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  1. #1
    Join Date
    Mar 2007
    Location
    Cape Cod, Massachusetts
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    574

    Default Old romex wire with ground

    This house was built in the 20's but not sure when the wiring was installed or manufactured.

    It's unusual to me in that the grounding conductor is covered with a green insulator and the insulator looks like it may be split with two grounding conductors?

    Is anyone familiar with this type of wiring or any info on history?
    Thanks

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    Ken Amelin
    Cape Cod's Best Inspection Services
    www.midcapehomeinspection.com

  2. #2
    Robert Meier's Avatar
    Robert Meier Guest

    Default Re: Old romex wire with ground

    There should be nothing wrong with it. I have seen that type of cable in the past and from what I remember the green EGC insulation was more oblong or rectangular than round.


  3. #3
    Join Date
    Dec 2007
    Location
    Chico,Ca
    Posts
    423

    Default Re: Old romex wire with ground

    It's likely to have a reduced EGC (16 AWG) also, it was common in the late 1960's.


  4. #4
    Join Date
    Jul 2008
    Location
    Snowbird (this means I'm retired and migrate between locations), FL/MI
    Posts
    4,086

    Default Re: Old romex wire with ground

    Quote Originally Posted by Ken Amelin View Post
    This house was built in the 20's but not sure when the wiring was installed or manufactured.

    It's unusual to me in that the grounding conductor is covered with a green insulator and the insulator looks like it may be split with two grounding conductors?

    Is anyone familiar with this type of wiring or any info on history?
    Thanks
    Nonmetallic Cable

    Although nonmetallic-sheathed cable, or NM for short, was first listed and described in the NEC in 1926, it was actually invented a few years earlier by General Cable at their Rome Wire Divison in Rome, NY, and marketed under the trade name "Romex". Today many installers still refer generically to NM cable as Romex.

    Early NM cable had their individual conductors jacket wrapped in a cotton braid that was impregnated with either a varnish or a tar-like substance for moisture protection.

    Around 1950, synthetic spun rayon was being permitted to replace the cotton thread in the jacket braid. Then in the early 1960s, thermoplastic began replacing the braided jacket altogether, and by about 1970, most all NM cable had a PVC outer jacket, although a braid was still permitted until 1984. Also in 1984, NM-B cable was developed and required to have 90 degrees C rated individual conductors, and a 75 degrees C outer jacket.

    Until the early 1960s, most NM cable for residential use did not have a grounding conductor. However, the changes in the 1962 NEC that mandated equipment grounding for all branch circuits popularized the use of NM cable with ground. Earlier versions of NM cable with ground permitted the grounding conductor to be No. 16 AWG for 14 and 12 gauge copper NM, and No. 14 AWG ground for 10 gauge copper NM. In 1969, new requirements no longer permitted an undersized grounding conductor for 14, 12, and 10 gauge NM cable.

    Keep in mind that although UL listings for manufactured products would be up to date to the current edition of the NEC at the time of manufacture, few jurisdictions were up-to-date with their adoptions of same. It was always perfectly legal to sell off already produced product and continue to use what was in inventory - as long as where it was installed was to the edition/version (ammendments) of the local jurisdiction or authority's adoption. Some areas, such as NE Ohio and NE Illinois, for example did not permit NM (and most of NE Illinois still does not). NE Ohio was common to find K & T in new installations up to the early 70s.



  5. #5
    Join Date
    Mar 2007
    Location
    Cape Cod, Massachusetts
    Posts
    574

    Default Re: Old romex wire with ground

    Thank you Mr. Watson.

    Very informative!. I will cut paste this info and put it in my library.

    Ken Amelin
    Cape Cod's Best Inspection Services
    www.midcapehomeinspection.com

  6. #6
    cuba_pete's Avatar
    cuba_pete Guest

    Default Re: Old romex wire with ground

    Quote Originally Posted by H.G. Watson, Sr. View Post
    Early NM cable had their individual conductors jacket wrapped in a cotton braid that was impregnated with either a varnish or a tar-like substance for moisture protection.
    I just pulled a couple hundred feet of that stuff out of my family's lake cabin two weeks ago. I am going back tomorrow to finish the complete rewiring of the cabin.

    I just so happen to have the MSDS for one of the popular compounds that was used to make these impregnated cotton/cloth/jute wires and cables. It is maintained by a company called Solar Compounds Corporation and is identified as "Mix 96". It's identified on the MSDS as Petroleum Asphalt. Nice...that's one reason why house fires poison people.

    We had to provide an environmental impact statement to the the states of California and Washington for some of my work locations which still have this product directly buried. Your tax dollars at work!


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