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Thread: Knob and tube wire

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    Knob and tube wire

    I have never dealt with old knob and tube wire before. Have a chance to get some along with a bunch of copper plumbing pipes from a home reno. I will be purchasing the scrap.



    I'm assuming knob and tube wire will be copper? Will it be #1 or #2 or something else all together? Just want to be able to give the guy an accurate quote before I go to meet him.

    Edit- Just want to add I did search the forum and came up empty


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    tackleberry, I would think #2 copper. I picked some up during a reno job this past summer. It was heavily oxidized and splices are soldered together. Actually, it's still in my garage somewhere. I'm not sure what to do with it since I hear that some of the insulation may contain asbestos.

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    Quote Originally Posted by Otto View Post
    tackleberry, I would think #2 copper. I picked some up during a reno job this past summer. It was heavily oxidized and splices are soldered together. Actually, it's still in my garage somewhere. I'm not sure what to do with it since I hear that some of the insulation may contain asbestos.
    Oh yikes. Much appreciated info Otto.

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    Will be #1. But it is much harder to strip as it is typically surrounded by a asphalt saturated fabric loom. u can burn it wich makes the loom brittle and it can then be taken off with your fingers. some of the wire may be bare already.

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    Quote Originally Posted by Otto View Post
    I'm not sure what to do with it since I hear that some of the insulation may contain asbestos.
    im pretty sure its just cotton. If someone knows for sure let us know.

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    I will look into it a little more, he is in the process of gutting the house now so I have a bit of time. I certainly won't be taking any chances.

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    Wikipedia Article

    It says that early knob and tube wire used asphalt soaked cotton fiber, but I wouldn't rule out the possibility that other materials could have be used by different manufacturers.

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    I just read somewhere that some older houses were wired with AL.....be sure it's CU....

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    Knob and tube wire can have asbestos in it it. It will usually be white or brown. I have taken it to the yard as is and had no problem. Asbestos is only dangerous if it can be made into a dust which is then breathed in. Just take it in as is b/c I personally wouldn't chance it ever. The first time I got the stuff I stripped it and then burned the white fibers...except it didn't burn..... only then did I realized it was asbestos and have never stripped them again.
    Determine never to be idle. No person will have occasion to complain of the want of time who never loses any. It is wonderful how much may be done if we are always doing.
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    Thanks for the info Hypoman.

    And thanks Dee, always good policy to never assume and check material to make sure you know what you're getting. Can be easy to get caught up in the excitement of a deal only to find out later you should have been a little more careful.

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    All knob and tube I have had anything to do with was copper and yes the joints were soldered. I don't know if you can solder aluminum, I doubt it. Aluminum house wiring came in much later and was then banned because of the number of fires that started due to poor connections.

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    Just thought id clear this up for all of you. I am an electrician with 20 plus years experience dealing with old houses. Most knob and tube wiring is actually tin coated copper in cloth, asphault, or burlap thread. It does not and never has had asbestos in it or on it. if you took the time to strip a small portion of it, you would see the coper core, but the silver exterior. good luck!

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    I would base your price on on getting paid for #2 and cash in as is. If you get #1 price, great, but cover yourself just in case. I tend to strip things most people wouldn't bother with and even I think it isn't worth the battle to strip. Good luck!
    Satisfaction is the death of desire.

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    What a really scarey way to wire a house up....
    Knob and tube wiring - Wikipedia, the free encyclopedia

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    ^ Wow, someone did a beautiful job of cleaning up the lath and plaster in the top photo. Nothing like the s*** holes I usually encounter.

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    Quote Originally Posted by rmcgovern22 View Post
    Just thought id clear this up for all of you. I am an electrician with 20 plus years experience dealing with old houses. Most knob and tube wiring is actually tin coated copper in cloth, asphault, or burlap thread. It does not and never has had asbestos in it or on it. if you took the time to strip a small portion of it, you would see the coper core, but the silver exterior. good luck!
    I am sorry my friend, but you're wrong. It was used as an insulation.


    Problems Associated with K&T Wiring:

    Unsafe modifications are far more common with K&T wiring than they are with Romex and other modern wiring systems. Part of the reason for this is that K&T is so old that more opportunity has existed for improper modifications.
    The insulation that envelopes the wiring is a fire hazard.
    It tends to stretch and sag over time.
    It lacks a grounding conductor. Grounding conductors reduce the chance of electrical fire and damage to sensitive equipment.
    In older systems, wiring is insulated with varnish and fiber materials that are susceptible to deterioration.
    Compared with modern wiring insulation, K&T wiring is less resistant to damage. K&T wiring insulated with cambric and asbestos is not rated for moisture exposure. Older systems contained insulation with additives that may oxidize copper wire. Bending the wires may cause insulation to crack and peel away.



    From Knob-and-Tube Wiring - InterNACHI Knob-and-Tube Wiring - InterNACHI



    Safety

    Knob and tube wiring used cloth insulation. Over time this insulation can wear out, become brittle, and fall off, leaving bare wire. The ceramic knobs and tubes provide some protection because even if the insulation does fall off, the bare wire can not touch the wooden structure. The insulation is also somewhat flammable. Some knob and tube insulation contained asbestos, which can cause cancer. Unlike modern wiring, splices were not contained in a protective box. If a splice failed, it could make a spark and start a fire. The fuse boxes usually had no protection from using an incorrect fuse. An incorrect fuse could cause the wiring to overheat and become damaged or start a fire. Another problem is that when a fuse blew, people who didn't know or didn't care about the hazards would sometimes replace it with a coin or a ball of foil if a replacement fuse wasn't available, leaving no overload protection at all. These issues can be partially corrected by installing a modern circuit breaker panel with arc fault circuit interrupter breakers. There was also no ground wire. Knob and tube can be updated with a GFCI to add the equivalent of grounding.
    [change]

    Knob and tube wiring - Simple English Wikipedia, the free encyclopedia



    Then on the EPA website on page 18 of document under the heading "Electrical Equipment"

    Document Display | NSCEP | US EPA

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    I looked into knob & tube wiring insulation containing asbestos a while ago. From what I can recall, it was only required in places like theaters and not residential applications. It makes sense because it would have been more expensive than the standard non-asbestos containing version. If I come across it, I just burn a small (2 - 3 inch) section to see if there is any white asbestos fiber left with the ash. So far, I haven't come across any containing asbestos, but I don't deal with it every day.

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    Quote Originally Posted by Otto View Post
    I looked into knob & tube wiring insulation containing asbestos a while ago. From what I can recall, it was only required in places like theaters and not residential applications. It makes sense because it would have been more expensive than the standard non-asbestos containing version. If I come across it, I just burn a small (2 - 3 inch) section to see if there is any white asbestos fiber left with the ash. So far, I haven't come across any containing asbestos, but I don't deal with it every day.

    I once pulled out the old knob and tube wiring from a house built in the early 40's. It had asbestos for insulation. I stripped it and then tried to burn it. Asbestos does not burn, this did not burn. Called my best friend (journeyman electrician....residential.... for 12 years) and asked him about it. He said it was asbestos and that they used in those old houses and it shouldn't be stripped. Just take it in as is. Don't know what else to say about it.



    They who can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety.
    Benjamin Franklin

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    Thanks for that Hypoman. Confirms my caution in testing it first before stripping it. It's messy stuff to deal with though. I haven't come across a lot of it so far (a few scraps here and there). If I did get a larger amount, I'm not sure if I would bother stripping it because of the mess.


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