Re: L5-30 wire for 220V?
I have been the guy that found the bad wiring.
On regular Edison outlets in most constant use places (hotel ballrooms, salons, meeting rooms, convention/civic centers) are correctly wired and you can find someone who knows where the breakers are. However, I've found all sorts of interesting things, like neutral & ground wires twisted together and wrapped around the "un-hot" terminal of higher voltage services; ground/neutral swaps at 14-50 and 14-30 outlets... so I presume NOTHING.
Dealing with the aftermath of loose neutrals was enough for us to insist on real power taps, generators when practical, and having clients pay for modifications to existing services in necessary.
It ain't worth doing any other way.
Tim Mc
