Electric circuits in old houses--the Random Approach

Page 5 of 5  

snipped-for-privacy@gannon.edu wrote:

The connection does not have to get anywhere near hot enough to melt the lead to cause a problem, just moderate thermal cycling can cause the solder to begin to fail.

The biggest risk is simply that with the age of K&T the probability is very high that in those 100 years or so someone *has* hacked around with the wiring and/or over fused it.
Pete C.
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Pete C. wrote:

PC:
Right, because the thermal cycling causes expansion & contraction & stresses the joint. If it relies on solder, the solder will be stressed. My point is that house wiring isn't like a circuit board, where the solder is both the mechanical and electrical connection, but is simply a mechanical, twisted joint, covered in solder.

Agreed. Unfortunately, this is equally risky with old BX, old NM, or just about anything old. It's too bad that the insurers single out K&T, in particular, by virtue of visibility, exposed K&T, which is the safest kind, since it's well-cooled and easily viewed. Models and statistics are fine to protect the profits but only an individual consideration can protect the personal safety of the homeowner and his family.
Cordially yours: Gerard P.
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snipped-for-privacy@gannon.edu wrote:

Yes, the comparison of soldered wiring joints to electronics isn't very apt.
In a fairly quick search for actual data, I found none that statistically related the prevelance of fire to be any higher in K&T as compared to other forms--all data were simply reported as "fixed wiring" in the causation summaries and not broken out further.
Once analysis/review of the literature on causative factors in wiring-cause fires indicated the only real effect found with respect to K&T was owing to blanketing and the resulting induced temperature rise when the design limits of the insulation were consequently exceeded. Someone else noted about not being able to insulate walls w/ K&T and that is a valid limitation substantiated by that report. Oh, dang...I lost the link I intended to post--it was a pretty informative review. :( I'll try to find it again but don't have the time to do so right now...
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certinally 100 year old insulation can be detoriated.
its odd people who think nothing of buying new car after new car get upset that wiring wears out.
in a 100 years how many furnaces has the home had?
how many kitchen remodels?
how many new hot water tanks?
how many times has the carpet been replaced?
how many new roofs?
replaced your original water lines in a 100 years?
now why should wiring ne any different?
nearly all the items above cost many more times what new current code wiring costs....
yet people complain insurance doesnt like it.
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snipped-for-privacy@aol.com wrote:

Certainly insulation much less than 100 years old can be deteriorated, yes.
But, you seem to have misinterpreted my post. I'm not saying it shouldn't ever be replaced and I can't (and don't) really fault an insurance company for requiring it necessarily. OTOH, if an inspection shows it in good shape and undisturbed, there's nothing _inherently_ unsafe about it which seems to be the point others always want to make irregardless of any other factor. That's all...
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how does anyone inspect anything buried in a wall, most likely buried under flammable lath and plaster?
that wiring without grounds is way past its design life.......
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snipped-for-privacy@aol.com wrote: ...

So am I... :)
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Never the less, the system is as safe as it was when installed IF it hasn't been compromised or insulated around. The 286 computers will still do as well at word processing as they did the day they came out.
--
Steve Barker



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Amen!!
I still have my 286. Loved my amber monitor--was hi tech,back then! Loved Dos 3.3! :) -- Mr. P.V.'d (formerly Droll Troll), Yonkers, NY Stop Corruption in Congress & Send the Ultimate Message: Absolutely Vote, for *Anyone BUT* a Democrat or a Republican Ending Corruption in Congress is the Single Best Way to Materially Improve Your Life entropic3.14decay at optonline2.718 dot net; remove pi and e to reply--ie, all d'numbuhs

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Proctologically Violated wrote:

Started with a Commodore Vic20. Later onto a 386 with DOS 4.0 and Windows 3.0! Fell in love with the command line. Then Windows became all GUI's, then I found Linux. Now I can run as much or as little in the command line as I want. Been running Linux exclusively for last 6 years now.
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I did too. I wrote a lot of programs for that, and the later Commodore 64 & 128 machines.

I always feel that a command line lets you tell the computer what to do, and a GUI lets it tell you what it's willing to do. It's a matter of who's in control.
--
51 days until the winter solstice celebration

Mark Lloyd
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dpb wrote:

In a previoulsy posted link: http://www.waptac.org/sp.asp?idq90 a report to the Illinois Department of Commerce and Community Affairs didn't find a record of a hazard from insulation added around K&T wiring.
-- bud--
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Bud-- wrote:

OK, I had a chance to go look for the previous link again...it's here-- http://www.interfire.org/features/electric_wiring_faults.asp
Below is an excerpt on the insulation/overheating issue from it...this is the only occurrence of "knob" in the entire paper, but it is well worth reading imo...
I read the other paper as well but wasn't able quickly to find the reference cited in the following paragraph so what is lacking there is the information on how much external insulation was actually required to cause the overheating problem. IME it is likely for a "non-looped" run of wire not carrying over its rated ampacity to be far more than would be found in virtually any residential cavity for a structure of the age that would have K&T.
I wasn't arguing against, simply adding another piece of information and a link to a pretty informative paper, overall.
Here follows the section on K&T (which again doesn't say it is necessarily a problem, but that under certain circumstances _could be_ a problem)...
Excessive thermal insulation
There are simple ways in which a fire can be created with an electric cord that is neither damaged nor subjected to a current in excess of its rated capacity-loop it up upon itself several times, or provide a high amount of external insulation, or both. Laboratory demonstrations have verified that ignition readily occurs [ [28] ]; in one case, simply coiling the cord three times and covering with a cloth sufficed [ [29] ]. A special form of this hazard occurs with the old knob-and-tube wiring, which was common in the US prior to World War II. This type of wiring uses two separate conductors which are not grouped into a cable, but are individually strung on widely-spaced porcelain knobs. The current-carrying capacity is dependent on there being unobstructed air cooling of the wires, and fires have occurred when the wires were buried in thermal insulation [6]. .... [6] . Smith, L. E., and McCoskrie, D., What Causes Wiring Fires in Residences, Fire J. 84, 19-24, 69 (Jan/Feb 1990).
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My splices are twisted like I've never seen wire twisted, soldered, *wire nutted* AND taped!! Think there was a paranoid electrician at work?? Oh yeah, on plated wire! Cloth covering is *still* supple--thank gawd... -- Mr. P.V.'d (formerly Droll Troll), Yonkers, NY Stop Corruption in Congress & Send the Ultimate Message: Absolutely Vote, for *Anyone BUT* a Democrat or a Republican Ending Corruption in Congress is the Single Best Way to Materially Improve Your Life entropic3.14decay at optonline2.718 dot net; remove pi and e to reply--ie, all d'numbuhs

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Solder can detoriate over time, it grows crystals and changes.
insurance companies have stats to prove that K&T has more fires........
What other device do YOU have thats near 100 years old?:(
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