Nomad... as long as the electrician is not black/white color blind, its pretty hard to wire a hot black lead to a white neutral or uninsulated copper buss bar....but again, mechanical devices can fail...It was easier with my older panel, that allowed you to pull a fuse block to isolate the grid... you make the assumption that if the main breaker isolates you from the grid, that it will isolate the grid from you... and then there is that word "assumption"... regards