BX as a ground.

[iwire]

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

Strip the NM, take the EGC and wrap it around the NM, now put it in a metal NM clamp so that when you clamp the NM you squeeze the EGC as well.

This was even taught in the trade schools around here in the 60s. (My older brother went to trade school 67-69)

 

[JFletcher]

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?

Couldnt one just cut and connect a test wire (say,#12 stranded) wire from the panel ground bar, measure it, check its impedance, run it back to the test point (say an outlet box where the receptacle is), and measure total impedance across new wire and old BX armor, subtract the impedance from the new wire to get the impedance value of the BX armor?

Also, if there were a fault to high resistance ground, but not enough to trip the OCPD, wouldnt an IR camera be able to see this in the walls?

 

[iwire]

before you nit pick me, how much BX do you work with

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

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.

 

[wwhitney]

250.4(A)(5) used to be '2551' 50 years ago

it reads>

Effective Grounding. The path to ground from circuits, equipment, or conductor enclosures shall be permanent and continuous and shall have ample carrying capacity to conduct safely and currents liable to be imposed on it, and shall have impedance sufficiently low to limit the potential above ground ,and to facilitate the operation of the overcurrent devices in the circuit.

The adoption of this code language rendered all "old style" BX ungrounded from that point in time forward. It doesn't matter if earlier versions of the NEC considered the circuits grounded, the above language clearly means they are ungrounded according to any NEC version that includes it.

So for a receptacle replacement under a current version of the NEC, the "old style" BX is ungrounded, and the rules for receptacle replacement on ungrounded circuits apply.

Cheers, Wayne

 

[GerryB]

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?

 

[al hildenbrand]

Also, 406.4(D) was cited. Consider:

2014 NEC
406.4(D)(1) Grounding-Type Receptacles. Where a grounding means exists in the receptacle enclosure or an equipment grounding conductor is installed in accordance with 250.130(C), grounding-type receptacles shall be used and shall be connected to the equipment grounding conductor in accordance with 406.4(C) or 250.130(C).

We can't use the rule 250.130(C) because it is limited to ungrounded wiring methods. So let's go to 406.4(C):

2014 NEC
406.4(C) Methods of Grounding. The equipment grounding conductor contacts of receptacles and cord connectors shall be grounded by connection to the equipment grounding conductor of the circuit supplying the receptacle or cord connector.
(info note about electrical noise)
The branch-circuit wiring method shall include or provide an equipment grounding conductor to which the equipment grounding conductor contacts of the receptacle or cord connector are connected.
(info note #1: See 250.118 for acceptable grounding means.)
(info note #2: leads to 250.130 which doesn't apply)

So, going to 250.118, let's go straight to 250.118(8):

2014 NEC
250.118 Types of Equipment Grounding Conductors.

(8) Armor of Type AC cable as provided in 320.108.

Period. That is ALL (8) contains. I'm not omitting anything.

So, going to 320.108:

2014 NEC
320.108 Equipment Grounding Conductor. Type AC cable shall provide an adequate path for fault current as required by 250.4(A)(5) or (B)(4) to act as an equipment grounding conductor.

And we seem to be in a cul-de-sac that has no other meaning. But I submit that there is a single clear fork in the trail that was missed back in 406.4(D)(1).

Now, please, bear with me. As I have said from the beginning, the difficulty, in our discussion here in this thread, is the assumption that AC type BX is ungrounded. To follow my logic, my reading of the Holy Writ, allow that type BX is grandfathered as an "existing grounding means" and keep that in mind to the bottom of this post.

406.4(D)(1) contains two very different things: 1) a receptacle enclosure with an EXISTING grounding means; or 2) the INSTALLATION of an EGC by 250.130(C).

No new EGC (in the wiring method) is going to be installed so 250.130(C) doesn't apply as it is limited in the first paragraph of 250.130 to ungrounded wiring methods (please, bear with me).

So we go to 406.4(C) and the first sentence tells us to bond from the receptacle device to the EGC of the supplying circuit. Looking at the related Informational Note we see noise reduction guidance.

At this point, and this is the heart of my position, NOTHING is said that defines the nature of the "existing grounding means." That information is in SEPARATE informational notes that append to the second sentence of 406.4(C). Observe that the numbering of the informational notes RESTARTS after the second sentence.

In a receptacle replacement in a box supplied by AC type BX, no new branch-circuit wiring is installed . . . and that is what the second sentence of 406.4(C) is about, a newly installed branch-circuit wiring method. So the second sentence doesn't come into play, and we never get to the informational notes for the second sentence.

Thank you for bearing with me as you read this. I maintain that the Code is silent about an existing wired to the Code of its original install AC type BX cable as a grounding means, which means the EGC is still there.

 

[romex jockey]

This is nearly century old Code. You are offering your opinion that the new construction standard of the 2014 NEC retroactively eliminated the grounding means that AC type BX cable has ALWAYS been. Show it in the text of the NEC.

Mr Al

While i appreciate any vintage NEC passage, and really hate to introduce trade semantics , groundED and groundING have two distinct meanings, and one did not exist in '18 branch circuitry.....

~RJ~

 

[al hildenbrand]

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?

You've captured the question. It is what is being discussed.

 

[al hildenbrand]

Mr Al

While i appreciate any vintage NEC passage, and really hate to introduce trade semantics , groundED and groundING have two distinct meanings, and one did not exist in '18 branch circuitry.....

~RJ~

Yes. The language is in an earlier stage of use. It makes it a little more challenging to read, trying to not apply the 2014 filter of definitions.

The 1918 NEC passages use BOTH groundED and groundING. . .

 

[romex jockey]

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?

BX differs from AC in the bonding strip.

BX has no bonding strip

The entire reason for the bonding strip is to allow the jacket to be an egc

no strip, no egc

~RJ~

 

[al hildenbrand]

no strip, no egc

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.

 

[romex jockey]

Yes. The language is in an earlier stage of use. It makes it a little more challenging to read, trying to not apply the 2014 filter of definitions.

The 1918 NEC passages use BOTH groundED and groundING. . .

IMHO, they are talking about making the BX to the MBJ, not utilizing it as a EGC Al....

When the service conduit is grounded, its ground conductor must be run direct from it to the ground connection. The interior conduit, armored cable or metal raceways, if well bonded to the service conduit, grounded as provided in this rule, need no additional connection.

~RJ~

 

[romex jockey]

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.

I say we file for a formal interpretation then Al

~RJ~

 

[al hildenbrand]

IMHO, they are talking about making the BX to the MBJ, not utilizing it as a EGC Al....

Note the heading "Equipment and Wire Raceways". "i" through "n" are all under that heading. The language relating to the main bonding jumper is elsewhere.

 

[wwhitney]

We can't use the rule 250.130(C) because it is limited to ungrounded wiring methods.

Old style BX cable without a bonding strip is not a grounded wiring method under the 2011 NEC (see below), so 250.130(C) is appropriate.

So, going to 250.118, let's go straight to 250.118(8):

(8) Armor of Type AC cable as provided in 320.108.

Great. But BX cable without a bonding strip is not AC cable per 2011 NEC 320.100:

320.100 Construction. Type AC cable shall have an armor of flexible metal tape and shall have an internal bonding strip of copper or aluminum in intimate contact with the armor for its entire length

If there's no bonding strip, then it's not AC. The definition of AC cable in 320.2 directly incorporates 320.100.

As I have said from the beginning, the difficulty, in our discussion here in this thread, is the assumption that AC type BX is ungrounded.

Indeed, as I just demonstrated. None of the acceptable grounding means listed in 250.118 apply to type BX without a bonding strip.

At this point, and this is the heart of my position, NOTHING is said that defines the nature of the "existing grounding means."

OK. But I think it is fair to say that it must be a grounding means as enumerated in 250.118.

Cheers, Wayne

 

[George Stolz]

Thank you, Netpog, for quoting the Code, instead of just giving opinion.

As I have said from the start, with direct citations quoted from the NEC (referenced by clicking on this thread link) :

In using 250.130(C) to substantiate your claim, you have overlooked the first part of that Rule:

Quoting today's definition of EGC, and failing earlier editions of the NEC that don't use it, is a non-starter. Earlier editions of the NEC clearly state that Armored Cable type BX is a grounding means, just not in today's words.

Federal Pacific breakers are also listed products by that reasoning. I think your reasoning is unsound.

 

[al hildenbrand]

Old style BX cable without a bonding strip is not a grounded wiring method under the 2011 NEC (see below), so 250.130(C) is appropriate.


Great. But BX cable without a bonding strip is not AC cable per 2011 NEC 320.100:


If there's no bonding strip, then it's not AC. The definition of AC cable in 320.2 directly incorporates 320.100.


Indeed, as I just demonstrated. None of the acceptable grounding means listed in 250.118 apply to type BX without a bonding strip.


OK. But I think it is fair to say that it must be a grounding means as enumerated in 250.118.

Cheers, Wayne

Wayne, you are copying my copy of the argument against me. Please read the second half of my post.

 

[al hildenbrand]

Federal Pacific breakers are also listed products by that reasoning. I think your reasoning is unsound.

OK. But I'm only talking about receptacle replacement on an existing AC type BX branch-circuit installed as a grounding means under the Code of its day.

Please give the second half of this post a read if you can give it the time.

 

[wwhitney]

In a receptacle replacement in a box supplied by AC type BX, no new branch-circuit wiring is installed . . . and that is what the second sentence of 406.4(C) is about, a newly installed branch-circuit wiring method. So the second sentence doesn't come into play, and we never get to the informational notes for the second sentence.

Not at all true. The second sentence of 406.4(C) (2011) reads:

The branch-circuit wiring method shall include or provide an equipment grounding conductor to which the equipment grounding conductor contacts of the receptacle or cord connector are connected.

This is a limitation on the type of branch-circuit wiring to which one may install a grounding-type receptacle. There is nothing in this sentence to suggest it applies only to new wiring that is installed. In fact, this sentence is a direct prohibition on installing a grounding-type receptacle on BX cable without a bonding conductor, as such wiring violates the requirement, as it has no EGC.

Cheers, Wayne

 

[user 100]

Federal Pacific breakers are also listed products by that reasoning. I think your reasoning is unsound.

:thumbsup:. By connecting 5-15 receptacles to the old bx and attempting to use the casing as an egc, you are essentially using a product outside of it's listing/use and/or no longer recognized- I think this would negate any grandfathering arguments. The deal here is that you're not installing grounding type recs in the 1940s when that product might have had it's listing- you're only installing 5-15's and simply using something not recognized by today's NEC for an egc.