Effectiveness of 1920's armored cable ground

[wwhitney]

There you go again.

There I go, what? Asking you to detail your thinking?

I proposed a standard for adequacy, namely compliance with the 1941 mandatory UL standard for cable armor impedance. You've never responded to that.

If that's how you'd like to leave things, OK.

Cheers, Wayne

 

[big john]

...There is, today, no way to make 2014 NEC 250.118(8) apply only to one Armored Cable Type AC over another type of Armored Cable Type AC, in my opinion....

What do you believe the intent is of the description in 320.100 if not to do precisely that?

 

[iwire]

To be clear, I have stated numerous time in explanation of my position, that I am not advocating using non-bonding strip Type AC cable in new construction. I do, as previously stated, continue to state that connecting new wire to an unmodified existing Type AC cable's wires in an existing junction box is not new construction of the Type AC cable.

And that is the problem Al, that position makes absolutely no sense whatsoever.

 

[ActionDave]

...To be clear, I work in a Metro of 3 million souls, that has a HUGE installed base of dwellings and businesses that are wired partially, or completely, in non-bonding-strip Type AC armored cable, and I work on it almost every day. The Metro does not keep erupting in fire from this old cable. (Things that make you go, "Hmmm.")

That does not surprise me. There is tons of old and new wiring that would be considered dangerous, very little of which bursts into flame.

I am pushing back, here on this Forum, against the claims by others that "BX was never, and is not now, an EGC."

Didn't you say somewhere that we didn't even have equipment grounding until the 1950's?

 

[kwired]

Funny you mention raintight fittings, it was the example I originally thought of using.

I'm certain there are plenty of BX installs that will adequately clear a fault. But there seems to be evidence that some of them won't, and create a fire hazard in the process of trying, hence the amendment changing the description of AC to include a bond wire.

It makes me want to try and find a 75' piece of BX and see how it passes current on a test set.

I think certain OCPD's have lower magnetic trip that may play better with that situation then others, then if you use GFCI or AFCI (types with GF sensing in them) they would compliment such things pretty well, not saying any of that is required, but is worth consideration if still using an old cable.

Sure, but if you had to take to apart one of those fittings to rework a conduit run, would you reuse the old compression fitting, or use a new one that meets the updated standard? Ignoring for the moment whether or not the change was a joke, suppose it was justified.

Cheers, Wayne

I can't ignore the fact the change was a joke, the raceway will get more moisture inside because of condensation then it will ever leak, even if the compression nut isn't completely tight in many instances. They wanted to fix something that wasn't broke. I am not normally replacing said fittings unless there will be an inspector that makes me do it.

 

[ActionDave]

...I can't ignore the fact the change was a joke, the raceway will get more moisture inside because of condensation then it will ever leak, even if the compression nut isn't completely tight in many instances. They wanted to fix something that wasn't broke. I am not normally replacing said fittings unless there will be an inspector that makes me do it.

I agree. I hate those new rain-tite fittings and the fact that they accomplish nothing more than causing aggravation makes it hard to swallow that we have to use them.

 

[al hildenbrand]

What do you believe the intent is of the description in 320.100 if not to do precisely that?

Wayne has repeatedly asked the same thing. 250.118(8) only says 320.108.

320.100 is part of new construction.

 

[al hildenbrand]

And that is the problem Al, that position makes absolutely no sense whatsoever.

In your opinion, to you.

 

[al hildenbrand]

Didn't you say somewhere that we didn't even have equipment grounding until the 1950's?

Asked and answered many times and again to Wayne just back a few.

 

[kwired]

I agree. I hate those new rain-tite fittings and the fact that they accomplish nothing more than causing aggravation makes it hard to swallow that we have to use them.

I've always wanted to take a standard compression coupling and install it on a short piece of tubing and submerge the coupling in water for several hours and then see if any water makes it's way inside the tubing but have never gotten around to it. I sort of expect to see some water make it's way in, but one has to remember they never were and neither is the raintight ones listed for submerging AFAIK. Even threaded RMC/IMC will leak some at fittings unless you use some sealing compound on the threads, but NEC doesn't require us to use sealing compounds for water tightness reasons.

 

[big john]

Wayne has repeatedly asked the same thing. 250.118(8) only says 320.108.

320.100 is part of new construction.

Where does that distinction come from? 320.100 is the description you use when applying 320.108.

If BX doesn't match the specifications as described within the article, it seems to me that the logical conclusion is you can't apply that article to the wiring method.

 

[tkb]

Where does that distinction come from? 320.100 is the description you use when applying 320.108.

If BX doesn't match the specifications as described within the article, it seems to me that the logical conclusion is you can't apply that article to the wiring method.

There you go and applying logic to clear cut code references.

320.100, 320.104, 320.108 and 320.120 are all parts of the construction section of article 320. They all apply to AC cable. You can't just pick one.

 

[al hildenbrand]

320.100, 320.104, 320.108 and 320.120 are all parts of the construction section of article 320. They all apply to AC cable. You can't just pick one.

But, 250.118(8), being a general rule, is specifically pointed at only 320.108, allowing it a more general application to existing as well as new installations.

 

[peter d]

Peter, you do not use actual Code language in the bullet points, which I can. So your "opinion" that you are stating facts isn't yet really substantiated by the written language of the Code when it comes to the single key inflection point in your bullet point flow of logic below. That key inflection bullet point is what is contentious.

The problem is not my explanation. The problem is that you refuse to believe me, or even consider an opposing viewpoint.

I agree the construction standard was changed, as can be demonstrated by the changes in written language of the appropriate rule of the Armored Cable article through the 1950s into the early 1960s. I have not posted quotes of this "construction rule" from the NEC, but will be happy to do so if asked.

This is where you loose me, Peter. I can't find this in the 2014 or the 2011 NEC.

2011 & 2014 NEC 250.118(8) says (in toto), "Armor of Type AC cable as provided in 320.108". 320.100 is not invoked when describing the 250.118 Types of Equipment Grounding Conductors. I have shown in direct quotes and page scans of the old NECs, posted on this Forum several times, that armored cable, installed to the NEC of its original installation, has been Type AC since the 1913 NEC went into enforcement.

The designation "Type AC" in today's NEC does not give us a way to indicate that bonding strip armored cable is the ONLY Type AC allowed as an EGC, and that non-bonding strip armored cable is not allowed as an EGC. Rule 250.118(8) calls out ONLY the "armor", it does not say "armor and bonding strip" or some variation of words that get to the meaning of the AC construction rule 320.100.

A wise man once said "You can't convince a man of something that he has already determined that he doesn't want to believe." You squarely fit into the "doesn't want to believe" category. You are quite the wordsmith and I simply am not going to try to argue with you anymore. Do as you see fit because you mind is clearly not going to be changed. My hope is that others who read this this will not make the same mistake that you are making.

 

[big john]

But, 250.118(8), being a general rule, is specifically pointed at only 320.108, allowing it a more general application to existing as well as new installations.

What's the substantiation for that position? I'm asking sincerely, because I can't off-hand think of other situations where complying with one section of an article would appear to conflict with another section.

 

[tkb]

But, 250.118(8), being a general rule, is specifically pointed at only 320.108, allowing it a more general application to existing as well as new installations.

Since 250.118(8) is about grounding, of course it is going to reference 320.108, and since 320.108 is part of the construction section of 320 all parts of section III of 320 apply.

 

[user 100]

thank you for the reply. as for what needs a ground, that's a whole different topic.

eta: the wire insulation(TW?) in that old AC seems to be more problematic than a ground path. Maybe it's just been my luck, but more times than not the insulation has disintegrated to the point of needing replacement.

That's probably going to be cloth coated or plain rw (rubber) for bx made prior to the mid '50s and tw for stuff later on. Tw will deteriorate some at fixures, but aged rw that has been exposed to only air (think rubber oxidation) will at times just crumble- but you can often trim the jacket back and the insulation will still be in decent or even excellent shape, most of the time.

The older bx is unlike any other older wiring method- the potential problems that can occur are fairly unique- you will often have guaranteed high impedance due to a rusty steel jacket that is enveloping conductors w/ failing dried out insulation at the least at junctions or even in untouched lengths of bx that haven't aged so well- just manipulating the cable a little can cause problems.

Many electricians just don't like messing w/it. A lot of installations (certainly not all, but many) are a big enough risk already due to aforementioned factors w/out attempting to use the armor as an egc.

 

[al hildenbrand]

The problem is not my explanation. The problem is that you refuse to believe me, or even consider an opposing viewpoint.

Personal character attack is a logic fallacy.

You are quite the wordsmith and I simply am not going to try to argue with you anymore.

I am hardly a wordsmith when I am using the unaltered words quoted from the NEC, NFPA documents and from UL and its representatives.

 

[user 100]

Remember, 406.4(D)(1), in addition to using "grounding means" also includes "equipment grounding conductor."


Once one gets to seeing that the 2014 NEC 250.118(8) says that all "Type AC cable" has armor that is an EGC, then 406.4(D)(1) falls into place as inescapable.

But what exactly is "grounding means"? They never specify what that is- it's almost like the code bosses threw that in there for their amusement just to watch a bunch of guys argue about it's exact verbiage on some electrical forum.

What they may mean by that phrase "grounding means exists" is wiring that already has an egc and the second part that specifically mentions the term egc is referencing an egc that has been added per 250.130. Basically covering their bases to make it clear that when one replaces a receptacle on wiring that already has an egc or wiring that has had an egc added via 250 exception for nongrounded bc ext's, it must be connected to an egc per 406.4(C) or 250.130(C).

 

[JFletcher]

That's probably going to be cloth coated or plain rw (rubber) for bx made prior to the mid '50s and tw for stuff later on. Tw will deteriorate some at fixures, but aged rw that has been exposed to only air (think rubber oxidation) will at times just crumble- but you can often trim the jacket back and the insulation will still be in decent or even excellent shape, most of the time.

The older bx is unlike any other older wiring method- the potential problems that can occur are fairly unique- you will often have guaranteed high impedance due to a rusty steel jacket that is enveloping conductors w/ failing dried out insulation at the least at junctions or even in untouched lengths of bx that haven't aged so well- just manipulating the cable a little can cause problems.

Many electricians just don't like messing w/it. A lot of installations (certainly not all, but many) are a big enough risk already due to aforementioned factors w/out attempting to use the armor as an egc.

Yep, and I imagine TX and VA have similar conditions, tho humidity and freezing here might affect outside fixtures more. I admit Im one who doesnt like the stuff.

Al and all, wouldnt be a simple enough proposition to take each case of old AC on its own? How hard would it be to measure resistance to panel? If I got 0.7 ohms (say j-box AC 20' from the panel), it would be an acceptable EGC, but if you get 4 or 13.72 ohms, it's not? (based on 1.5 ohm standard). Is this too much work, or liability for the EC? or am I missing the point entirely; Old AC; acceptable ground or not?

eta: there has to be someone with a definitive answer to this question; does MH have any videos r: this topic?