knob & tube single pole conversion to dimmer


Old 12-17-05, 02:17 PM
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knob & tube single pole conversion to dimmer

I'm replacing a single pole light switch in a 1920's house with a dimmer. The box has 2 knob & tube wires coming out of it. I tested both and neither is hot by itself, only when the tester is touching both wires at the same time. Neither of the wires is color-coded. The dimmer switch i bought has 3 wires coming out of it. 1 black exiting the bottom by itself and one green and one black exiting out the top of the switch. I assume that the lone black is the hot and may be connected to either of the knob & tube leads. i'm confused about what to do with the other knob & tube lead and the black and green wires from the switch. Can I just attach the dimmer's green wire to the other k&t lead and cap-off the dimmer's 2nd black wire, or do I twist the dimmer's green and black together, then connect them both to the 2nd k&t lead?
Also, the k&t leads have closed circle copper ends on them for sticking a screw through and screwing into the old switch. When connecting my new dimmer's wires to these k&t leads, can I just thread/twist them together and electrical tape the heck out of them? I won't be able to twist any plastic protector cap onto the copper rings. Thanks in advance, Bob.
Old 12-17-05, 10:50 PM
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First things first. Check to see if the dimmer can even be used with this low temperature rated insulation. Most likely it can't be used with K&T. Even without a warning it would be a poor idea to install the dimmmer due to the heat build up that will cook any remaining life out of the K&T. This can cause the insulation to fall off creating a dangerous situation.

Since your wiring method does not contain a ground the green wire would not be used.

NO, you cannot just twist and tape the heck out of the splices. You must use twist-on wire caps AKA wire nuts to secure the splices.

Last edited by pcboss; 12-17-05 at 11:11 PM.
Old 12-18-05, 01:51 PM
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The green is ground. It connectes to neither of the wires there, just to the box or gound wire there, if you have it.
Connect each black wire frome the switch to each wire the old switch used to connect to. It doesn't matter which, really.

You can pinch the wire loop together enough to use a wire cap.

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