Is old BX "safe" or not?

Reply to
Phil Munro
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I'm sorry, I took (and have taken over the years) it to mean, "Hey, you dumb Americans. Wake up and learn what we Canadians, the smartest people in the world when it comes to electrical codes, mandate for our electrical installations. Just follow our lead and you'll be alright; second-best maybe but OK."

I only know of one thing the Canadians have to teach us and that's how to set up a single payer health care system but then again most countries of the developed world, probably even Bulgaria, could teach us something about health care systems.

Igloo construction too, perhaps .

Reply to
SpamFree

That entire interpretation was silly when you consider I had also posted a long discussion on how Canada is slowly adopting American style rules for GFCIs in kitchens.

As Terry suggests, it was merely given as an example of an equally competent electrical authority having reasons for and choosing not to go the "use armor as ground" route.

The US govt. and construction industry is rather fond of our R2000 construction methodology and quote/reference it a lot.

But they're not igloos.

Reply to
Chris Lewis

According to SpamFree :

Yup. Here too.

But of only minimal use as a ground. Those outlets were two prongs.

Just how good do you think 50 year old BX armor is as a ground, given the oxidation it, the boxes, and clamps have gotten over the years?

And it's proposed to utilize this as a classic three prong outlet grounding system. I've seen too much of that stuff to trust it.

Like the perfectly well panel-grounded chunk of BX in my friend's basement that recently raised an enormous bang when a contractor slung a grounded metal trouble light on it. You see, the end had a hot-armor short, and the armor didn't have enough conductivity to trip the breaker.

Contractor: "we see this all the time...".

The house is about 100 years old.

It happens. My co-author has seen it. And, IIRC, it was the cause of the major casino fire in Vegas.

No. Very few jurisdictions, if _any_, are requiring mandatory replacement of K&T, except in renovation work to new code. It's the insurance companies in the private sector making K&T difficult to insure. Despite the fact that aside from burial in insulation, existing K&T is usually quite safe. Better than some later wiring systems.

Similarly aluminum. Proven track record of hazard. Is there a mandatory recall? No.

Asbestos.

UFFI.

Lead paint.

PT lumber.

Etc. Except for few cases (mostly commercial or local rules), none of these are required to be removed. Mitigated in many cases, but rarely mandatory removal.

You can argue that they're not as hazardous as some claim all you want, but, they have been deemed hazardous, and _none_ of them are subject to mandatory complete removal. Because it costs too much.

Bus bars and terminal tabs aren't steel either, they don't have to be bent at all. Steel isn't suitable for that use either. Steel simply isn't suitable as a conductor (except perhaps conduit, and even that we don't permit).

[Canadian code, and I suspect US too, even doesn't really permit you to use a metal box as part of a ground conduction path - you gotta bond those copper ground wires together in NM, rather than run them under different box screws. Except with US AC...]
Reply to
Chris Lewis

Last summer I found out that a local restaurant was going to be demolished. They were having problems finding a place to dispose of the lumber, and because of some new law, they can no longer burn buildings that (might) contain asbestos, lead, and other scarey stuff that modern science has determined to cause cancer and a million other horrors that we are supposed to fear if we eat our homes and businesses.. Well, I really do not find buildings something that I would want to eat, so I am not worried about this stuff.

Anyhow, I offerred to tear the place down as long as I got all the lumber. They were pleased, and so was I. Now, I normally save all electrical stuff that is still usable, so I pulled down all the fixtures and the breaker box before I took off the roof. I generally save the wire, but only to sell for copper. So, all I reapply planned to take was the junk wire and the metal boxes to reuse. Much to my surprise, when I opened the roof, I saw that all the modern NM (romex) had the outer coating removed across most of the attic. At first I thought they had hired an insane electrician, until I saw further down the way, where some spots actually had both insulated conductors stripped right down to bare copper, often for several feet in a row. That's when I realized that mice had caused that. It's amazing that these wires never touched, but I did find a couple mouse skeletons directly next to these wires, so I assume they were electricuted. All of this cable was the modern style, not the old cloth covered stuff. Over in the older part of the building, there was BX. None of that had any damage. After seeing that, I will never use NM cable in a enclosed wall or ceiling. I will use it, for example, in my garage, where its all exposed, but if I were to ever build myself a new home, it would be all AC, greenfield, or steel conduit. Those wires were uninsulated for 10 feet in some spots, with only bits and pieces of the insulation remaining. If someone had gone in the attic, they could have been electricuted. The mouse could have started on fire and burned the whole place.

I think this answers which is better !!!

Mark

On Mon, 17 Jan 2005 19:43:13 -0500, "RBM" wrote:

Reply to
maradcliff

Intersting...... I never knew where the names BX and Romex came from...

The ideal solution is to use greenfield. Use a black, white and green wire. On a flat surface, such as a basement ceiling, use steel conduit.

I did actually see some of the old BX (without grounding conductor) start a fire. I used to do handyman work and had a guy call me one evening, insisting I come immediately because his lights were going on and off and getting dimmer. When I got there I smelled smoke. When I got to the old fuse box in the basement I felt a very hot BX cable (#14 wire) with a 30A fuse. I shut off the power, called the fire dept, and busted a hole in the wall right above the box. The BX was very hot, and had charred the wood, but not yet caused flame. Another hour, maybe less, that place would have burned. The AC cable, eliminated that problem pretty much. While I understand the resistance issue, I never could totally understand how a spiral would cause the resistance, since it was still a continuous piece of steel. However, I DID see the result.

Needless to say, that place needed complete rewiring.

Yes, it is STILL called BX in the stores.

Reply to
maradcliff

According to :

Out of curiousity, "modern" in the sense of being more modern than old BX, or "modern" in the sense of being recently manufactured NM?

I've seen this (right down to the bare wire in places) too.

It was wiring within the eaves of an old house. The roof structure (esp soffits) was heavily damaged. We assumed Racoons at the time. Could have been mice.

[No skeletons, the soffits were that badly "not there"]

It was NM all right, but not the stuff we've been using in the past

20-30 years with thermoplastic sheath. It was the stuff from the 40's/50's with a varnished cloth/fiber exterior sheath.

Much more appetizing to varmints than PVC, especially if the varnish had a salty taste.

In sofar as being chewed on by mice. On the other hand, if you were using ground-less BX and relying on the armor sheath for grounding, having those mice pee on the cable (they pee on _everything_) means you have poor/no ground in very short order and a wiring fault will result in a fire or potential electrocution.

Nothing's perfect :-(

I like TECK cable most of all. Armored cable with thermoplastic exterior sheath, and a real ground conductor. It's what's used in hostile environments like mineshafts, and for outdoor events, like concerts or by mobile carnival ride companies where large quantities of people and vehicles will be running over it.

But TECK is real expensive.

Reply to
Chris Lewis

I meant modern in the sense of being the stuff currently being used, not the old cloth covered non grounded stuff. That part of the building was renovated about 8 years ago.

Reply to
maradcliff

sounds like that was simply a case of the wrong fuse and wasn't the fault of the spiral armor, the wires inside the armor were getting hot.

I think the worst electrical saftey issue I have seen (I live in the US) is older 220V dryers. They are plugged in via a big 3 prong plug. Two of the prongs are 220 and the third prong is a COMBINATION return and saftey ground!!!. In my dreyer, the heating coils are across the

220 pongs. But the 110 volt motor and clock are connected from one 220 pin to the combination return / ground pin which also connects to the chassis.

SO...if this retun line should fail OPEN someplace, there will be 110V on the dreyer chassis (through the motor). And of course the dreyer sits right next to the washer which is grounded by it's regular 110v outlet. so by a simple open failure, there can be 110V ac across my washer and dreyer. I see the cat walk across there all the time not to mention the wife and kids. I was so concerned about this, that I added a hard WIRE between the washer and dreyer chassis.

I think all newer dreyers have a 4 prong plug where the return and saftey ground are seperate. But it boggles my mind that any saftey organization would have ever alllowed the older three prong system. Mark

Reply to
Mark

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