Old NM with different insulation thickness, Has anyone seen this?

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tortuga

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
Greetings As some of you know I am interested in old electrical systems.
I have run across this strange NM a only a few times, and I last time I ran across it I was able to remove a sample.
Its older NM cable with different insulation thickness, the balck is a normal size then there is a white with smaller insulation. Has anyone seen this?
20180228_210200.jpg

I am curious what its original intended application or UL listing was. And if the smaller white conductor was approved as 600V insulation at the time?

20180228_210210.jpg

I have now seen enough of it to know it was not a manufacturing mistake.
 
My guess is these are two versions of the same thing: well-insulated hot wire and no/minimal insulation on the grounded conductor.
 
gadfly56 said:
In the thread referenced, the neutral is bare. In this case, it's covered but there is a discrepancy in the thickness of the insulation.
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Yup. But, you see, I'm asking about the history of the building in Tortuga's experience of collecting his specimen.
 
al hildenbrand said:
Take a look at Post # 9 in the Old Cloth Wiring with bare neutral. Does that seem to make a connection to the history of the buildings that yours comes from?
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Wow yes its a single family home, obviously lots of additions and remodeling. Two story. The second floor is very loft like, Possibly a converted attic. I just looked the house up on the county website and it was 'built' in 1945, meaning added to the tax rolls but I doubt there were many permits pulled.
Its in a suburban neighborhood, after thinking about it its probably the oldest home around there.
We were converting the service from overhead to underground and found the service entrance conductors from the meter to the load-center were old fine strand welding cable to a rusted out exterior breaker box.
So we just replaced the whole thing.. A few of the old cables would not reach so then we replaced a few 'home runs'.
Classic can of worms job.
I had our crew put all the 120V 20A&15A circuits on AFCI/GFCI breakers due to this unusual cable combined with the presence of ungrounded 3 prong receptacles throughout the house.
I kept a sample of the cable threw it in a box and forgot about it till I was cleaning out some old boxes yesterday.
Funny timing for two threads about the same thing.

So I guess it was even a code violation at the time....
 
Maybe its not insulation, but just to prevent the copper from sticking when the jacket is applied? Just wild guess.
 
tortuga said:
So I guess it was even a code violation at the time....
Click to expand...
I'm not so sure. The NEC had editions published in 1940, 1942, 1943 and 1947. I have never been able to get my hands on copies of the '42 and '43. I'll just bet that the historic NM cable that you have was given the reduced covering to permit "identification" of the grounded conductor.

Your sample reminds me of some of the early NM with ground that I helped install in new construction while I was in my first year as an apprentice electrician. I was working under the 1965 NEC. NM cable of that day was still transitional from no EGC at all to the "reduced guage" EGC that was a # 16.

Some of the cable manufacturers of the Reduced EGC type NM cable made their # 16 guage EGCs with a green thermoset plastic coating. The green plastic coating wasn't uniform, either. . . think of the shape of ordinary two conductor STP-1 (zip cord or lamp cord) and imagine one conductor is the # 16 copper EGC and the other is solid thermoset plastic. The basic cross-section is a figure eight, and the thermoset plastic is green all the way through.

The green covering on the reduced guage EGC in Early Sixties NM with ground was neither required, nor was it prohibited.

NM EGC conductors lost the green coating early on, but for a while it was available from some manufacturers. I can easily suspect that the choice of green covering was to help the installer "get it right" that this was an EGC, not some form of an uninsulated neutral.

So, Tortuga, in your case, the white tinted covering could easily have been a similar "helpful" feature placed by a cable manufacturer, neither required, nor prohibited.
 
If you notice, the white marking on the neutral of those old conductors eventually goes away, especially in fixture boxes. Sure would be nice to know that the skinnier conductor is the neutral.

-Hal
 
Since it was around the end of WWII & wartime shortages could it be the case of the manufacturer using what was available? A circa 1943 prefab house used a NM cable that had a paper spiral wrap around the individual conductors, never have seen it anywhere but those houses, but doubt they were intended to last beyond the duration of the war, they also used friction tape to extend too short cables/ utilize all material, but it had been disconnected since around 1980 or so.
 
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