What are old green & yellow wires in 1917 house?

Reply Mon 29 Apr, 2013 09:44 am
I recently completely removed the original lath & plaster ceiling (and two lower ceilings) in my kitchen. The house is in New England and was built in 1917 with knob & tube wiring. I exposed a network of thin string-wrapped copper wires. These wires were put in when the house was built. The wires are about 1.1 mm in thickness and have white string wound around them one way and colored string wrapped around them the other way. There are both yellow and green wires, and their networks roughly overlap. (There are places where I can only see yellow crossing.) Where two wires are connected and where there is a Y in the line the copper is left exposed. The wires run around (touch) joists. A simple non-contact voltage tester indicates that voltage is present in these wires. All of my googling turned up nothing about these wires. Because European grounding wires are wrapped in a green and yellow sheath, I assume that these wires are be grounding wires.
I plan on calling an electrician, but wanted to educate myself about these wires beforehand. Thanks!
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Reply Mon 29 Apr, 2013 09:48 am
I also own a home in New England, but mine is older. I don't think we had those wires (ours was built in 1897) but that's not necessarily dispositive.

With the grounding, is it possible that this is more or less a lightning rod?

I leave this to the better-skilled than I to answer it, but you've piqued my curiosity as well.
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Reply Mon 29 Apr, 2013 12:17 pm
Phone wires are green, red, black and yellow. Green and red make up line one.
Reply Mon 29 Apr, 2013 01:20 pm
I agree they are likely phone lines but may have been put in before the color standardization. I think a phone line on the hook and not ringing has a 48VDC potential across it so if you get that on your voltmeter you probably have your answer.
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Reply Thu 2 May, 2013 09:26 am
They were door bell wires! I think that they carry between 10 and 16 volts. (I found a transformer in a dark and dusty corner of the basement.)
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Reply Mon 23 Sep, 2013 02:45 am
okay, based on your info it appears that these are grounding wires. Get in touch with an electrician at the earliest.
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