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What type of wire is this?


Mark P

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A few questions for the more experienced electrician/inspector. Basically I just want to know whatever I can about this wire, its sheathing, rating, etc. In the attached photo, the 3rd and 4th wires down appeared to be aluminum. However the 4th one (with red covering) has a few nicks on it that are copper in color. Why are the nicks that color? It makes me think it is copper on the inside…? The house was built around 1930, the panel was rated at 100AMP, and the main breaker was 70 amps. Thanks for the help.

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Originally posted by AHIS

A few questions for the more experienced electrician/inspector. Basically I just want to know whatever I can about this wire, its sheathing, rating, etc. In the attached photo, the 3rd and 4th wires down appeared to be aluminum. However the 4th one (with red covering) has a few nicks on it that are copper in color. Why are the nicks that color? It makes me think it is copper on the inside…? The house was built around 1930, the panel was rated at 100AMP, and the main breaker was 70 amps. Thanks for the help.

It's coated copper wire. I always thought it was tin rather than nickel, but I don't really know.

It was necessary back then because the wires were insulated with rubber. Without the plating, the copper would react with the rubber.

I think you'll find that all old rubber-insulated copper wire has this grayish metal coating.

- Jim Katen, Oregon

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Yeah,

I call it tin-coated copper wiring. Real common here on houses up to the 60's. I suppose it might be nickel but I think the term tin-coated comes from the fact that one is coating or 'tinning' the wires with an exterior coating. I've never seen a corrosion problem with it.

ONE TEAM - ONE FIGHT!!!

Mike

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Again, if memory serves, I believe the wires you see in the picture would end up in a sheathing that looks somewhat like the material that was used for the webbing in back yard or beach folding chairs, but it probably isn't nylon. Typically earth tone gold and red. This would most likely be the wiring to an old oven, cook top, dryer, etc.

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Originally posted by StevenT

Does the "canvas" cover the entire wire, or is it just at the ends for color coding? Sort of like friction tape?

The cloth covers the wire for its entire length. They were part of a cable assembly as mgbinspect explained. It was manufactured that way, not applied in the field.

- Jim Katen, Oregon

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It is cloth covered for abrasion protection. It is cotton, treated to help with the normal deterioration of rubber. Wire was not bonded to rubber sheath, so could expand and contrat with temp and also deteriorate with exposure to light, etc. I don't think it was nickle plate, as it could be and was soldered in some applications. As Mike referred, "tin the wire prior to fastening". Also, remember this was in the days of friction tape, not plastic electrical tape.

As I remember it, there was a time when rubber tape applied to splice then covered with friction tape. Rubber tape would get really soft and messy and the cloth friction tape covered the glob. I can remember an old electrician using plastic tape for the first time and predicting the end of the world.

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