"toller" wrote in message ...
Circuit breakers do go bad and fail to trip on overloads, but it is unusual.
More commonly they trip unnecessarily when they fail.

But, they will not trip on arcs unless there is also an overload. Arc fault
circuit breakers were invented for precisely that reason; to protect against
arcs that did not involve overloads.
They outlet was probably damaged, and that is what caused the problem. The
breaker is "probably" okay, but unless you want to test it, you might rest
easier replacing the breaker. Hey, why not replace it with an arc fault
breaker?!

Could the arc have been caused by bad wire? The outlet was only one
year old, but the wiring is very old. Someone suggested that the wire
is too old and needs to be replaced. If it is charred, can it just be
cut back and used again?