This is a link to a study done by NFPA & UL on aged wiring in the US. A long report but worth the time to read it.

http://www.nfpa.org/assets/files/PDF/Research/RESAReport.pdf

Lucky:
Thanks for the link!

I seem to remember seeing this, or something similsr recently, but ?? where.

Reno....ring any bells???

Sure does ... some time ago I posted a thread on this topic, after having peeked at some preliminary findings.

The final report is sure to be an interesting read. If nothing else ... like good engineers, the examiners assumed that the bulk of the problems found would be due to either simpler codes, or aged equipment.

Naturally, as any conrtractor might have told them, the vast majority of the problems arose from later attempts by unqualified folks to "improve" upon the dated system.

To illustrate the point ... my own home was built in 1940. The kitchen has but one (single) receptacle, while the living room has a half-switched duplex. The service was also lacking a ground rod, and there are no ground wires in the original Romex. I think we can see how most such homes have, by now, had several 'handyman' improvements made over the years.

I've only just skimmed the report, but there's a lot of interesting data there.

Be sure to take a look at the early 20th century receptacle shown in Figure 19 on pdf page 47 (report page 38). Now that's a beauty!

The unqualified/hacks/handymen probably are not mentioned within the report.

I downloaded it to read; time permitting

Check out the last 2 pages, John, you'll be unpleasantly surprised.

Note that they were not able to tell the difference between unknowledgable professionals and simple DIY hacks. But when the house burns down, is there really a difference?

Oh, I have, Steve. There are more 'could' and 'possibly' qualified statements than actual conclusions there!

Absent from the summary is that there simply wasn't such a thing as 'outdoor' equipment for much of the period under study. For example, I have yet to see a fuse box that would pass today's NEMA-3R test; I wonder just when such tests (there were different UL and NEMA standards until quite recenlty) were codified.

The vast bulk of the hazards were the sort of things we feature here, in our photo sections. In other words, we're not talking about the lack of bubble covers, AFCI's, or making extension cords out of 4-squares. It's our "usual suspects:" over-fusing, double-lugging, over-lamping, lamp cord as permanent wiring, flying splices, 3-prong receptacles on ungrounded systems, etc.

In contrast, there's little evidence of components failing simply because of age- and little evedince to support the bulk of code changes (or additions) in our lifetime. The report fails to address the electrocution and fire statistics that it presents; that is, we have no idea what share of these losses would have been avoided had only the (say) 1940 NEC been followed.

I want to contrast this to the attitudes espoused - most vocally - by the 'home improvement' crowd. The dangers lay not in whether the house has fuses or FPE breakers ... but, rather, in that extension cord cobbled on to the knob & tube, and the 30 amp fuse feeding the #14 to the overlamped lights.

The study showed that many of the conductors had deteriorated, though. Electrical resistances were about twice what is allowed for that grade of wire. And every single breaker failed to trip when tested. Those are issues, too.

There were many age-related things due to evolving codes and standards, as well. Things like having a single 15A non-GFCI receptacle in a kitchen would send an inspector into a fury, but there are thousands of people out there who live like that, and it's dangerous. The law might not require them to upgrade, but their homeowner's insurance company sure takes it into account.

Unless I've missed something, it was 5 out of 421 breakers that failed. And those were mostly ones that were exposed to poor environments, like being in outdoor mounted boxes and such, and had insect intrusions and corrosion.

The old BX cable that has twice the permitted resistance in its armor is a bit worrisome. My mom's house has some runs of BX without the bonding strip, but they are short enough to keep the total resistance low enough to trip the breaker if a fault happens (we have subpanels in the center hallways of the house, so home runs are fairly short). The brittle insulation is another problem, but my father used top quality outlets and switches so we rarely have to mess with them.

Steve, Wa2wise ... thanks for the added info ... this report will take some time to fully digest.