To make a long story short, the 1960s vintage lightwall conduit running through our house's concrete slab wasn't going to last forever. I suspect that at some point it took on a little water, and this summer it finally corroded enough to pinch the insulation on one of the wires. (Incidentally, he could not pull any of the other three wires out because they were so tightly wedged in the conduit.) I should have been more suspicious when the three-way switch function for the overhead lights on that circuit quit working.
For a few months, we worked around that by just leaving one switch on. But when the circuit breaker popped this time, it also shut off the furnace. I hadn't realized it was on the same circuit when it popped one or twice in the summer. But we woke up kind of cold on Saturday morning, which brought it to our attentions, so we put in a call to the electrician.
Suffice it to say I'm sold on the value of circuit breakers (and good electricians).
