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Dterron
Knob-and-tube wiring

Four years ago we purchased a home built on 1925. Much of the home has knob-and-tube wiring. Beautiful older home. Here is the problem. In the living room we have a nine foot ceiling (plaster and lathe). We want to install a ceiling fan. There exists an electrical box that was capped where there used to be a ceiling light. The previous owner said they could not get a light to operate. I called an electrician to ID the problem. He said it appears there is no ground. He suggested to cut out a section of plaster and lathe to look for broken ground. Did that and and found no break. Appears this is the only area not working in this circuit. Could wire be too old or brittle? What else should I look for? Any to test? Need advise.

Blue RidgeParkway
Re: Knob-and-tube wiring

i never heard of K&T with ground. a grounded wire and a hot wire yes but not a grounding wire. what you say your "electrician" says doesnt make sense.

what makes more sense is a switch somewhere wired wrong to open the grounded wire not the hot or abandonded switch wiring in wall that was wired wrong originally or a broken or unsoldered grounded wire and someone left a live hot in the box.

i wouldnt but a ceiling fan on 80 years K&T. for sure youd need a different ceiling box that was supported better and deeper anyway. consider upgrading the wiring?

Dterron
Re: Knob-and-tube wiring

Sorry for explaining so poorly. I meant to say grounded wire. Originally the two wires came down thru two holes from plaster and lathe ceiling. What you have said makes sense. I tried switching wires in switch and still nothing. Next, I tried the following. Using a lampholder and bulb as the tester, I connected the black wires and the white wires resulting in no light. Next, I connected the blackwires and then connected the white wire to the neutral side of a drop cord I had plugged into a nearby outlet. Bingo-I had a lighted bulb(dimly lighted). Where is the problem? How can I fix this?

JLMCDANIEL
Re: Knob-and-tube wiring

As mentioned above you may have to replace the ceiling box with one rated for the weight and vibration of the fan. The only thing you can do is trace the wire back until you find a good connection. Personally rather than repair I would replace and update the service at the same time. If the service and wiring had been updated it may be that the K&T wires were just disconnected and left in place. in that case you don not want to reconnect them.
Jack

libcarp
Re: Knob-and-tube wiring

It's a rather poor electrician that has to cut out a section of plaster and lathe to go looking for broken wire - a continuity test is all that is required and can be done in less than a minute. They can even send an RF signal through the wire to determine exactly where the break is at.

Dterron
Re: Knob-and-tube wiring

Libcarp, thanks for your input. What type of equipment do I need to send an RF signal through a wire to locate a break in the wire?

Blue RidgeParkway
Re: Knob-and-tube wiring
Dterron wrote:

Sorry for explaining so poorly. I meant to say grounded wire. Originally the two wires came down thru two holes from plaster and lathe ceiling. What you have said makes sense. I tried switching wires in switch and still nothing. Next, I tried the following. Using a lampholder and bulb as the tester, I connected the black wires and the white wires resulting in no light. Next, I connected the blackwires and then connected the white wire to the neutral side of a drop cord I had plugged into a nearby outlet. Bingo-I had a lighted bulb(dimly lighted). Where is the problem? How can I fix this?

you are saying you did this? oh my GOD! you need to STOP right now before you shock yourself, electrocute yourself or burn your house down. A direct short should have blown your fuse or tripped your circuit breaker if you even have that. of course no protection if you have a penny where a fuse should be. if you still have old fuse box you might even have fused neutrals.

advice: hire a qualified electrician who has testing equipment and knows how to use it and stop doing what you are doing.

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