K&T / NM wiring

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Old 08-31-09, 08:16 AM
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K&T / NM wiring

Hi again everyone,
I thought I would post this first, because I've had very limited exposure to K&T wiring. I'm working on some rooms by tearing down plaster and replacing it with new drywall. Where I could remove old knob and tub wiring - I have done so replacing it with various 15A and 20A lines for various switches, lights, and receptacles. I've done enough wiring that I'm very confident that everything I've done has been in line with code, etc. Please keep in mind that the work is happening on the 1st floor, so having basement access has meade removing the K&T wiring certainly easier, as well as running new NM cable etc. By question is as follows:

I have a 3 way switch located at the bottom of the stairs to control a light. Obviously the other switch is at the top of the stairs. While the wall was opened, I noticed that there were 3 lines coming into the box. 1st question - a 3-way switch with a total of 3 wires, would make me think that they would all be "hot".... typically,there would be one hot "black" coming in, and two leaving, normally one black and one red when I use 14/3 cable. Is is correct that there is no neutral nor ground. I would love to replace this with 14/3 but I don't have access to the 2nd switch and light source. So, what's the best path.....

To complicate this a little more, I want to include that 3 way switch located at the bottom of the stairs in a 3 gang PVC box. The other two will use brand new wiring...so they should not be an issue.

Should I just take the K&T and feed them through the PVC box and basically reinstall it in teh same exact way it is now? I've read the teh "insulation" around the K&T wiring can be flimsy...so, would it be a good idea to wrap it in tape first?

Any assistance or guidance would be greatly appreciated.

Thanks,
Mark
 
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Old 08-31-09, 08:30 AM
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Originally Posted by miwankiw View Post
I would love to replace this with 14/3 but I don't have access to the 2nd switch and light source. So, what's the best path.....
The best (and only legal) path with K&T is complete replacement with new wiring. You can leave it as-is in which case it will be grandfathered with no modifications of any part of the circuit; or you can disconnect it and completely replace it.
 
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Old 08-31-09, 08:35 AM
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Thanks Ben...
If I were to find that the source was coming in from the basement, could I essentiall remove the srouce there and just leave the residual K&T in the wall and somehow just run the correct woring from there. I just want to make sure what constitutes complete replacement.

BTW - where is the neutral wire typically? I had another location that had two distinct K&T wires going into an outlet, so it appeared that there was a neutral there, but I can't seem to find anything that remotely looks like a neutral on the switch line. Should I be able to find something coming from the panel...and if so, should I disconnect/ remove too?
 
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Old 08-31-09, 09:47 AM
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Anywhere power is consumed (receptacle, light fixture, etc) will have a neutral. Switch loops often have two hots (in new installations the white wire is remarked as black) and no neutral. At 3-way switches, the switch loop is 1 hot and 2 travelers (also hot). So it is common to not see a neutral at a switch location, whether it be single pole or 3-way.

Note that K&T wiring often includes "creative" wiring practices, so when replacing it, don't assume that the wires are connected the way you would think.
 
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