# Odd 1940's NM



## BrightLight (Jun 24, 2009)

Just looked at a job here in LA. The house was supposedly built about 1943.

Saw in a receptical box what looked to be NM. Rubber with cloth. The "cable" seemed to consist of one insulated conductor, and one un-insulated conductor. The insulated seem was wired top the hot side of the receptical, and the uninsulated wire to the neutral. 

The box seemed to be much newer than the wire, and there was no stain relief.

Looked in another box supporting the front porch light. That box looked to be original, and again one insulated conductor, one not.

The client is renting the house out, and I did not want to talk in front of the tenant.

Has anyone seen this sort of NM? I have not. I have see plenty with two insulated conductors, all sorts of rubber and cloth, without a ground wire. But never this.

Anyone?


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## jwjrw (Jan 14, 2010)

Whatever it is.....it's not nm.


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## RIVETER (Sep 26, 2009)

It was common, even into the seventies to have a non-insulated neutral.


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## drsparky (Nov 13, 2008)

How about a photo!


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## 480sparky (Sep 20, 2007)

RIVETER said:


> It was common, even into the seventies to have a non-insulated neutral.



First I've ever heard of NM having bare neutrals, even though it has been illegal since, oh, 1923.


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## ampman (Apr 2, 2009)

480sparky said:


> First I've ever heard of NM having bare neutrals, even though it has been illegal since, oh, 1923.


 me neither but i learn somthing new all the time


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## BrightLight (Jun 24, 2009)

I do know that a lot of compromises were made during the war.

Heard of a ceiling collapsing because the wall board was only barley nailed up. When the wallboard on the walls was pulled off, that was just about all that was supporting the ceiling.

While this sort of cable may have been superceeded many years prior, it might have been the only stuff readily available in 1943....

Anyway, I'm telling the client that he needs to brace himself for a fair bit of re-wiring.

And how is it NOT NM? The only thing about it that is metallic are the two copper conductors.


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## RIVETER (Sep 26, 2009)

480sparky said:


> First I've ever heard of NM having bare neutrals, even though it has been illegal since, oh, 1923.


You are starting to show your age.


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## 480sparky (Sep 20, 2007)

RIVETER said:


> You are starting to show your age.



Eh?!?! What'd you say sonny?

Damn punk kids. Now get off my lawn!


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## RIVETER (Sep 26, 2009)

480sparky said:


> Eh?!?! What'd you say sonny?
> 
> Damn punk kids. Now get off my lawn!


I'm sorry; I'll try to be more respectful. Actually, I don't know if it was NM, or not. I was just referring to the use, in general, of an uninsulated neutral until it was realized that it was dangerous.


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## BrightLight (Jun 24, 2009)

RIVETER said:


> I'm sorry; I'll try to be more respectful. Actually, I don't know if it was NM, or not. I was just referring to the use, in general, of an uninsulated neutral until it was realized that it was dangerous.


The main hazard being that the box can readily become energized by the neutral touching it?

What kills me (!) is that the house has seen substantial electrical upgrades, including a modern circuit panel. There is modern NM up in the attic, some patched straight into the old stuff without the benefit of a j-box. Ick.

And just mountains of blown in insulation. Just to make it interesting.


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## RIVETER (Sep 26, 2009)

The problem with an uninsulated neutral is the fact that when it comes in contact with any metal object it just rests there and causes no problem because of its potential. Any other thing that comes in contact with that metal becomes a potential parallel path for the circuit current. It would not be a measurable voltage with a tester but to be in series with circuit current is a very serious incident.


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## MDShunk (Jan 7, 2007)

That cable you describe sounds a lot like the "covered neutral" UF cable that was used around that time to feed post lights, detached garages, etc. It was used in place of, but during the same time period as, lead sheath cable.


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## jwjrw (Jan 14, 2010)

MDShunk said:


> That cable you describe sounds a lot like the "covered neutral" UF cable that was used around that time to feed post lights, detached garages, etc. It was used in place of, but during the same time period as, lead sheath cable.


 
I actually have a piece of that lead sheath cable in the garage I dug up and saved.


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## BrightLight (Jun 24, 2009)

MDShunk said:


> That cable you describe sounds a lot like the "covered neutral" UF cable that was used around that time to feed post lights, detached garages, etc. It was used in place of, but during the same time period as, lead sheath cable.



And you would agree that the only responsible thing to do is to tear it out and replace it with modern cable.


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## MDShunk (Jan 7, 2007)

BrightLight said:


> And you would agree that the only responsible thing to do is to tear it out and replace it with modern cable.


I would say that the cable does not meet the present day code, but may have met code at the time it was installed. That's about as far as I'm willing to go on existing nonconforming installations.


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## BrightLight (Jun 24, 2009)

MDShunk said:


> I would say that the cable does not meet the present day code, but may have met code at the time it was installed. That's about as far as I'm willing to go on existing nonconforming installations.


Fair enough.


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## RIVETER (Sep 26, 2009)

BrightLight said:


> The main hazard being that the box can readily become energized by the neutral touching it?
> 
> What kills me (!) is that the house has seen substantial electrical upgrades, including a modern circuit panel. There is modern NM up in the attic, some patched straight into the old stuff without the benefit of a j-box. Ick.
> 
> And just mountains of blown in insulation. Just to make it interesting.


Visualize this. You are working in a store at a shopping center and you are above the ceiling and notice that a run of EMT has come loose at the coupling from a previous install. You are tempted to just push them together and tighten. You grab one end with your left hand and the other with your right...and you notice a bare neutral there, as well.


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## BrightLight (Jun 24, 2009)

RIVETER said:


> Visualize this. You are working in a store at a shopping center and you are above the ceiling and notice that a run of EMT has come loose at the coupling fom a previous install. You are tempted to just push them together and tighten. You grab one end with your left hand and the other with your right...and you notice a bare neutral there, as well.


Yes. Ugh. You are likely to become the path for the current on the neutral to the ground via the emt.

Very exciting. The good news is that you are likely to get thrown off you ladder. The bad news is the ladder is 24' high.

I would not mind knowing when it is that people figured this out and the code was changed. As I said, I bet this stuff was rattling around in a warehouse somewhere when the contract to build a house in the middle of WW2 came down. 

Housing in the San Fernando Valley spread quite sporadically. The block I live on was sub-divided in the early 20's, and the house next to mine was built in '28. Mine was built in '48. And there are homes on the block that were not built until the sixties, I think.

So a house could be built years apart from the ones on either side. And there was almost no metal available on the market during the war. Copper included. Where the contractor found the plumbing, I don't know.


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## davey (Aug 14, 2010)

1943 Supplement to the 1940 NEC:
*Section 3372. With Uninsulated Conductor. (New section). Interim Amendment No. 43 Approved April 9, 1942.

Add a new section 3372 to be effective only for the duration of the emergency. 
3372. With Uninsulated Conductor [for neutral only]. . . .may be used in defense emergency buildings of occupancies other than listed in 1 to 7 in section 3362. Such cable shall not be used on circuits exceeding 208 volts to ground, nor for circuits beyond the final cable branch-circuit outlet [surface or fixture] nor for extensions to existing branch circuits on which all conductors have individual insulation. [Bond distribution--downstream!--cabinets to it.] [Boxes and covers should be nonmetallic.] 

Then Section 3382 okayed SE for ranges, water heaters and feeders to other buildings.


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## BrightLight (Jun 24, 2009)

davey said:


> 1943 Supplement ....for the duration of the emergency.


Almost exactly when the home is supposed to have been built....


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## Big John (May 23, 2010)

RIVETER said:


> Visualize this. You are working in a store at a shopping center and you are above the ceiling and notice that a run of EMT has come loose at the coupling from a previous install. You are tempted to just push them together and tighten. You grab one end with your left hand and the other with your right...and you notice a bare neutral there, as well.


...And then you push the pieces of conduit into the coupling and tighten the screws.

I'm not saying that a bare neutral is the safest thing ever. I've had calls where people were getting slight shocks from equipment with a bonded neutral. But in a case where a neutral is intact back to the source, unless you're barefoot in a pool of water, there's probably not gonna be enough voltage there to shock you. That's why neutral-bonding was code compliant in many applications, and which is basically what an uninsulated neutral is.

-John


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## davey (Aug 14, 2010)

I'm with you, John. 

Still, that's a big "if" we talk about when we say "where the neutral is intact all the way home; big in the sense of it makes all the difference. And we've all been on jobs where this wasn't as true as we'd like. Besides, my "tingle" is the next person's (child's) (sick old lady's) bad news.


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## BrightLight (Jun 24, 2009)

davey said:


> I'm with you, John.
> 
> Still, that's a big "if" we talk about when we say "where the neutral is intact all the way home; big in the sense of it makes all the difference. And we've all been on jobs where this wasn't as true as we'd like. Besides, my "tingle" is the next person's (child's) (sick old lady's) bad news.


Yeah, I've had the stuff go up my arm, thru my chest (and presumptively my heart) and down my other arm. I danced for a few seconds before I could pull away. I was 30. Twenty years later and many pounds heavier, and I wonder if I would survive that.


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## davey (Aug 14, 2010)

That does a great job of making the point about Code year not necessarily being the same as locally adopted year.

The next NEC, the 1947, leaves 3372 out.


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## Shockdoc (Mar 4, 2010)

davey said:


> That does a great job of making the point about Code year not necessarily being the same as locally adopted year.
> 
> The next NEC, the 1947, leaves 3372 out.


And during the present war that started in 2002 the NEC required more than less. Go figuire.


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## amptech (Sep 21, 2007)

I have seen a ot of this type of cable in homes built between the 30s and 40s. Usually, it is #10 with a stranded bare that spirals around the insulated conductor which is covered with a rubber outer jacket. It usually is found feeding a 4 fuse block on a second floor. I have also seen it in 12ga and used for branch circuits. I don't know if it was a WWII conservation thing since I've seen it in several houses built prior to 1940.


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## SparkYZ (Jan 20, 2010)

I wonder where in the San Fernando Valley this is...most of my residential work has been in SFV, and Ive never seen this cable


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## BrightLight (Jun 24, 2009)

SparkYZ said:


> I wonder where in the San Fernando Valley this is...most of my residential work has been in SFV, and Ive never seen this cable


Burbank, just south of the airport, right by North Hollywood. A block or two north of Victory.


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## Shockdoc (Mar 4, 2010)

I've seen the stuff before , looks like old 10/3 snakeskin, one conductor center and the other spiraled. Seen it mostly in old motels as individual unit feeders,.


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