A Corroded Ground, & some of those "They'll last till they melt, or something burns" lunatic fuses.
I've seen Home, & Business Owners do this, but with Copper Piping cut down to the right length, in their Service Disconnects for Equipment, & even in very old Main Service Boxes, where they got tired of replacing the Cartridge Fuses.
The majority of time that led to Compressors burning out, & in a couple of cases, even a fire.
And Ya'll shoulda heard the Home/Business Owner b**** about the cost of repairing the damage, or replacing everything that melted down.