BX as a ground.

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Folks, thanks for the continued discussion of this aspect of the NEC. I am still, in this thread, endeavoring to constrain my comments to the Code itself. Opinion with Code citation is helpful.

"Grandfathering" is a challenging conversation, as we are experiencing. Armored Cable type BX (non-bonding strip) that was installed as a "system" has been required by Code to be grounded and has been a "grounding means" for at least a Century, as I have shown in the 1918 NEC quotes in an earlier post in this thread.

I am trying to understand how that status of being a grounding means is reversed to NOT being a grounding means by newer editions of the NEC.

A lot of weight, in this thread, is being given to whether grounding-type receptacle devices were used in type BX Armored Cable wiring method systems. . . . and, with this morning's coffee, I came to a thought about a parallel in real-world wiring in dwellings and occupancies.

Please consider a receptacle device replacement in an occupancy built in the early 1970s with Flexible Metal Conduit (FMC) as the primary wiring method. I live and work in a Metro Area of nearly 3 million souls. In it, there are tens of thousands of dwellings built since the 1962 NEC went into effect requiring ALL receptacle outlets to be of the grounding type, and before LOCAL ordinance, requiring ALL-METAL wiring methods only, was relaxed to also allow nonmetallic wiring methods.

Lets narrow this consideration to an early 1970s 120 Volt 15 Amp branch circuit wired to the Code of its original installation (early 1970s) wired with FMC (flexible metal conduit) and all associated metal fittings and boxes, with the actual wire being TW solid copper #14 gauge HOT and NEUTRAL only - (the FMC itself is the entire EGC per early 1970s NEC - there is NO equipment grounding #14 gauge copper wire inside the FMC).

To replace an existing duplex grounding-type receptacle device in an existing receptacle outlet in this early 1970s FMC branch circuit where only the FMC is the "existing grounding means", do YOU treat the FMC as an ungrounded wiring method?
 
al hildenbrand said:
I am trying to understand how that status of being a grounding means is reversed to NOT being a grounding means by newer editions of the NEC.
Click to expand...
From what I gather, it's simple and goes like this:

Experience showed that it was not an effective grounding means, and so the code was changed to no longer recognize it is as a grounding means. In particular, 320.100 was adopted at some point. At that point in time, all the installed BX cable without a bonding strap ceased to be AC cable, and its armor ceased to be a grounding means. There's no requirement to run around ripping it out, but if you touch it under a version of the NEC including 320.100, you can't use it as a grounding means.

Cheers, Wayne
 
Thanks, Wayne, but I suspect you might not have caught my question.
al hildenbrand said:
To replace an existing duplex grounding-type receptacle device in an existing receptacle outlet in this early 1970s FMC branch circuit where only the FMC is the "existing grounding means", do YOU treat the FMC as an ungrounded wiring method?
Click to expand...
Before you answer, follow 250.130(C), 406.4(D), 406.4(C), 250.118(5):
2014 NEC
250.118(5)
(5) Listed flexible metal conduit meeting all the following conditions:

a. The conduit is terminated in listed fittings.
b. The circuit conductors contained in the conduit are protected by overcurrent devices rated at 20 amperes or less.
c. The combined length of flexible metal conduit and flexible metallic tubing and liquidtight flexible metal conduit in the same ground-fault current path does not exceed 1.8 m (6 ft).
d. If used to connect equipment where flexibility is necessary to minimize the transmission of vibration from equipment or to provide flexibility for equipment that requires movement after installation, an equipment grounding conductor shall be installed.
Click to expand...
 
al hildenbrand said:
Folks, thanks for the continued discussion of this aspect of the NEC. I am still, in this thread, endeavoring to constrain my comments to the Code itself. Opinion with Code citation is helpful.
Click to expand...


If you wish to debate the intent of code itself this is perfectly fine, however given real world experience from many electricians I still do not believe that it ever be advocated having BX armor as an EGC. Even if the code does indeed remain mute it does not change the actual physics.


"Grandfathering" is a challenging conversation, as we are experiencing. Armored Cable type BX (non-bonding strip) that was installed as a "system" has been required by Code to be grounded and has been a "grounding means" for at least a Century, as I have shown in the 1918 NEC quotes in an earlier post in this thread.
Click to expand...


Can you show the older passages where the armor was listed as a grounding means?

I am trying to understand how that status of being a grounding means is reversed to NOT being a grounding means by newer editions of the NEC.
Click to expand...

IMO its just not recognized anymore. Perhaps not a perfect example, but the neutral is no longer listed as a grounding means for a clothes dryer or range.

A lot of weight, in this thread, is being given to whether grounding-type receptacle devices were used in type BX Armored Cable wiring method systems. . . . and, with this morning's coffee, I came to a thought about a parallel in real-world wiring in dwellings and occupancies.

Please consider a receptacle device replacement in an occupancy built in the early 1970s with Flexible Metal Conduit (FMC) as the primary wiring method. I live and work in a Metro Area of nearly 3 million souls. In it, there are tens of thousands of dwellings built since the 1962 NEC went into effect requiring ALL receptacle outlets to be of the grounding type, and before LOCAL ordinance, requiring ALL-METAL wiring methods only, was relaxed to also allow nonmetallic wiring methods.

Lets narrow this consideration to an early 1970s 120 Volt 15 Amp branch circuit wired to the Code of its original installation (early 1970s) wired with FMC (flexible metal conduit) and all associated metal fittings and boxes, with the actual wire being TW solid copper #14 gauge HOT and NEUTRAL only - (the FMC itself is the entire EGC per early 1970s NEC - there is NO equipment grounding #14 gauge copper wire inside the FMC).
Click to expand...

Well, I think you must ask. What is the difference between FMC and BX?


To replace an existing duplex grounding-type receptacle device in an existing receptacle outlet in this early 1970s FMC branch circuit where only the FMC is the "existing grounding means", do YOU treat the FMC as an ungrounded wiring method?
Click to expand...

My understanding is that code lets you use FMC as an EGC.
 
Here we go, I think this is key:


(5) Listed flexible metal conduit meeting all the following
conditions:
a. The conduit is terminated in listed fittings.
b. The circuit conductors contained in the conduit are
protected by overcurrent devices rated at 20 amperes
or less.
c. The combined length of flexible metal conduit and
flexible metallic tubing and liquidtight flexible
metal conduit in the same ground-fault current
path does not exceed 1.8 m (6 ft).
d. If used to connect equipment where flexibility is necessary
to minimize the transmission of vibration from
equipment or to provide flexibility for equipment that
requires movement after installation, an equipment
grounding conductor shall be installed.
Click to expand...
 
iwire said:
Al,

Imagine I have a 250' coil of new old stock BX.

Can I use it today to wire a house?
Click to expand...
Hi Bob,

No, one cannot use old stock BX as part of the wiring method material for the new installation of a new Premises Wiring (System).

Please, I'm trying to stay with the OP's question about receptacle replacement on EXISTING BX.

EXISTING FMC without internal added EGC (in lengths exceeding six feet) is affected by this "it's ungrounded" logic EXACTLY the same as old stock BX.
 
al hildenbrand said:
Hi Bob,

No, one cannot use old stock BX as part of the wiring method material for the new installation of a new Premises Wiring (System).

Please, I'm trying to stay with the OP's question about receptacle replacement on EXISTING BX.

EXISTING FMC without internal added EGC (in lengths exceeding six feet) is affected by this "it's ungrounded" logic EXACTLY the same as old stock BX.
Click to expand...

Al, you are telling me to stay on target when you just went off target with FMC.:)

My point is that if I can't use old BX for new work I also cannot extend off old BX for new outlets.
 
iwire said:
Al,

I do not believe that old FMC is listed at all and as such means the current 250.118 would not apply to it
Click to expand...

OK. If 250.118 doesn't include "old FMC" then "old FMC" is not NOW a "Type of Equipment Grounding Conductor" included in 250.118.

So you are saying, what, that if you approach a replacement of an existing early 1970s grounding-type receptacle device in a box on a branch circuit wired with "old FMC" containing no additional discreet ECG that you automatically treat the wiring method as UNGROUNDED?
 
iwire said:
My point is that if I can't use old BX for new work I also cannot extend off old BX for new outlets.
Click to expand...

I agree with your point Bob. If I am following 2014 NEC 250.130(C)(4) I will not find old BX included in 250.118.
 
al hildenbrand said:
So you are saying, what, that if you approach a replacement of an existing early 1970s grounding-type receptacle device in a box on a branch circuit wired with "old FMC" containing no additional discreet ECG that you automatically treat the wiring method as UNGROUNDED?
Click to expand...

Yes exactly that. Because it is not a presently recognized EGC.
 
al hildenbrand said:
OK. If 250.118 doesn't include "old FMC" then "old FMC" is not NOW a "Type of Equipment Grounding Conductor" included in 250.118.So you are saying, what, that if you approach a replacement of an existing early 1970s grounding-type receptacle device in a box on a branch circuit wired with "old FMC" containing no additional discreet ECG that you automatically treat the wiring method as UNGROUNDED?
Click to expand...
We don't have that problem here in residential as type NM cable has always been accepted. You will find lengths of the old FMC that are longer than 6 ft with no ground conductor in commercial. This was normally fished in walls and will only be a short distance (less than say 30 ft.) form a metal box attached to EMT ( and acceptable ground). Normally you would pull in a ground wire. I'm sure that many of these installations are missed because when you look into a junction box in a wall it's hard to tell if it's an EMT or FMC connector.
 
iwire said:
Yes exactly that. Because it is not a presently recognized EGC.
Click to expand...

So, in the existing grounding-type receptacle replacement on this old 1970s FMC, the probable low-cost fix is to replace the device with a GFCI receptacle labeled "No Equipment Ground". :?

How do you keep from bonding the device to the box?
 
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al hildenbrand said:
So, in the existing grounding-type receptacle replacement on this old 1970s FMC, the probable low-cost fix is to replace the device with a GFCI receptacle labeled "No Equipment Ground". :?

How do you keep from bonding the device to the box?
Click to expand...

I do not know what I would do in that situation that I would never find myself in as FMC was never used in this area for what you describe.

But OK, I would likely look into adding a wire EGC or leaving a two wire receptacle in place.

The fact that the situation you describe has difficult solutions does not change the fact old, unlisted FMC is not presently recognized as a grounding means.
 
iwire said:
I do not know what I would do in that situation that I would never find myself in as FMC was never used in this area for what you describe.

But OK, I would likely look into adding a wire EGC or leaving a two wire receptacle in place.

The fact that the situation you describe has difficult solutions does not change the fact old, unlisted FMC is not presently recognized as a grounding means.
Click to expand...
In a way, I'm lucky, I guess, in that my work area has such a diverse collection of wiring methods. There really are tens of thousands of single family dwellings here with almost every branch circuit completely wired with "old FMC". (And other parts of my work area that have a large installed base of Armored Cable Type AC and, in the older dwellings, Type BX.)

The routine replacement of that existing grounding-type receptacle is to install an OBC AFCI device, in most cases. . . and add a jumper from the box to the new device grounding terminal.

Here, the EXISTING EGC is seen as not "touched" by receptacle replacement, and is therefore still viable.
 
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