this will proably sound stupid but have had it happen. look for a fire ant bed near where the wire may run.they did this my fathers wood shop.they eat the insulation off of a 10/2 wgr uf cable. this was causing a 30 amp square D breaker to trip after a few minutes.found the ant hill ,dug it up & found about 3 inches of bare wire.as a matter of fact the ground was rather warm too.buried a new wire & have no problems since. weird huh?
