Electricians out there? Knob and Tube question

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trivetman

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Jul 14, 2017
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Jenkintown, PA
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Hi all -

I had a light flickering in my hundred year old house. I figured it was just a bad switch but replacing that didn’t fix the problem. a little more digging...turns out there is still knob and tube in my house!!!! YAY!!!

All other fixtures on this circuit are working no problem and test at 120 volts. The one light which wasn’t working so well tested at only 60 volts at the switch. No idea what is behind the voltage drop - I assume a bad connection somewhere along the line.

As of now I’ve just cut the old switch and fixture out and capped the wires. I think my best solution (that doesn’t involve major renovation) is to rewire this one fixture from another nearby circuit (modern romex) and just leave the K&T capped and in place. This would leave hot K&T in my walls but without current running through the faulty part. I think this is a reasonably safe solution.

I am planning on calling an electrician about this. But there’s a lot of smart people on this forum so I thought I would put it out there.
 
Pulling a new line off another box is a good ideal.
I would try and trace the source for the K&B and kill it there.

K&B is actually alot safer then most people think. One of the biggest risk is when it is or gets buried in insulation.
 
I’m not that worried about the KT which is working well. Its only powering a handful of low wattage CFL’s. Now that I know about the wiring I’ll avoid running the vacuum off those outlets.

Its not possible to kill the faulty KT at the source without it being a major renno. Itll probably mean a lot of holes in the ceiling and walls to find how it connects in. It would probably also kill some downstream fixtures which are working fine and powered by the same KT branch. That might be a major rewire to reconnect with romex
 
As long as its not covered in insulation you should be fine.
Another thing to check would be were it comes into a box. If the wire insulation is intact ok, or cracked/dryed out then it would not be safe.
Were I am we are not allowed to use romex or bx, only conduit.
There is no code saying it has to be-removed that I am aware of, but most of the towns if not all in the Chicago-land area make us remove it.
 
Thanks. Insulation isn’t an issue. Its in a ceiling between floors.

I cant find the source where the KT is being powered. Everything coming out of the breaker box in the basement is romex or conduit and running up into the walls.

There’s a couple old light fixtures in the bathroom which I can’t get open without destroying. I suspect behind one of them is where the romex meets KT. What I can see in the ceiling the insulation around the KT wire seems ok. Not cracked.

sounds like I’ll probably be safe with this plan. I’ve got an electrician I can call on Monday.
 
Wires connect and terminate in junction boxes, not inside closed off wall or ceiling spaces. It is not always obvious why codes exist, and applying your own logic to guess at the possible scenarios isn't particularly prudent. Ring and tube doesn't always connect in boxes, but they don't do it that way any more for good reason. Somebody's house burned to the ground because they did what you're about to, so they came up with a building code to prevent it from happening again.

Still not convinced? So g-forbid your house should ever catch on fire, for any reason. When the insurance adjuster comes through your ashes to determine the cause of the fire, and finds your handiwork, you're gambling your six-figure settlement that he's going to see things your way. Part of his job is to find an excuse not to pay out, don't give him any extra ammo.

Do it right.

What are we talking? Plaster? Sheetrock. Lath? None of it is that hard to patch and paint. It's not "major renovation." I'll walk you through how to do it easily if it comes to that.

Terminate the ends in a box. What did you cut? Are they cut too short to terminate inside the box you'll use for the new switch? Then move the box in the direction of the wires so that they can reach the box. Patch whatever hole is left. I've done some seemingly impossible electrical renovations with Old Work Electrical Boxes, a fish tape and a few small holes in the wall.

If you haven't done the work yet, post a pic and maybe I can give you a better solution.

And frankly, I'd be more concerned about the voltage drop. That's got trouble written all over it. Back to the insurance scenario... if that drop is resistance along the line, which means heat, which could mean fire, and the adjuster puts together that you knew about the problem and buried it in a wall without fixing it... Well, I'd say "Do the math..." but there won't be any math...

Excuse the doom and gloom, just giving you something to think about...
 
Dirk,
I hear what your saying, thus reason I pointed out, when we come across it here, they make us remove it.
I assumed when trivetman said he capped the wires and left them, they were in a/the switch box.

He did say he was calling an electrician, so I did not get into the voltage drop.
Knob and tube, many times the neutral was switched, not the hot leg, there could be back feed on the neutral side,
tho 60 volts is alot of back feed.

Unless NEC has changed something, there is no code that says you have to remove it, but locally there may be other codes.

Insulation around the wires, the rubber surrounding the soldier joints, and the insulation around the wires coming into a box (drying out) are normally the biggest faults of K&B, tho they are more

I am curious as to what the electrician said/did, and what suggestions he had being that they are in a different state than me
 
Lots of insurance companies would drop you like a hot potato for having knob and tube. I doubt any mortgage company would loan money on your house.

It was good when new, but the insulation gets old and cracks and during building settelment, the tubes can crack.

Its time to fix it right.
 
blazer58 said:
Dirk,
I hear what your saying, thus reason I pointed out, when we come across it here, they make us remove it.
I assumed when trivetman said he capped the wires and left them, they were in a/the switch box.

He did say he was calling an electrician, so I did not get into the voltage drop.
Knob and tube, many times the neutral was switched, not the hot leg, there could be back feed on the neutral side,
tho 60 volts is alot of back feed.

Unless NEC has changed something, there is no code that says you have to remove it, but locally there may be other codes.

Insulation around the wires, the rubber surrounding the soldier joints, and the insulation around the wires coming into a box (drying out) are normally the biggest faults of K&B, tho they are more

I am curious as to what the electrician said/did, and what suggestions he had being that they are in a different state than me
Click to expand...


Oh, I may have misinterpreted what the OP meant by "This would leave hot K&T in my walls."

Capping the ends in the box was my "part A." If he's done that in the existing box, then that's fine.

But "part B" was about properly troubleshooting the original problem. For the place in which my family sleeps... I couldn't let that go... He's been granted an indication of a potentially serious problem with no consequences so far. I'm just suggesting he accept that gift!
 

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WHOA Dirk -

Not sure what I wrote that made you think I was going to cap the wires with bubble gum and cover them in plaster. “I’m calling an electrician” could have been an indication that I am trying not to do something dangerous. I know you’re just trying to shout loud to keep me from doing something stupid.

yes - capped wires would be in junction boxes if we take that route. Electrician will be here tomorrow. I know that there is nothing mandatory in this area about ripping out K&T. I’ll keep you posted.
 
"cap the wires with bubble gum and cover them in plaster"

I have come across that a few times, tho they were just wrapped in cloth tape in and then buried in the plaster. It really amazes me what some people do with electricity.
When I read you were calling in an electrician I figured you would not be doing anything unsafe
Keep us updated, I really would like to know what he has to say. He might even have an easy fix to get rid of it without destroying all of your walls/ceilings
 
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Dirk said:
But "part B" was about properly troubleshooting the original problem. For the place in which my family sleeps... I couldn't let that go... He's been granted an indication of a potentially serious problem with no consequences so far. I'm just suggesting he accept that gift!
Click to expand...

No doubt about it...but I’m also not going to underestimate what its going to take to modernize. Moving a switch box involves a little plaster patch and paint. Getting out this network of K&T would mean significant digging through the walls of three or four rooms and if you’re digging through a wall...better take care of everything else in that room too. Yes - that means these rooms move up on the priority list and it’s realistic in my case to probably do it within a couple of years But no...its not a job for a couple of weekends.
 
I know you’re just trying to shout loud to keep me from doing something stupid.
Click to expand...

Ha, well, I might have been projecting. We've all been tempted a time or two to take a shortcut! Or gotten stung by what we don't know we don't know!

You did say you were going to "call an electrician" but you also wrote like you were doing this work yourself. So it wasn't clear if you were literally just going to call one on the phone, or what you might ask of him, or if you were going to actually hire one to do the work and troubleshoot the problem.

I'm not nit-picking, I'm always nervous about reading or advising in electrical threads. There's no way to know for sure what a person's experience or intentions are... So I tend to over compensate...

I'm glad to hear you're being thorough.
 
Update for those interested.

Electrician came out. Looks like the original problem was related to the fixture, not to internal wiring. The voltage drop I saw was tested at the switched neutral and so was affected by the bad fixture. Internal wires are old but functional. He extended the wires with a couple pigtails so I wouldn’t be moving the existing wiring around when I put a fixture up.

Its an old area (Philadelphia suburbs) and I think K&T that hasn’t been ripped out is still pretty common. When people “redo” the electrical its often not a complete job - but only really re-doing what isn’t concealed - I would guess for house sale. As long as electricians around here don’t see any immediate problems with it they tell you it’ll be ok and be on their way.

I’ve replaced quite a few switches and outlets in my house over the last year and this is the first sign of K&T I’ve seen. Who knows if it’ll be the last. I’ll get it replaced down the road, but it’ll be a bit before it happens.
 
Excellent news! Whew. Walls intact! Yay!! ;)

As blazer58 pointed out, there's nothing particularly wrong with knob and tube, or dangerous about it. Plenty of it still around, working great.
 
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