I must confess to knowing only a little about American house-wiring, as a Brit living in rural France, but I do watch "This Old House" and "NYW" on satellite. A fault does not have to be in the fixed house-wiring. Practically very appliance is sold with a 'flex' made up of multiple conductors, which are vulnerable. Any idiot can (and I did!) drape the flex anywhere he or she likes. In my case, I parked the washing machine nipping the cable, where the machine vibration could mangle it for several months and break some of the conductor wires. There's no overload, the appliance is using normal amps, the house wiring is ok, no electrician is at fault. I won't say 'to Code', because here in France there are few if any Codes- as my Maire says- "You 'ave builded a 'ouse. It felled over. What has that got to do with ME!?"
The flex got hot- it's copper area was too small, and the insulation degraded- quote "turned to dust".
I think the polymers they put in the PVC to make it flexible evaporate with heat. The wires are now exposed to oxidation, and further damage occurs. In our case my wife smelled burning plastic and pulled out the plug, but not before the flex had scorched a neat black slot in the plastic trim and charred the unit side. But what might have happened if the fault were parked over a newspaper on the floor (ie Dog's-Dinner-Place) and the local temperature had risen to 451F? The breaker will not operate unless excessive amps flow. I thought such a thing would be impossible- Why didn't the live(hot)/neutral/earth(ground) short? Why didn't all that carbon conduct and short?
Ah, the mysteries of Elec-trickery!
