question about replacing knob and tube

ocelli77 · 11-23-2012, 10:25 PM

Bought an older home that has some knob and tube in one circuit. From panel to kitchen, it has all been redone. But some lights upstairs and in attic are knob and tube. I am hiring an electrician to replace all knob and tube.

I wonder if the kitchen wiring can be saved and disconnected from the knob and tube by terminating the line after the last Romex-wired fixture. No idea where in the wall it is sliced to Romex but know where the fixtures attached to knob and tube are. To preserve the kitchen wiring (lots of lights, three way switches, etc), will the following approach help identify where the splice is: open each fixture on Romex and disconnect the outgoing wires one fixture at a time to find the wires that continue to the knob and tube. If the circuit were temporarily terminated at each kitchen fixture (with the line supplying the knob and tube was disconnected), then the power would be cut to the remainder of the knob and tube fixtures, showing that the splice is upstream of the place where the disconnect occurred. Once identified, the knob and tube could be permanently disconnected from a power source.

If this works, then one could keep the kitchen circuit and add new circuits to rewire all the remaining knob and tube fixtures.

I would appreciate any insights.

frenchelectrican · 11-23-2012, 11:33 PM

The biggest issue you will snag into what the old T&K were run is the power source it is very common to find the power source at the luminarie junction box ( I know there are few case no junction boxes at all ) and you mention three ways this will get more trickier to deal with it due some of old T&K three way still wired in Carter format ( it been discussed in few thread in the fourm but I will post the diagram so you will get the idea ) and for myself I will not try to attempt to save the exsting circuit due the key issue is ground conductor and with romex cable most older one do not have ground conductor in there so I will not touch them useally they go out of window.

If you have ballon frame house it will be little easier to do this if the wall is not really insulated well you can fish them thru the wall cavity without much effort.

Expect some holes show up a good electrician will keep the holes to bare minuim depending if you do not have hortzonal fire block you are ok with it ( on the wall ) but expect that going to be happend.

Otherwise inside wall is next best choice if you only deal with one floor you will be ok.

But that pretty much up to the electrician call what they think the best route to run the new conductor and see what they think about it.

I will post the cariter three way switch set up look like in case you still have T&K in the switch box.

Expect that if you do have T&K at the switch box this will be a one way you can be prepared for it.

Merci,
Marc

ocelli77 · 11-24-2012, 08:30 AM

Thanks for your answer Marc.

I am not sure that the Cartier wiring was used. From the panel box, there is Romex to the lights and light switches in the kitchen. It seems to be done by code using proper wiring methods. However, in the next room the overhead light is wired with knob and tube, and this fixture is supplied by the same circuit as the kitchen.

To identify with receptacle is connected to the wire that supplies the knob and tube fixture in the next room, could one disconnect the wires leading out of the kitchen lights (or switches) to determine which wire supplies the knob and tube. If a wire is disconnected AND all the kitchen lights are on, then that wire must be the one that supplies the knob and tube. Then one could disconnect the knob and tube wiring permanently and add new circuits to supply the lights in the adjacent room.

Does this work?