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CoconutPete 01-07-2013 08:04 AM

Small single copper wire found running on various joists. What is this?
I've noticed this on a couple of different joists in my unfinished basement. At first I flat out thought it was just a piece of twine that was clamped to the joists, but yesterday I noticed what is apparently the insulation broken in one spot exposing a single copper wire. These look as old as the house (1930).

I can't really seem to track them to a destination but I did find 2 of them running through a hole in the rim joist to the outside, but there is no corresponding hole in the siding outside.

Any idea what this is / was for?

rossfingal 01-07-2013 08:06 AM

A potential, fire hazard?!?
Are they live?


CoconutPete 01-07-2013 08:09 AM

Well it certainly doesn't carry high voltage, I honestly forgot to test for low.

The wire is very thin BTW, think ipod headphones after it has split into L/R and imagine just one of the sides - that's how thin it is.

joecaption 01-07-2013 09:14 AM

Sounds like door bell wiring.

md2lgyk 01-07-2013 10:27 AM


Originally Posted by joecaption (Post 1088178)
Sounds like door bell wiring.

Or someone's long ago attempt to add a ground to ungrounded outlets. The ground wire used to be much thinner than the other two conductors.

joed 01-07-2013 10:38 AM

Sounds like door bell wiring to me also. Can you post a picture of the wire and anything it might be connected to. Might be telephone as well.

SuperJETT 01-07-2013 10:53 AM

What size are you walking about, very thin? Like the others mentioned, probably doorbell wiring. One of our previous houses was built around 1907 and was originally a 700sq ft shotgun but was 1800sq ft when we lived there. It had been changed tons, including where the outside doors were, so there was old doorbell wiring, etc etc throughout the place.

Wildie 01-07-2013 11:39 AM

I had a house that was built in 1911 and it had a single wire running outside and it terminated on a porcelain terminal block. Originally, an outside antenna was connected to it.
At one time the other end went to the family radio. Radio's at that time were usually tri-band tuners. Short wave, broadcast and long wave!

CoconutPete 01-07-2013 12:23 PM

I don't think it's telephone. I have found 2 diff. types of telephone wires in the house. The "modern" one which was obviously added after the fact and the older 3-wire style with the metal junction boxes - it doesn't look like any of those.

There is a doorbell transformer still present - it looks old, I honestly have no clue when it's from, but both it and the doorbell work fine and this wire in question is not near either of them.

It's not near any electrical boxes, so I don't think it's a grounding attempt either.

The radio thing sounds interesting.

I'll get some pictures later.

joed 01-07-2013 02:34 PM

I missed that it was a single wire. Either an antenna or a piece of knob and tube electrical wiring. Do you have a non contact voltage tester to see if it is live?

CoconutPete 01-07-2013 09:20 PM

3 Attachment(s)

Missouri Bound 01-07-2013 09:32 PM

Old telephone grounding wire? :eek:

Wildie 01-07-2013 09:55 PM


Originally Posted by Missouri Bound (Post 1088701)
Old telephone grounding wire? :eek:

I agree! The tip off is the cable mounting loops! Standard issue for phone wiring!

chrisn 01-08-2013 03:01 AM


Originally Posted by Wildie;1088723[COLOR=red
]I agree[/COLOR]! The tip off is the cable mounting loops! Standard issue for phone wiring!

me too,I have the same in this house

CoconutPete 01-08-2013 08:12 AM

So by "old" telephone grounding wire, you mean they went along with the old 3-wire phone lines with the metal junction boxes which were replaced with the 4-wire ones later on right?

At a later time I want to move a duct on the other side of the basement, one of these things is in the way. It sounds like it would be OK to just chop this?

Where do you think the 2 that run through that hole in the rim joist go anyway?

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