to wireless telephone or wireless internet routers? More technically, using the red as an unswitched hot - just wire screw that together in each of the boxes - then use the white between L3 and S2 as the neutral for S2? Assume that I would put the X-10 transmitter at S2. The black in that connection (between L3 and S2) would be unused.

So it would look like this:

S1 connected to L1 normally, black to black, white to white. At S1, connect the red to the black. At L1, connect the two reds together. Same at L2, L3. At S2, wire the red hot to the transmitter. Use the neutral connection between L3 and S2 for the neutral for the transmitter.

Hard to describe verbally. Does that sound right?

Thanks again, guys.

Kelly
 
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Old 08-13-05, 03:35 PM
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Kelly,

That sounds correct for wiring to get power to S2 for the X-10 device.

Just a personal preference, but I would use black as the always hot wire and red as the switched hot. Electrically it makes no difference and code wise either way is acceptable, but many people expect the red wire to be switched when they find a setup with black and red hot wires.
 
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