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  1. #1
    Join Date
    Mar 2009
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    Charlottesville, Va.
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    292

    Default What type of conductors are these

    I need some help identifying these conductors please.

    At first they look like aluminum, although I have minimal experience looking at aluminum wires, but if you look closely at the first photo and close up in the last photo you can see a tiny abraded area that appears to show a copper core.

    The house is a 1935 house and I assume these armor clad conductors are original which would not be consistent with what I know about aluminum. I think I remember some type of copper cored conductors but can't remember the details.

    Thanks.

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  2. #2
    Join Date
    Mar 2009
    Location
    Colorado Front Range
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    601

    Default Re: What type of conductors are these

    The wire is tinned copper. The insulation is rubber based and copper sets up a reaction with the rubber so it is tinned (essentially solder coated) to help prevent the copper and rubber from coming in contact.

    As a side note, a lot of this old rubber insulation has turned to powder held together only by the fabric covering.

    I've climbed into dark attics where the old rubber coated wire is in a spiral metal sheath (type BX cable, and present here) and been able to observe a dull red glow where the sheath is carrying current because of insulation failure. BX is definitely something that requires a close inspection if present.


  3. #3
    Roger Frazee's Avatar
    Roger Frazee Guest

    Default Re: What type of conductors are these

    From what I see in the photos that BX has come real close to seeing its day....

    If any or all of those 3 circuits served by the BX have light fixtures in the circuit you will likely find just what Bill explained .... complete deterioration of the insultation into powder. I've opened many incandescent lighting fixtures where the rubberized insulation (cloth covered) simply falls off the conductor when you take the wirenuts off ...if wirenuts are even present .. this of course leaving you with bare conductors. The heat from the bulbs is just to much for that type of insulation over time. And of course too high wattage bulbs installed by the homeowners speeds up the process. Couple that with the conductor heat generated from current flow and you will get failed insulation on that type of wiring sooner than you might expect.


  4. #4
    Join Date
    Mar 2007
    Location
    Ormond Beach, Florida
    Posts
    26,252

    Default Re: What type of conductors are these

    Quote Originally Posted by Roger Frazee View Post
    The heat from the bulbs is just to much for that type of insulation over time.
    The rubber dries out even when not near lamps, even in the device boxes, and in the panels - the NEC warns of rubber insulation deteriorating (as I recall, I have looked recently to see if it is still in the NEC with that warning).

    If you have rubber insulated conductors, the house more-than-likely needs to be re-wired.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  5. #5
    Roger Frazee's Avatar
    Roger Frazee Guest

    Default Re: What type of conductors are these

    Yeah that's true, seems I remember way back in a class discussion several years ago that exposure to oxygen played a big role in making the rubber brittle. So anywhere terminations were made the insulation was more prone to completely fail.

    We have a lot of the stuff in our homes around here that were built during the WPA post WWII era.You pretty much could figure on replacing the wiring all the way back to the originating panel. The heck of it was they spidered out from these ceiling juction boxes and if you messed with them the problem just escalated

    Often times the wires were soldered in these jbs and seems I remember that they always tinned the copper if rubber insulation was used for the conductors. I believe Bill touched on the why of it. My little history file shows 1922 or close for when they first started using rubber insulation on interior house wiring.

    Last edited by Roger Frazee; 07-19-2011 at 09:32 PM.

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