Thread: 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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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.

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

Originally Posted by Ken Amelin

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.

Thank you Mr. Watson.

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

Originally Posted by H.G. Watson, Sr.

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!

Yeah, I know this is an ancient thread, but I am exhuming it because it doesn't quite answer my question.

Does anyone know which code specifies the requirement of an EGC as a part of a cable assembly (NM-B or others)? I know in olden times, an EGC would sometimes be run separately, but is now required in the cable.

Originally Posted by Gunnar Alquist

Does anyone know which code specifies the requirement of an EGC as a part of a cable assembly (NM-B or others)? I know in olden times, an EGC would sometimes be run separately, but is now required in the cable.

Gunnar, going from memory, wh en grounding was required, the EGC was required to be run with the other conductors in the circuit, whether in conduit or in a cable.

The exception, as I recall, was when installing EGC for previously ungrounded outlets. In those cases, the EGC was allowed to be routed to separately from the other conductors of the circuit as it was run to a "grounding point" located as allowed by the code at the time the EGC was being added.

NM-B was a change in the conductor insulation temperature rating, from 60C to 90C, and was done for derating purposes (once it became recognized that 60C NM-A was not intended to be run in attics overs its ambient 60C design rating).

Table 310.15(B)(2)(a) Ambient Temperature Correction Factors based on 30C (86F) from the 2017 NEC for 60C conductor insulation ratings:

Ambient 50F or less ... 60C rating x 1.29
Ambient 51-59F ... 60C rating x 1.22
Ambient 60-68F ... 60C rating x 1.15
Ambient 69-77F ... 60C rating x 1.08
Ambient 78-86F ... 60C rating x 1.00
Ambient 87-95F ... 60C rating x 0.91
Ambient 96-104F ... 60C rating x 0.82
Ambient 104-113F ... 60C rating x 0.71
Ambient 114-122F ... 60C rating x 0.58
Ambient 123-131F ... 60C rating x 0.41
Ambient 132F and above ... 60C rating is not allowed to be used ... how many attics get to 132F during the summer, even in the northern states? Quite a few. Maybe most even.

Somewhere I had (not able to find it right now) a history of NM cable, which was first created in Rome, NY. The RomeX name was similar to the BX name, the 'X' was the 'experimental' product, which then went into production. At the time, there was NM, plain and simple. Then, as I recall, there was a need for higher temperature rated wire, so they changed the insulation and renamed the original Nm to NM-A, with the higher temperature product being NM-B. I also recall NM-C being from back then and it being (going from memory) 'corrosion resistant, with the 'C' indicating the corrosion resistant product.

Now that is the cool stuff that David like to dive into and may already have the information at his fingertips.

Jerry,

That is interesting. My previous home, built circa 1963, had thin EGC for the branch circuits and the EGC for the feed from the service equipment was a bare copper wire that was run next to the feeder cable.

As far as I can tell, this was not an upgrade or retrofit, this was as originally built. I thought I read somewhere in the NEC (or maybe a referenced standard) that integral EGC was first codified in the 1960s, but I have not been able to find it.

Gunnar, I'll look later, but my recollection is that (required grounding, i.e. EGC), came in with the 1959 NEC.

From the 1959 NEC:

250-52. Grounding a Circuit Conductor. The grounding conductor may be connected to the grounded circuit conductor at any convenient point on the premises on the supply side of the service disconnecting means.

I.e., basically the same as now, except that it was deemed necessary to clarify: Hey, you! Yeah, you! That DOES NOT say that you can ground the grounded conductor 'at any point on the load side of the service disconnect'! Except that it is stated nicer: The grounded conductor shall not be bonded to ground on the load side of the service disconnecting means.

250-53. Common Grounding Conductor. The grounding conductor for the circuits may also be used for grounding equipment, conduit, and other metal raceways or enclosures for conductors, including service conduit or cable sheath and service equipment.

I.e., "common grounding conductor" is essentially the same conductor and use as the current "equipment grounding conductor".

Article 100 Definitions: Grounding Conductor: A conductor used to connect an equipment, device, or wiring system with a grounding electrode or electrodes.

210-7. Grounding Receptacles. blah, blah, blah, the branch circuit or branch circuit raceway shall include or provide a grounding conductor to which the grounding contacts of the grounding receptacle shall be connected. The metal armor of the armored cable or metallic raceway is acceptable as a grounding conductor.

I.e., that does not state that the grounding conductor may be strapped to the outside of the branch circuit (repeat "Hey, you! Yeah, you! ... ").

Many code changes are done to specifically state what was originally intended because one or more contractors try to find a way around what the code stated "branch circuit ... shall include".

Granted, those code change wordings are not the only reason the code went from a 4x7x1" thick book to what it is now, but those "this is what we meant wording clarifications" have added a lot to the code.

Originally Posted by Gunnar Alquist

My previous home, built circa 1963, had thin EGC for the branch circuits ...

The EGC you describe was, or was not, part of the cable?

I read the GEC as being strapped outside what it was run with. Or am I reading that incorrectly?

In the 1959 NEC days, the "common grounding conductor" was basically all inclusive of EGC, GEC, and other now separately named sections of the overall grounding conductor run.

While it could have worked the other way around, I rather suspect that the tail wagging that dog vor inclusion of the conductor in the cable was UL 719, the NM standard.
The fifth edition was adopted in 1957, the six, 1968. I doubt they are accessible anywhere except conceivably via the creeps at internet archive.
It is common for stakeholders represented on NFPA Code Making Panels to also have a seat at the table making and updating related product standards.
I imagine the process going about as I've seen it elsewhere. A company comes up with a product enhancement, such as GFCIs' self-testing. It sells. A few years later, they push the enhancement for acceptance in the product standard, UL 943. In the case of that one, they had to license the technology at an accepted price, but hey, they still had a lead. Meanwhile, all these companies and NRTLs were involved in the NEC process. 210.8 doesn't specify self-testing, but requires Class A GFCIs, and UL 943 is one of the referenced standards.

Originally Posted by david shapiro

While it could have worked the other way around, I rather suspect that the tail wagging that dog vor inclusion of the conductor in the cable was UL 719, the NM standard.

When I was on UL STC 67, we didn't create requirements for standards. We tuned and fine tuned standards to reflect what the code said.

Good for you, Jerry. It has to work every which way. I remember rules coming into the NEC that required use of equipment that wasn't yet on the market, so generally installers were expected to continue with previous practices.

Originally Posted by Jerry Peck

The EGC you describe was, or was not, part of the cable?

I read the GEC as being strapped outside what it was run with. Or am I reading that incorrectly?

In the 1959 NEC days, the "common grounding conductor" was basically all inclusive of EGC, GEC, and other now separately named sections of the overall grounding conductor run.

Hi Jerry,

Sorry for the late reply. I am currently spending some time with friends and this is the first I have checked my computer.

The feed from the service equipment to the interior panel was an old three-wire stranded aluminum, cloth-wrapped NM cable (the cloth wrap was silvery/green). The EGC for the feed between the service equipment to the interior panel was a separate, bare copper, I believe #6 conductor. Not strapped, but run more-or-less parallel. Same hole up from the service equipment, same hole down to the interior panel, but in some places it was a foot or two from the NM cable.

The branch circuit NM cables were two-wire with ground. The current-carrying conductors were (depending on the circuit) #14 or #12 copper and the integral EGC was this teeny (maybe #16, maybe #18) bare copper that was part of the manufactured cable. These also had the silvery/green cloth-wrapped sheathing.

I figure that the concept was that if the EGC was carrying current, it would do so for a few seconds until the breaker tripped, so it did not need to be full-sized, but this was changed with the next code cycle. I have only seen it a few times, always custom homes from the early 1960s.

Originally Posted by Gunnar Alquist

The feed from the service equipment to the interior panel was an old three-wire stranded aluminum, cloth-wrapped NM cable (the cloth wrap was silvery/green). The EGC for the feed between the service equipment to the interior panel was a separate, bare copper, I believe #6 conductor. Not strapped, but run more-or-less parallel. Same hole up from the service equipment, same hole down to the interior panel, but in some places it was a foot or two from the NM cable.

Gunnar, that looks like it was the "common grounding conductor" referred to in the 1959, and which was later separated into the various sections (GEC, EGC, etc).

I think that panel was originally, as David mentioned, the original service equipment panel. The panel was replaced to update it, but what was the service equipment cable, which should have been replaced, was repurposed for use as a feeder ... which never ever was allowed as such. To 'solve' that issue (in their minds, and maybe in an inspectors mind to ... ro not ... i.e., unpermitted work), the person doing the electrical work (I am avoiding saying "the electrical contractor") may have installed that as the EGC for the cable (but it may have originally been the GEC for the service equipment).

The branch circuit NM cables were two-wire with ground. The current-carrying conductors were (depending on the circuit) #14 or #12 copper and the integral EGC was this teeny (maybe #16, maybe #18) bare copper that was part of the manufactured cable. These also had the silvery/green cloth-wrapped sheathing.

When EGC first came into being, they were allowed to be smaller than the two circuit conductor were. I'm not sure what the smallest size they were ever allowed to be, but I also recall having seen some old EGC which looked to be 16 AWG (because they did not look to be the same size as the 14 AWG conductors in the old NM).

- - - Updated - - -

Originally Posted by david shapiro

Good for you, Jerry. It has to work every which way. I remember rules coming into the NEC that required use of equipment that wasn't yet on the market, so generally installers were expected to continue with previous practices.

I seem to have that memory in the back of my head, but what I remember better is that things came on the market for which there was no specific code for, yet were actually addressed by one section of the code: 110.3(B). Installed in accordance with the manufacturer's installation instructions (listed or not listed back before "listing and labeling" became the thing.

Generators come to mind.

Now there are several categories of generators.

Originally Posted by Jerry Peck

Gunnar, that looks like it was the "common grounding conductor" referred to in the 1959, and which was later separated into the various sections (GEC, EGC, etc).

Jerry,

I do recall learning that at some point. The year that occurred is of interest to me and I hope to look it up one day.

Originally Posted by Jerry Peck

I think that panel was originally, as David mentioned, the original service equipment panel. The panel was replaced to update it, but what was the service equipment cable, which should have been replaced, was repurposed for use as a feeder ... which never ever was allowed as such. To 'solve' that issue (in their minds, and maybe in an inspectors mind to ... ro not ... i.e., unpermitted work), the person doing the electrical work (I am avoiding saying "the electrical contractor") may have installed that as the EGC for the cable (but it may have originally been the GEC for the service equipment).

I have seen the repurposed panels a number of times in the past. I am 99.9% sure that this particular panel was original to the home and installed as the branch circuit panel. This was located quite far (easily 60 feet horizontally) from the overhead service entrance and service equipment. In my area, the service equipment is nearly always on the exterior of the home, as it was in this case and everything looked original. An exterior main disconnect has been utility requirement for many moons (I do not recall exactly when it started, but I could probably find out). The service equipment was also an old Zinsco with a 100 amp main disconnect breaker.

Originally Posted by Jerry Peck

When EGC first came into being, they were allowed to be smaller than the two circuit conductor were. I'm not sure what the smallest size they were ever allowed to be, but I also recall having seen some old EGC which looked to be 16 AWG

I seem to have that memory in the back of my head, but what I remember better is that things came on the market for which there was no specific code for, yet were actually addressed by one section of the code: 110.3(B). Installed in accordance with the manufacturer's installation instructions (listed or not listed back before "listing and labeling" became the thing.

That would explain why I have been unable to find a reference as to minimum EGC (or "common grounding conductor) size. At one time I knew what size these EGCs were, but have since forgotten.

Thanks for the information.

Gunnar, I looked back through the 1959 NEC again and read some more about the "common grounding conductor", such as in 250-92 Installation (way too much to type here); however ...

- 250-92 Installation. Grounding conductors shall be installed as follows:
- - (a) System or Common Grounding Conductor. blah, blah, blah (half of the paragraph) ... Grounding conductors smaller than No. 6 shall be in conduit, electrical metallic tubing or cable armor. blah, blah, blah (the second half of the paragraph).

With NM cable, I suppose the outer sheath would be considered to be the "cable armor".

Ah ha ... what I looked for before but didn't see it (probably stopped looking just before I got that far as I had looked at the previous page before and found Table 250-94(a) Sizes of Grounding Conductors and Table 250-94(b) Sizes of Grounding Conductors, flipped the page over and there was no Table 250-94(c) ... so I flipped the page back over) Table 250.95.

Table 250-95 is also titled "Sizes of Grounding Conductors".

- Table 250-95 Sizes of Grounding Conductors.
- - (see attached, and note the "*" by "16*")

Thank you Jerry! That is one of the fun things with the NEC. Occasionally, some critical piece of information is cleverly placed in an exception, informational note, or as in this case, behind an asterisk.