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RST 11-28-2011 11:45 PM

Lost Neutral on K&T Circuit
Recently bought a foreclosure. Very old two-story house with a variety of wire types. Most knob and tube has been replaced except for a lighting circuit that powers the first floor overhead lights.

The last three switched luminaries on the circuit don't work. For all three fixtures, the hot wires go through the switches and then on to the fixtures. The neutral wire follows an entirely different path to connect the fixtures to each other and the rest of the circuit.

We're replacing carpet in one upstairs room so we ripped up floorboards to access that portion of the circuit. We did some other testing and believe that the neutral is broken somewhere between the first of the three fixtures and the rest of the circuit. This is because all other lights on the circuit do work correctly. Of course, this broken wire is under a good quality floors upstairs that we prefer not to destroy and the downstairs ceiling is a textured plaster and lathe.

Are any of these other options acceptable?
> Connect a neutral wire between one of the non-working fixtures and the neutral bar on the panel.
> Run a neutral wire from one of the non-working fixtures to a working fixture elsewhere on the circuit.
> Run a neutral wire from one of the non-working fixtures to a neutral wire on different circuit (for example, to the nearest receptacle).


Techy 11-29-2011 05:55 AM

K&T is not allowed to be modified, only replaced.

AllanJ 11-29-2011 06:18 AM

Time to rewire the circuits and rooms. You can temporarily mount new outlet boxes on the surface of the wall and run the wires on the surface using such materials as Wiremold to protect the wires (all new hot, neutral, ground).

You may never connect a receptacle or light fixture, etc. powered by one circuit to a neutral that serves a different circuit. Neutral must accompany the corresponding hot all the way back to the panel.

joed 11-29-2011 08:01 AM

Replace it while you have it exposed.

RST 11-29-2011 11:25 AM

Darn, I was afraid you folks would say that.

Is it acceptable to replace the K & T in the non-working portion of the circuit and replace the rest later? I'm not extending the circuit or changing anything else, just replacing wire. Would this be considered an illegal "modification"? I'd have to rip up flooring, bust into walls, or destroy ceilings in 3 additional rooms to replace the whole circuit unless I went with Wiremold.


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