Call on a small W/I freezer- An old Hussman condensing unit on the roof. The unit breaker was tripped- reset and BAMMM! Flash and trip.
Took a while to find it, but a feed to the LL solenoid valve from the control panel was connected by a close nipple with plastic bushings on both ends.
There was slack in the wire (#16 THHN) to the coil,but it still wore through the bushing till the hot leg hit the nipple. BOOM!
Took about 20 years, but...
A little pookie stuffed in the hole... might have save the problem.