Ugh!!Installed a heating and cooling system in an attic a few years ago.Got a call that winter that the unit was leaking water into the bedrooms. Hmmmmm. Went to check and the home owner installed a whole house humidifier....he ran a 1/4" water line into his attic. Attic is not heated and on a 0 degree day the line burst. Talk about a mess!!!That was NOT a good idea!!
On the electrical side I always have a tester in my tool belt.I can't count the number of Cable cutters and Side cuts that have been melted into uselessness. I also test all new or temp power sources.You should see what 240 volts does to a 120 volt floor sander!
My 120vac shop vac sounded like an F18 on take-off when plugged into 220v but it really had great suction fot 10 seconds or so