Adding additional light and switches to K&T existing wir

[rodgersj]

I have knob and tube (k&t) to two existing lights (one interior ceiling light and one exterior light fixture). I added two interior canister lights and snaked romex down to the existing plastic box. I had to remove the existing two switch box, and replaced it with a three switch old work plastic box. The problem is now I have three wires coming in (one from the outside light and one from the inside light (k&t coming in)) and one other lead coming in (assuming to be the hot lead) and the romex I snaked in, but cannot successfully light the newly installed canisters. I have tried to just use a single pole standard switch with power for the additional lights coming from an additional power source, as well as coming from the power source for the existing lights. When using a power source for near the lights, then thru the lights down to the switch, they light fine, but when I try to turn off the switch, it throws a breaker, regardless of which additional power source I am using. I need to try and find out why the breaker is getting thrown or what part of the power source I am incorrectly connecting to determine the problem, any imput would be greatly appreciated.

[Wgoodrich]

Knob and tube wiring normally ran the power to the light fixture then only a hot wire and intermittent hot wire from that light fixture to that switch. YOu will most likely not find a grounded leg [aka neutral] wire in that switch box to add a new switch and lights from. You need to run a power source from a receptacle of a light fixture that has both a hot and a grounded leg [aka neutral] wire.

Easiest to lessen confusion is to run a romex cable 12/2wGrnd from a receptacle nearby to take a new power source to that switch box. Then wire this new switch and lighting system separately from the existing switches and lighting.

Just pick up a power source connecting a black wire of the new romex to the brass screw of a nearby receptacle and a white wire connecting to the silver screw of that same receptacle. Then run that new romex to that new switch box. Wire nut the white from the receptacle to the white going to your new light fixtures only. Connect the black wire from the receptacle to one brass screw of your new switch and the black wire going to your new light fixtures to the second brass screw of your new switch. Leaving the old existing switches untouched as they originally were.

Hope this helps

Wg