Just about every "alphabet" group you can think of recently took part in a survey of older homes, and their electrical systems.

30 homes, slated for demolition, were examined from service drop to outlet. Components were sent to a lab for further examination and testing.

With the NFPA asserting over 24,000 household fires - and a disproportionate share of these being in homes older than 40 years - are caused by the electrical system, what causes do you think the study found?

(I'm cheating ... I have a preliminary draft of the report ... I just want to see what "conventional wisdom" thinks )

I suspect homeowner modifications will rank high on this list. As will deteriorating insulation. And probably a certain amount of damage from rodents, birds, and the like.

I expect there will also be assorted problems at receptacles.

Thirty homes is a small sample considering the number of homes that don't burn down. I would guess that very few had electrical problems.

I think most problems are on the load side of the outlets.

I have to agree with Greg that what is plugged-in would be a primary cause. A lot used to be attributed to 'overfusing', in the days (and areas) that edison base fuses were prevelant, of which I saw my share.

I remember the guy at a local hardware store commenting something to the effect of....'we used to sell a lot of 15 & 20 amp fuses; but since a lot of people started buying the 30's, sales have slowed way down'.

Fire cause determined to be caused by 'electrical' seems to be vague; it should be broken out into utilization equipment and premises wiring.

I'd say improper use of extension cords would be #1 and fuse tampering would be #2. I get so mad when they report a fire on TV news and cite the cause as being electrical. Later they report that three portable heaters were plugged into a 100' 16/3 extension cord. That isn't an electrical fire.....That is a stupidity fire.

Something tells me that aluminum wiring is going to get thrown under the bus on this report too.

Actually ... aluminum missed the bus - this time! The houses all pre-dated the aluminum wiring craze.

I'm right there with you on this!!!
But I say "Fire alarm" and my insurance rates (liability) go right thru the roof !!!! I prevent this crap!!! (Or at least detect it)
But I digress.. I will go with poor/loose connections at the devices. Wich coincides with the overloading of appliances. (whoa.. Both ends to the middle. Smooth.. No?):)

As stated above, I'm sure deterioration from misuse on the load side is gonna be right up there.

Also, I would guess that, if the homes were old enough, they probably found quite a few exposed wire joints. I've found that the old solder-and-wrap method of wire joining, although good from an electrical conduction standpoint, suffer from deterioration of the wrapping materials and don't handle maintenance and handling too well. Also, a few times being pulled in and out of the junction box for add-ons and repairs tends to break up the old cloth insulation pretty badly too.

So, I would guess that they would classify this as "post-build maintenance damage", or something like that.

Induced voltage is also prevalent in these old installations.

Improperly bonded and altogether loss of the grounding system also comes to mind.

BTW, what a great idea for a study... I'm sure there was quite a bit to learn from this. I would have loved to have been on that archeological dig.