The electrical industry does a lot of experimenting on the result of short circuiting; especially in high voltage and high amperage conditions.  The man on the job often experiences … er … experiments with these situations by accident.

One time I was working on a large electrical panel located in the office of a business.  The business owner told me that I could not turn the power off as he was in the middle of making payroll using a computer.

In the course of my work I discovered a loose connection in the deep interior of the panel.  Very carefully wending my way through the maze of wiring and connections, I was trying, with great diligence and care, to tighten the connection with a screw driver.

Of course this would be the time that the screw driver would slip.  It did.  There was an explosion.  For a few seconds I couldn’t see.  Slowly my eyesight returned and I recovered from the electrical flash.

Fortunately, I was wearing glasses.  There were bits of copper that had splattered on, and welded themselves to, my eye-glass lenses.  The arc ruined about 3 breakers and disintegrated a number of buss jumpers.

The owner came running out of his office saying (loudly); “I told you I couldn’t have the power shut off!”  What could I say?  It took me a couple of hours running around town to find the parts I needed and to install them to get the power back on before the day ended.

For some strange reason I was never sent back to that job.

The above account reminds me of another instance where an electrical disconnect, rated for inside (weather protected) installation, had been used in an outside installation.  There were two guys working on the job.  One was standing behind the installation and the other at the front of it.  This particular installation had electrical gear on both sides of a board.  The whole unit was standing out in the middle of nowhere particular, unprotected from the weather.  The guy at the front tried to turn off the power by activating the improperly installed “inside” disconnect.  The electrical disconnect would not operate because water on copper had effectively “welded” it in place so that it was stuck.

The guy in the front jerked real hard on the handle and the whole thing blew up in his face.

At the hospital he was told the one thing that saved his face from being fried was his heavy beard.

Such instances are what have prompted many OSHA safety rules and NEC requirements for properly using equipment rated for the environment in which it is installed.