BX as a ground.

[ActionDave]

Could someone answer a question for me. Action Dave said in the first post to the op if the bx had no bond strip it couldn't be used for a ground. Is that right? I have done hundreds of jobs, service changes, etc, where there was no bond strip in the bx. You strip some it has paper to peel off. Some has waxed cloth to get off. No inspector (and some very knowledgeable) has ever questioned or mentioned the age or acceptability of this bx.
Am I missing something?
Is there bx after the 1960 date with no bond strip that is ok?
Are some saying all these systems should considered ungrounded?

Yes, that is what I said. The code references were to point out ways one could put in three wire recpts without replacing the existing wiring. Alternately one could use two wire recpts.

Nobody is arguing that old BX has to be ripped out, just whether or not the sheathe is an acceptable EGC. Al is as sharp as anybody on this forum. Most of the time I agree with him. In this case I do not.

Type AC cable since 1960 something includes the bonding strip that makes the sheathe suitable for an EGC.

 

[user 100]

No inspector (and some very knowledgeable) has ever questioned or mentioned the age or acceptability of this bx.

Remember too that those third parties often have no real skin (like ultimate liability) in the game and/or aren't aware of the issues that could very well occur with a high impedance fault and the pre bond wire old bx.

 

[mbrooke]

Q. E. D.
Tapatalk

???

 

[mbrooke]

As I said earlier, it's easier to dig in one's heels than admit to a major mistake.

I agree. That seems to be the case here. Its the only logical explanation.

 

[mbrooke]

How about this:

When the cable was shiny new, the armor had a low impedance back to the panel, so OK to use as an EGC. Aging effects changed that and weren't noticed for years. The bonding strip was then required to circumvent those aging effects.

Good possibility, but Al refuses to believe this based on what old thinking said.

 

[peter d]

So your saying meters are just giving opinions? :lol:


But again, before you nit pick me, how much BX do you work with and how do you perform an ground loop impedance test?

No doubt in my mind he works with it a lot. But that doesn't absolve him from being very, very wrong on this issue.

 

[mbrooke]

There! That wasn't so hard. The Code is SILENT on the matter.

Its not silent, it openly says its not a recognized method.

 

[mbrooke]

How ironic, when I ask you questions like this, ones that you refuse to answer, you get offended.

What questions have I refused to answer? I have answered everything to the best of my limited knowledge.

I will add that while I don't always agree with Al I have never once doubted he has extensive hands on experience installing electrical equipment and dealing with old installations.

Extensive to the point Al claims he tests the impedance of BX cable yet he refuses to answer. I can only concluded he does not...

 

[mbrooke]

I agree for new installations of Armored Cable. I disagree for existing installation of AC type BX without a bonding strip that was installed as a system of interconnected parts . . . I am maintaining that the original use as a grounding means is maintained even today under the 2014 NEC.

Its clear you have never tested the grounding impedance of BX cable and assumed all along it was an adequate EGC. Anyone with the raw numbers would know the armor will not function as an EGC no matter how the code is interpreted to support a myth.

 

[mbrooke]

No doubt in my mind he works with it a lot. But that doesn't absolve him from being very, very wrong on this issue.

And perhaps he does as you know him better then I, (its impossible to say who does what over the net) but refusing to answer a basic question makes me doubt where he is coming from.

 

[ActionDave]

And perhaps he does as you know him better then I, (its impossible to say who does what over the net) but refusing to answer a basic question makes me doubt where he is coming from.

Maybe you would like to answer the basic question about when or where you worked as an electrician?

 

[mbrooke]

Maybe you would like to answer the basic question about when or where you worked as an electrician?

In a family business roping houses and doing service calls.


But again, I could question others even more if this is the culture of the forum... If Al is doing loop impedance testing on BX he can certainly provide numbers.

 

[mbrooke]

But, asking again since this can settle the adequacy of unbounded armor as an EGC and back up your claim:

Now, I, as a field electrician, facing a receptacle outlet that needs its device replaced, can TEST the resistance of the EGC to determine if there is an issue.

1. How do you test this? (tools, method, ect)

2. Is it routine for you? (done every-time BX is encountered)

3. If not, what makes you question the grounding (bonding) integrity of the circuit to conduct such a test?

4. What numbers do you get when testing is done?

 

[ActionDave]

But again, I could question others even more if this is the culture of the forum...

Or you can stop questioning Al's aptitude as an electrician or his experience working on old wiring.

If Al is doing loop impedance testing on BX he can certainly provide numbers.

I don't think that has anything to do with his position he is taking in this thread.

 

[mbrooke]

Or you can stop questioning Al's aptitude as an electrician or his experience working on old wiring.

As Iwire and other members can stop questioning mine :thumbsup:

I don't think that has anything to do with his position he is taking in this thread.

If he has seen actual numbers that can support his claims that BX is an adequate EGC.

 

[user 100]

Couldn't you remain compliant by replacing the receptacles with NEMA-1 devices?

Good luck finding TR ones. (In other words, maybe my above suggestion isn't helpful.)

No, it's fine

TR doesn't apply to 2 wire recs for replacement use:

406.12 exception (4)
"Nongrounding receptacles used for replacements as permitted in 406.4(D)(2)(a)"

 

[Fulthrotl]

If he has seen actual numbers that can support his claims that BX is an adequate EGC.

ok, i'm new here, but i have a thought that i'm sure has been expressed
somewhere waaay back there <--------- but let me see if i understand correctly:

BX was a wiring method used BEFORE grounded outlets were in common use, correct?
so, irregardless of the reason, it was not an issue when the product was in common usage, right?
as there were no grounded devices to make use of a grounding path. correct?

once grounded receptacles were common, there was a bond wire, and it became AC, correct?

now, if you have a spiral coil of metal that is pushing 100 years old, and corroded, you will end
up with a spiral steel ground path encircling the conductors. connectivity will be reduced in a direct
path up the spiral, and will instead be a circular path, resembling a choke, of sorts.

there are a lot of variables here. so, setting aside the code entirely, if you were going thru
a house changing out devices to 3 wire, and you connected a coil of #14 thhn stranded to
the building ground, and with the power turned off to the house, used a digital ohm meter
to measure each box to the service ground, and ALL of them were less than 3 ohms, which
is the current standard applied to ground resistance on new construction, could we then
move on to really important things, like should the ground pin be up, or down?

 

[user 100]

In other news, I'm surprised to report that this page will be your only google hit on the phrase "cromulent EGC".

This is actually true.:lol:

 

[mbrooke]

ok, i'm new here, but i have a thought that i'm sure has been expressed
somewhere waaay back there <--------- but let me see if i understand correctly:

BX was a wiring method used BEFORE grounded outlets were in common use, correct?

Correct.

so, irregardless of the reason, it was not an issue when the product was in common usage, right?
as there were no grounded devices to make use of a grounding path. correct?

Correct. Although, just throwing an observation into the pool, the boxes on BX are metal (the ones Ive seen), so its possible for a live to short to the case.

once grounded receptacles were common, there was a bond wire, and it became AC, correct?

Probably. I need to confirm and double check the dates. Anyone how could do the same would be of even more value as I dont have old code books on hand.

now, if you have a spiral coil of metal that is pushing 100 years old, and corroded, you will end
up with a spiral steel ground path encircling the conductors. connectivity will be reduced in a direct
path up the spiral, and will instead be a circular path, resembling a choke, of sorts.

Correct, this is the theory at hand.

there are a lot of variables here. so, setting aside the code entirely, if you were going thru
a house changing out devices to 3 wire, and you connected a coil of #14 thhn stranded to
the building ground, and with the power turned off to the house, used a digital ohm meter
to measure each box to the service ground, and ALL of them were less than 3 ohms, which
is the current standard applied to ground resistance on new construction, could we then
move on to really important things, like should the ground pin be up, or down?

What is this 3 ohm standard sited? (just wondering).

If in all cases the impedance is low BX used as a ground will not be an issue.

As for ground up ground down is a preference, however when metal plates are involved ground up has an advantage.

 

[mbrooke]

I volunteer to be the dumb one. What is "Boston Back wrap"?

Came can seen here to the right (cloth NM)

https://www.youtube.com/watch?v=tL-kxEVgLUw