Went on a service call to investigate the cause of a small fire and make repairs since the fire company was unable to do so. The fire had occured outside at the rear of the house. I noticed the burned wood near the eave and also notated the roof flashing had burned and split apart in the same location.
There weren't any wires near the origination point so I scratched my head for a little while, then on a hunch I tested the burned flashing with my volt meter. Sure enough it read 120volts. I traced the flashing around the perimeter of the house to the other side where a flood light was attached, then located the corresponding breaker and opened it. Rechecked the voltage on the flashing and this time it was zero. I'm sure you probably know where this is going now.
Anyway, to make a long story short, whoever installed the flood light didn't connect the ground, and when he screwed it in the stem had pierced the hot and energized the whole thing, including the flashing behing it. And since the ground wasn't hooked up, it never tripped the breaker. It just stayed energized for who knows how long until it finally found a way to arc itself out.
There weren't any wires near the origination point so I scratched my head for a little while, then on a hunch I tested the burned flashing with my volt meter. Sure enough it read 120volts. I traced the flashing around the perimeter of the house to the other side where a flood light was attached, then located the corresponding breaker and opened it. Rechecked the voltage on the flashing and this time it was zero. I'm sure you probably know where this is going now.
Anyway, to make a long story short, whoever installed the flood light didn't connect the ground, and when he screwed it in the stem had pierced the hot and energized the whole thing, including the flashing behing it. And since the ground wasn't hooked up, it never tripped the breaker. It just stayed energized for who knows how long until it finally found a way to arc itself out.