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  1. #1
    Join Date
    Oct 2014
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    Maryland, DC, and Northern Virginia, electrical only
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    444

    Default 1950s residential wiring . . . and 1950s residential wiring

    Two DC-metro brick houses in nice neighborhoods wired in the mid-1950s: one rag, one thermoplastic. Went thought the rag house today, and it easily could have been wired in the 1940s or 1930s: few circuits, brittle wiring. The thermoplastic-wired house's electrical insulation was fine, though of course not rated for use with most of today's luminaires.

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  2. #2
    Join Date
    Mar 2007
    Location
    Fletcher, NC
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    28,032

    Default Re: 1950s residential wiring . . . and 1950s residential wiring

    Did the cloth covered NM cable have rubber insulation or thermoplastic insulation on the conductors?

    "Brittle" indicates that it had rubber insulation on the conductors. I have not seen any rubber insulated conductors where the rubber insulation was still visibly good, much less it being likely to have any chance of having decent insulating qualities.

    Jerry Peck
    Construction/Litigation/Code Consultant - Retired
    www.AskCodeMan.com

  3. #3
    Join Date
    Oct 2014
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    Default Re: 1950s residential wiring . . . and 1950s residential wiring

    Clarification: it was AC cable with rubber-and-cloth-insulated tinned wires.

    And yes, most of that is brittle. I have found some that was yet flexible. Of course, how flexible is another matter. Today's was an aging-in-place situation, not up for rewiring, so . . . is the rubber still insulation? I probably could measure a good insulation reading if I wanted. At the right spot. Mainly, though, it's a spacer; that is, if it's untouched, unvibrated, left in place. And at 120VAC, I am good with >1/8 spacing.

    I do encourage AF/GF protection, given that the helical armor is something of a choke and the spacers around the wires --see? I didn't call them insulation--are iffy. I pulled out a switch today, glanced at the conductors, taped the device before putting back in, restored power and popped a fuse. When I checked, I saw that the cloth bit over one tinned conductor was masking the fact that it had lost its rubber. More tape.

    A house like this, I'd replace the wiring devices and probably it would last out the life of the occupant. However, each time a device is replaced the process stresses that rubber, so it takes a lot of care. With enough room in the boxes to avoid compressing the old wires, I'd often pigtail to the devices. There have been cases, of course, where you open an enclosure, you have to leave that circuit off for good. Rewiring is needed now.


  4. #4
    Join Date
    Mar 2007
    Location
    Fletcher, NC
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    Default Re: 1950s residential wiring . . . and 1950s residential wiring

    Your description sounds like it is a case for "Rewiring is needed now."

    Jerry Peck
    Construction/Litigation/Code Consultant - Retired
    www.AskCodeMan.com

  5. #5
    Join Date
    Oct 2014
    Location
    Maryland, DC, and Northern Virginia, electrical only
    Posts
    444

    Default Re: 1950s residential wiring . . . and 1950s residential wiring

    Understood and appreciated, Jerry. I know there are litigation risks when I offer halfway measures to customers who can't or won't do what's best from a safety vantage, however many caveats and warnings I put in. Forty-plus years without a claim doesn't mean I won't get smacked with a doozy tomorrow.


  6. #6
    Join Date
    Mar 2007
    Location
    Fletcher, NC
    Posts
    28,032

    Default Re: 1950s residential wiring . . . and 1950s residential wiring

    David, here's to continued good risk taking results.

    May The Force be with you (and continues to be with you).

    Jerry Peck
    Construction/Litigation/Code Consultant - Retired
    www.AskCodeMan.com

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