Knob & Tube question

[mikejurasw]

Hi all, I'm working on a couple older homes ('20s...1920's) and both have K & T wiring. I'm replacing light fixtures, and up in the old junction boxes are the two identical wires (no white or black), but one has an overhand knot it it. I expect this was the old-timer's way of indicating which was which. I'm wondering: is it "knot=hot", or "knot=neut.",?
Follow-up: does it actually matter, for an end-of-the-line fixture like a ceiling light?
Thanks!
MM

 

[Snoonyb]

The knot is probably a local tradesman issue.

However there are simple voltage testers that will tell you which is the hot, similar to this; https://www.newark.com/wiha/25511/i...hopping-NewStructure-Tools-ProductionSupplies

Where it makes a difference is in the switching, IE. if you are switching the neutral there remains a hot conductor connected to the fixture.

 

[bud16415]

I'm sure in your case one is hot and one the neutral and as described above test for voltage at the switch and switch the hot.

The thing is with K&T they didn't always run the hot and neutral as a pair like we do with modern wire that comes bundled together in the same sheath. I have seen the neutral come from one direction and the hot the other or two wires together and they are both hots with no neutral as they pick it up someplace else.

A lot of these were done like plumbing where the water supply and the drain line are two different paths.

Proper K&T joints are twisted and soldered then a rubber tape and then cloth tape. They were a really safe thing in their day. Just that a 100 plus years will wear anything out even the copper gets brittle and the insulation turns to dust.

 

[user 4883]

"end of line" really doesn't change anything. You don't want to mix the hot and neutral on a fixture. 90% of my electrical work has to be done hot so I take precautionary measures at all times but, you typical homeowner won't bother with that when simply changing a lightbulb.
Chances are you don't have anything ground at the fixture to check hot from neutral.
I would employ the use of a NCVD (Non contact Voltage Detector) to find the hot, just make sure the leads are clear of everything to avoid a short or shock.

 

[geochurchi]

Hi, also make sure that the neutral is connected to the screw shell of the fixture.
Geo

 

[Eddie_T]

I have an Ne2 tester that is my go-to in my tool box. It is much easier to grab than a meter for house circuit resting.

 

[mikejurasw]

Thanks, everyone! I really appreciate the input; I'm trying to learn as much as I can and this has been a great forum. Following up on the question of safety in K & T wiring; as long as I'm in the boxes and walls, would it be worth it to fish a new Romex line and cap it, but have it in place for a real electrician to hook up? I mean, over the years I've probably had access to 50% of the outlets and circuits...
MM

 

[user 4883]

I can see the temptation to pull new wires but, an Electrician may have reservations about using your runs versus running his own to make sure everything is Ok. Maybe run some fish strings from box to fixture so he can use those and might give you a break on the price.
Oh, almost forgot, let us know if that knotted wired happens to be the Hot.

 

[mikejurasw]

will do! Thnx all...
MM