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Need a lesson on this wiring type


Robert Jones
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That would be fairly normal, original wiring for the period. It's usually referred to as "cloth covered NM cable". Nothing wrong with it except, of course, it lacked a grounding wire at that time (which became the norm shortly after...early 60's if I have that right). It doesn't have the same issues as knob and tube, but to bring the home up to modern standards you would still need to run newer "romex".

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Home built in 1957. This was the predominate wiring that was visible in the attic and crawl space. All of the outlets were 2 prong or 3 prong(ungrounded). Was this wiring an update at some point? Or was it used in the mid fifties? Not finding any answer from the magic of google.

As Richard said, it's the standard NM of the period. It's more easily damaged by heat than modern NM so you might find that it's damaged just above ceiling fixtures or other places where it'd be exposed to high temps. Other than that, I've never heard that its been particularly troublesome.

- Jim Katen, Oregon

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In these parts, that wiring has a ground conductor in it. It's marked something like NM #14/2. What would the marking be without a ground?

If it's from the mid 50's, I doubt it would have a ground. Braided stuff in a home from the early 60's onward probably does have a ground but it would still look much the same. As for markings, today's grounded NM cable actually has a W/G (or sometimes the words "With Ground") marked on it as in "14/2 W/G". The photo below is from a 1964 home and you can see (sort of) it says "14/2 WITH GROUND TYPE NM". I'm guessing the older ungrounded stuff would just say 14/2.

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tn_20102993713_1964-nm.jpg

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This is from "Residential Electrical System Aging Research Project", a link someone kindly posted here earlier this year. Page 17 at http://www.nfpa.org/assets/files//PDF/R ... Report.pdf

Quote: Until the early 1960s, most NM cable for residential use did not have a grounding conductor. However, changes in the 1962 NEC that mandated equipment grounding for all branch circuits popularized the use of NM cable with ground.

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