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Discussion Starter · #1 ·
Hi folks,

this is my first post. Here it goes:
We have a 1914 house. I'm redoing our bathroom. I know we have a few pieces of knob and tube left - overhead lights on the main floor only. The bathroom is on the main floor. I removed lath & plaster. There are two wires going to the switch, no problem, one must be hot, the other neutral. BUT, when I followed the wires to the attic, it turns out one wire, hot, is going into the ceiling and eventually to the breaker box (I figure) but the other goes straight to the light fixture. So I end up with a single, hot wire, in the light fixture box.

I know, I have to run a new circuit from the breaker box sooner than later, but for now (we need our bathroom back), how do I wire the switch/fixture with ROMEX?

Thank you.
 

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Oh, I see, you are missing a neutral to complete the circuit.

AFAIK It's not legal to splice romex to knob & tube. You'd have to run a new circuit of romex to the panel.

So, follow your local building codes and consult the professionals, and install a new cable. I'd suggest bringing power to the switch. So, Breaker panel > Switch > Light.


I know, I have to run a new circuit from the breaker box sooner than later, but for now (we need our bathroom back), how do I wire the switch/fixture with ROMEX?
Unfortunately you'd need to do that now (if you want to be legal).
 

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Discussion Starter · #12 ·
Thank you for looking at this ... I will run a new cable asap. My understanding of the local code is I'm able to extend K&T with ROMEX as long as the connection is done within a box. I will not add any additional load.
 

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With knob and tube, sometimes the neutral follows a completely different route back to the panel e.g. hot goes up the front of the house and neutral comes down the back of the house.

So you can very well have the hot routed from breaker panel to the switch and on to the light with no neutral in the switch box, as shown in the diagram above.

As I understood it, K&T may be decommissioned and replaced with Romex or other modern wiring piecemeal. But an orphaned section of K&T may not be re-energized by a different K&T branch circuit.

For the diagram above, run the Romex starting from the left (panel not shown at far left). When you get to the light fixture, you're done.

Cap off any unused K&T conductor including the single wire neutral in the light box and curl them up inside the boxes until you are sure that all other ends including conductors branched or teed to them have also been disconnected.
 

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To properly abandon K&T cut the wire a bit past a knob and wrap the wire back around the knob and then around the taught wire. Tape the end up. An inspector might want it soldered and taped but I've never been called on it.
 
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