Old romex

[keith gigabyte]

What’s everyone’s opinion on old romex with smaller ground.
adding an outlet and want to tap into old romex with smaller egc

 

[Clodbuster]

My opinion is it's better than no ground. I have some in my house and I don't worry about it. Your inspector may not agree with its suitability when extending a circuit however.

 

[al hildenbrand]

Depending upon the local installation procedure history for your jurisdiction, there may be an issue with the manner in which the reduced gauge EGC (Equipment Grounding Conductor) was bonded / spliced at the junction boxes that the branch circuit passes through. The transition to incorporating a wire-type EGC at every outlet or device box was a slow educational process that had to happen individual installer by individual installer.

Some installers and AHJs approved just folding the EGC back, in one manner or another, others allowed simply twisting the wires without using a pressure connector, and bonding to the metal enclosure came later.

If the reduced gauge EGC in your job is actually spliced and bonded to the conductive boxes all the way along the Branch Circuit back to the Overcurrent Protective Device, then, in my opinion, you are good to extend. . . but, as Clodbuster suggests, a quick check with your AHJ would still be prudent.

The concern is whether there is actually an "effective low impedance fault clearing path."

 

[peter d]

The problem is the reduced EGC is not listed in the NEC as a compliant EGC anymore, so I would say that extension of those circuits are not allowed per the NEC. Now, in reality, these circuits get extended all the time.

 

[drcampbell]

... The transition to incorporating a wire-type EGC at every outlet or device box was a slow educational process that had to happen individual installer by individual installer. ...

More succinctly, one funeral at a time.


Question 1: Is this reduced-size EGC even continuous all the way back to the building grounding/bonding point?
If so, are the connections tight and secure? I've seen many installations where the EGCs are merely loosely twisted.

Question 2: Assuming it's continuous, is it adequate?
When it was installed, maybe. It was common to provide 60-amp service with 50-100 mΩ source impedance and a maximum short-circuit fault current of maybe 1-2 kA. There were usually fuses, which while not specifically "current limiting" -- that concept would emerge decades later -- they did provide some current limiting.

Today, probably not. There's much more fault current available and breakers provide no current limiting.

Especially if the EGC is two sizes smaller, as I've occasionally seen.
http://forums.mikeholt.com/showthread.php?t=175663

 

[al hildenbrand]

It was common to provide 60-amp service with 50-100 mΩ source impedance and a maximum short-circuit fault current of maybe 1-2 kA. There were usually fuses, . . .

In the 1962 NEC, 230-71 Exception No. 1 required a minimum 100 Amp service in Dwellings that, by Article 220, had a calculated 10 kW load (or more.) Each successive Code cycle made it harder to avoid, until 100 Amp was the minimum allowed.

Power companies and the general homeowner all believed in the emerging Atomic Age and how an all-electric future was coming where the power company meter would be unnecessary.

I apprenticed during the reduced EGC period, and none of the new construction dwelling services I helped my Master install were fuse. They were all the "height of modernity," being circuit breakers. (GE THQP, split bus, mostly. . . but that is another story.)

As an aside, the available current assumptions in your linked thread are more Pre-WWII, in my opinion.

 

[romex jockey]

sheesh , and i thought i was a dinosaur , ok so..... just because i meter out an EGC in an older system, how do we verify it? You guys might recall the same concern with old BX

RJ~

 

[Craigv]

What’s everyone’s opinion on old romex with smaller ground.
adding an outlet and want to tap into old romex with smaller egc

1. Verify that the EGC is continuous back to the panel. If it isn't, recommend a full circuit replacement.

2. If it is continuous: Find and inspect the path through any boxes. If the EGC is merely pulled back through and twisted around the cable, or is merely twisted to other EGC's in the boxes, install pressure connectors, bond properly to the boxes, and recommend a full circuit replacement before extending the circuit.

My opinion of this is that regardless of code interpretations, local grandfathering, etc., when you touch it, you own it...a lawyer will make sure of this if something tragic happens. As already mentioned, fault current potential is far higher today than it was when this was an accepted wiring method, and the potential for a fire to start before OCPD trips is real.

 

[al hildenbrand]

As already mentioned, fault current potential is far higher today than it was when this was an accepted wiring method, and the potential for a fire to start before OCPD trips is real.

I disagree with this. Through the decade of the 1960s we lived in the Early Atomic Age. Central Air Conditioning, Heat Pumps, Electric Ranges, Electric Water Heaters, Electric Clothes Dryers, Electric Furnaces, Disposals, Dishwashers, Submersible Wells, etc. all existed and were provided for as the builder designed the Dwelling. The Power Company transformers installed then are, in my opinion, still the same size they were when the subdivision was electrified in the Sixties, with an occasional exception. The length of the PoCo secondary conductors and the dwelling service lateral or drop has not "shortened" nor has it been replaced with heavier gauges in most of the cases. The PoCo philosophy that if their circuit doesn't burn down, it's safe to continue, is still firmly entrenched, in my opinion.

Let me say that again. The subdivision wired by the PoCo during the decade of the Sixties (the decade that reduced EGCs were installed in Dwelling Branch Circuits) has, in my opinion, largely the same sized transformers today.

The transformers aren't moving closer to the house and the branch circuit impedance (think wire gauge) isn't decreasing because the #14 (or #12) is somehow gaining Copper.

The Sixties end-of-small-gauge-branch-circuit fault current of 70 to 200 Amps is still what is available, today, in most cases, in my opinion.

 

[sameguy]

Can you add larger wire to a smaller one to make up for voltage drop?
Say #12 out then add a #10.

 

[GoldDigger]

Can you add larger wire to a smaller one to make up for voltage drop?
Say #12 out then add a #10.

Putting in a larger wire to extend a circuit does not counteract (reduce) existing voltage drop. It just make the voltage drop in the piece of wire that you add smaller.

If the voltage drop in the existing #12 is already too high, that is the wire that you need to replace.

It is a bit like the race driver who needed to make a sixty mile trip in under two hours:
He drove the first 40 miles at 20MPH, planning to make up the time by going really fast over the last 20 miles. (Work out the numbers :angel

On the other hand, if you have an existing 50 foot run of #12 and you have to extend it another 50 feet, then maybe using #10 instead of #12 for that extension might make sense. Depends on what your existing VD is and what your target is for the whole run.

 

[sameguy]

My point, I wouldn't worry about the reduced ground.

 

[drcampbell]

If what you say is true, it was never really adequate to assure fault clearance.

.... The Sixties end-of-small-gauge-branch-circuit fault current of 70 to 200 Amps is still what is available, today, in most cases ...

If my calculation is correct, a 40-amp fault current for two minutes (the spec for a 20-amp breaker) will result in a 500° temperature rise in a 16-gauge copper wire.
Feel free, of course, to check my work.
http://forums.mikeholt.com/showthread.php?t=175663

... I apprenticed during the reduced EGC period, and none of the new construction dwelling services I helped my Master install were fuse. They were all the "height of modernity," being circuit breakers. ...

I was a little kid at the time, but learned later that our house had a panel upgrade in 1962, and a new fusebox was installed. It's probably a 100-amp box, with about 16 screw-in Edison-base fuses. It's in Chicagoland and all EMT, so the reduced-size EGC in NM cable isn't an issue. Gas heat, gas stove, gas water heater and no air conditioning at the time. I have no idea what the capacity/impedance of the POCO's circuit was/is. The house and neighborhood were built in about 1910.

 

[romex jockey]

I've been pivy to many 'boston backwrap' 60's ragwiring.

I'm sure you fellas have seen your share, but i'll post a pix anyways>

most of the time they'll ring out/meter an egc. but it's not continuous, and no where near modern art 250 standards

what to do with it?

~RJ~

 

[LarryFine]

It is a bit like the race driver who needed to make a sixty mile trip in under two hours:
He drove the first 40 miles at 20MPH, planning to make up the time by going really fast over the last 20 miles. (Work out the numbers :angel

Can't be done.

 

[Craigv]

I disagree with this. Through the decade of the 1960s we lived in the Early Atomic Age. Central Air Conditioning, Heat Pumps, Electric Ranges, Electric Water Heaters, Electric Clothes Dryers, Electric Furnaces, Disposals, Dishwashers, Submersible Wells, etc. all existed and were provided for as the builder designed the Dwelling. The Power Company transformers installed then are, in my opinion, still the same size they were when the subdivision was electrified in the Sixties, with an occasional exception. The length of the PoCo secondary conductors and the dwelling service lateral or drop has not "shortened" nor has it been replaced with heavier gauges in most of the cases. The PoCo philosophy that if their circuit doesn't burn down, it's safe to continue, is still firmly entrenched, in my opinion.

Let me say that again. The subdivision wired by the PoCo during the decade of the Sixties (the decade that reduced EGCs were installed in Dwelling Branch Circuits) has, in my opinion, largely the same sized transformers today.

The transformers aren't moving closer to the house and the branch circuit impedance (think wire gauge) isn't decreasing because the #14 (or #12) is somehow gaining Copper.

The Sixties end-of-small-gauge-branch-circuit fault current of 70 to 200 Amps is still what is available, today, in most cases, in my opinion.

I disagree that transformers are the same size. Most services in place in the sixties were 60 or 100 amps. Today is more likely 150 or 200. So...double. And in most cases even the cheapest PoCo's have at least kept up by increasing transformer capacity, as the average actual kWh usage is a higher percentage of service capacity than it was then...we tend to have and use far more electricity, even with LED's and Energy Star appliances and extended Daylight Savings time.

But either way, the undersized EGC's were at the lower end of marginally adequate then, and certainly haven't aged well.

 

[peter d]

But either way, the undersized EGC's were at the lower end of marginally adequate then, and certainly haven't aged well.

There's that. But it seems nobody is commenting on the fact that an EGC that size is no longer recognized by the NEC anyway. All new wiring has to meet to current code in force. It's a code violation to extend a circuit that relies on an EGC that is no longer deemed adequate.