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  1. #1
    Join Date
    Dec 2007
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    Holladay, UT
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    565

    Default Tinned copper or aluminum

    I found this wire at inspection today. I am assuming it is tinned copper because of the date of house (1945) and the insulation. I could not see an end of wire to verify. These were the only three circuits in house that had this wire. How can you differentiate (visually) between tinned copper and aluminum when you are not sure?

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    Tom Rees / A Closer Look Home Inspection / Salt Lake City, Utah

  2. #2
    Join Date
    Mar 2007
    Location
    Spring City/Surrounding Philadelphia area
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    3,473

    Default Re: Tinned copper or aluminum

    Tom, what I try and look at is the snipped end of the conductor. If it is tin-clad copper (as I call it), you should see copper. The cut on the end of the wire should form a point and give you a good cross sectional view of the wire makeup.

    From my experience, the cloth braid insulation cover like the wires in your picture indicate tin-clad copper and single strand aluminum wiring has a rubber/plastic insulation cover. Also, if installed properly, aluminum wires need to be sized one gauge higher than what you would use if the wires were copper and are visibly thicker. Therefore, a 15 amp breaker would need to be wired with 12 gauge Al wire as opposed to 14 gauge Cu.


  3. #3
    Join Date
    Mar 2007
    Location
    Oregon
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    2,365

    Default Re: Tinned copper or aluminum

    If you look very close you'll pretty much always be able to see a knick in the tin coating and the copper showing through. And, of course, the cut end is a great place too.


  4. #4
    Join Date
    Dec 2007
    Location
    Holladay, UT
    Posts
    565

    Default Re: Tinned copper or aluminum

    A.D. I take it you mean that the tinned copper is more of a matte finish and the aluminum shinier?

    Tom Rees / A Closer Look Home Inspection / Salt Lake City, Utah

  5. #5
    Join Date
    Mar 2007
    Location
    Washington State
    Posts
    579

    Default Re: Tinned copper or aluminum

    You can pretty much tell if it's tinned copper when it's old cloth sheathed wiring like in the photo. Majority of branch circuit aluminum wiring is from the 70's and is plastic sheathed. When I'm not sure I turn the breaker off and pull the wire out to look at the cut end. However I don't recommend doing this if you don't know what your doing.


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