Just putting everything on an AFCI does not make the improper wiring OK. The neutral and the ground should not be following a different path to the source than the ungrounded conductors.

Further, not only is it improper to splice into other circuits, if your circuits are on an AFCI or GFCI, I will guarantee they will trip. They are designed to detect such faults.

All this butchering of the K&T likely problematic. I don't know what you've been doing, but there are specific requirements for interfacing between the K&T and other wiring systems. You can't just treat K&T conductors like they were individual wires from other cable/conduit systems.

I wouldn't jump to any conclusions. All the other k&t in the home was replaced by 12ga Romex, and so only two circuits that are ceiling lighting remain. There is no hack job work on the k&t, anything that could be removed was, and the other stuff that would require significant construction was left, which is why it's only ceiling lighting. Observing what is up there indicates that it's in very good condition with insulation, etc all fine.

The neutral coming in from the other side of the room from the hot implies nothing about connectivity to the source. K&t was always physically separated during installation, at least by a joist, if not more. It's more the fact that two other k&t switch loops that I CAN rewire to Romex will be, so that neutral could be removed if there was a way (the other loads will have their own, new, neutral and grounds).

I get it that k&t shouldn't splice in with Romex. But it is not possible to replace the travelers from one switch to the other from k&t to Romex. Since the k&t is in fine shape and has far lower loading then the design due to use of cfl and led vs incandescent bulbs, I have to leave it. It is on an AFCI and it doesn't trip and has worked perfect for 90 years. Practically speaking it's less than 500w with all connected loads operating.

So my options are:

1) Leave it all as is. Other loads on the neutral will be removed and rewired, and so the only thing on the k&t will be this one original three way switch setup for the one light

2) leave the two travelers to the one three way switch as k&t as-is, and only connect between the switch and the fixture with Romex. Thus I'm not splicing k&t directly to Romex, but instead they connect via a switch. Yes, the neutral would be separate and in the Romex, but it's no different than a neutral being a separate k&t runner as it is now... Only difference is that it would in fact be shorter than currently, so line impedance back to the source would be less, and the fixture could have a ground.

3) abandon the circuit and only have a single two way switch for powering that light (this option is unacceptable).

4) another idea compliant with 2014 NEC and any other best practices, for which im all ears.

Thanks!

I guess if you don't give a rats ass about the code you can do whatever the hell you want. I told you why you can't do it the way you want. The fact that you have an archaic existing installation is not justification for breaking the rules on the new wiring.

Settle down. I wouldn't be asking any questions if I was just going to wire nut whatever I felt like together and let it go.

Since when is use of remnant k&t outlawed by the NEC? Last I checked, there's no section that says that all sections of k&t must be ripped out to completion. And given it's ubiquitous nature, that's why it is still addressed in the NEC. There certainly is basis I've seen to convert k&t circuits over to GFCI protection in accordance with 406.3(D)(3)(a),(b) & (c) per my recollection. However given the real concerns with k&t being bad, old insulation, we went with AFCI though I'd change them over to GFCI tomorrow if that's better (outlets that were fed by k&t, all of which are now gone, did have GFCIs).

So understand I'm not breaking any rules with this three way switch situation because I've done NOTHING yet. I can leave the existing installation in place and it's perfectly fine. Or, if there is a way to make it better, I would.

But the run of the travelers is long and all our walls and ceilings are plaster and lathe, so making a million holes to run romex is a non starter. Given the location of the one switch, I can't pull romex from the basement or attic.

I'm sorry, but I have to imagine a better solution then abandoning it or making a total mess of my ceilings and walls to satisfy the run, is possible. What it is and doing it right is why I'm asking the question.

This post was edited by JHZR2 on Sat, Sep 13, 14 at 20:17

It's not the remant K&T that's the issue. It's your insistance that it's OK to just willy nilly connect things to random neutrals seperate from the hot feeds.

I would suggest getting an electrician with a clue. Most know how to pull wires without making "a million" holes in things.

You've not provided any indication of just where the wires that feed the two switches that you're talking about are, but NO you can not bootleg grounds and neutrals from other branch circuits, and no you can not run the grounds and neutrals in different cables EVEN if they run to the same AFCI breaker.

Thank you. I never insisted that anything is OK, just had a thought. Reason being that the rest of the loads off of that k&t will be rewired while the ceiling is down, so if I can get rid of at least the wire from the output of the three way switch to the fixture, then there would be no k&t in the kitchen.

I can appreciate the neutral issue, though the hot and neutral k&t lines are already separate. And, it wasn't clear that swapping romex on the other side of a switch would be a violation of nec 394, since I'm neither extending it nor splicing it together, rather just replacing one conductor type from one screw on the switch to the fixture which is already a circuit in place and in use. The neutral, if there was an acceptable way, would actually be reduced in length. Oh well.

I've had two electricians come by and both have indicated that the location of the one switch at the top of the stairs, given how the ceiling below goes and how the wires must be run, will be impossible without a good amount of damage. It's essentially three right turns in a very small amount of space which causes the issue. The other switch isn't a problem at all... Which is why the common to the fixture would be great to replace, same for the neutral. Travelers I can't help, neutral it would be nice...

But I guess I'll have to leave it all in there, in place.

Thanks for your time.

And I'd like to add one other thing to my overall question. So the entire knob and tube run is pristine. Very good condition, very nice Everywhere I can see it running (through part of the ceiling joist cavity in an open frame construction). I'm just going to leave it alone because I can't get new Romex up there.

But our kitchen is attached to the backside of our foursquare house and as a result there is actually an extension off of the home that extends the kitchen out a little bit further. It was original and since it was original there's no insulation in the ceiling.

The lighting fixture as well as the entire three-way switch loop is all completely in open uninsulated cavities which are compliant even according to the latest NEC. However we would like to be able to put insulation into the other section where there is just a hip roof above the ceiling. When the ceiling is up there will be no access which I know is a parameter in the code.

I know that you cannot run knob and tube around insulation or have insulation over it even though in some states apparently there is a waiver. So I'd like to try to figure out a workaround again since I cannot rewire the connections to the fixture with romex what choice do I have?

Is it possible to at minimum install conduit above the insulation with a new single neutral wire that connects to the knob and tube in two places? In other words just replace one section of the existing run so that it is protected from insulation that we would want to put up there?

Optimally I would relocate the neutral and shorten its length, but cannot do that due to the restrictions of splicing in romex. There will be no other loads on the neutral because I will be re-wiring all of the others with new Romax from the basement. It's only this one stupid lighting load on this three-way switch.

Thanks for your guidance!

wireless 3 way switch.... problem solved.

Conductors of the same circuit must be contained in the same raceway or cable. Knob and Tube was not installed this way which is why it can generate inductive heat while in use. Anything you do now must be to current code, which doesn't let you do what you are proposing.

This post was edited by joefixit2 on Mon, Sep 15, 14 at 0:15

Yeah. There is the 'special approval' clause in 394.10, I believe, so I'll have to check directly with the inspector.

We did another consult with a specialist in k&t removal, traced the run and looked at the architecture and walls. Lots of damage to replace this one, so in it will stay. I have a good basis to be able to use the switch with less than 40w on it if needed, so we will see if they allow the special approval condition.

If not, it stays in place.

Another option would be to just replace one section of the neutral line, to be rerouted. If it has to be a k&t run, which seems to still be acceptable up to at least some year in 394, then so be it.

The worst condition in terms of load and length is what it is now. I'll definitely be removing two loads from the k&t circuit, which also reduces overall system length. If I can do some refitting of the remaining neutral, I guess that's ok (and probably expensive to splice in properly), or whatever the inspector says.

What a convenient yet completely inconvenient place to put a switch!

Thanks!

I was being quite serious when I said wireless 3 way. I've used them many times in situations where I wasn't able to get wiring where i needed to easily.
You stated you can legally have a single pole switch, if that's the case than more than likely you can add a wireless 3 way system.
In any case, it seems like you're quick to dismiss any advice people are trying to give you so I'm a little confused what you're even doing here? Trying to get justification?

"In any case, it seems like you're quick to dismiss any advice people are trying to give you so I'm a little confused what you're even doing here? Trying to get justification?"

Im not dismissing anything. Ive tried my best to describe the situation, which unfortunately is more unique/involved than others. We pulled a TON of k&t out of the home and took it all up to NEC 2008 spec (code at the time). It was all completely removed. What is left is overly difficult to remove, yet highly functional and necessary. Im not looking to skirt anything for the sake of doing things haphazardly, I just have a tough situation here to fix while I have the opportunity.

Again, I wouldnt be asking questions if I was just inclined to wire nut some romex to some K&T and call it a day.

I think I mentioned about using CFL and LED. We also want a dimmer on the switch closer to the fixture... And it has to be a suitable LED/CFL dimmer, which Ive not seen in the wireless 3-ways (maybe Im wrong, Ive gone through the leviton products). So unfortunately there are more dynamics in play here that get overly wordy (Im already wordy enough in these posts).

I have to imagine that someone, at some time, had to repair a section of K&T wire, and did so. I dont see anything in NEC 394 against that, and NEC doesnt prohibit k&t from remaining in use. I get it that most everyone doesnt do much with it besides remove it, but if Im not expanding the system, and just trying to move or address one conductor's location (a non-switched neutral), I just hope that there are other options. I want to be as educated as possible...

Thanks!