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  1. #1
    Join Date
    Sep 2013
    Location
    Connecticut
    Posts
    3

    Default Old Wiring, New Lamp

    Hi,

    I'm new to the site and thought I'd ask a question. I have a 1939 home in CT. I'm installing a new outdoor lamp over the garage and I can't tell which wire is "white" or "black". I guesses and popped a breaker. I'm wondering if I do the opposite would that mean I have it right or does this mean there may be other trouble?

    Appreciate the help. Electrical has never been my strong point.

    Mike

  2. #2
    Join Date
    Jul 2010
    Location
    SoCal
    Posts
    7,344

    Default Re: Old Wiring, New Lamp

    Reverse the wires carefully, should be OK.

  3. #3
    Join Date
    Dec 2012
    Location
    New London County, CT
    Posts
    124

    Default Re: Old Wiring, New Lamp

    I was working on my Dad's house and had the same problem. I made up a long single conductor wire that I could ground and then use that with a voltmeter to test between the two wires. The live wire was then wrapped with colored tape. You may measure some voltage between the ground and the neutral wire and that may be normal.

  4. #4
    Join Date
    Jul 2010
    Location
    SoCal
    Posts
    7,344

    Default Re: Old Wiring, New Lamp

    To avoid such mistakes, such as which wire is the hot and which one is white in the future, mark the wires BEFORE you disconnect them.

    When I work on replacing circuit boards, where I have a dozen wires or more, it's critical to label all wires as you disconnect them.

  5. #5
    Join Date
    May 2008
    Location
    Pacific Northwet
    Posts
    1,794

    Default Re: Old Wiring, New Lamp

    Based on the age of your home and the description of the wires, you likely have old wiring that's insulated with rubber and covered with a cotton overbraid. Over time, this overbraid has discolored with age to the point you can't tell the difference between the wires. If you look carefully, you may see that the cotton overbraid on one wire has a black thread woven through it. This is usually the hot, but not necessarily so: testing as described by condoman is the best way to be sure.

    Chances are the rubber insulation on the wire is brittle. I recommend putting heat shrink tubing over these wires before installing the fixture. Use a heat gun -- not a match or torch -- to safely shrink the tubing.
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

  6. #6
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,941

    Default Re: Old Wiring, New Lamp

    Some detail must be missing in the post, even if you reversed the wires on a new lamp it should not trip the breaker.


    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

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