Question for those who work on these situations professionally... I run sound and lights for band and commonly work in clubs where the only quality power available is an older style 30A to 50A "range" or "dryer" style outlet with 2 hots and a neutral. I have used some "distros" built by others where they split each hot through a 20A breaker to an Edison quad box. The grounds are then simply "tied off" inside the distro box, without any real ground connection. Interestingly, the typical outlet tester shows this combo as valid but I wonder about the safety! Would it be better to bond the Edison outlet grounds to the Neutral line, as I think was done with appliances until the code changed to the newer 4-prong outlets? Or, should I make my own ground connection to available cold water pipe, etc.. ?? None of this optimal, but looking for the safest most logical thing to do for temporary hookups... thanks!
Wow, you have a "real world" stumper there, considering the temporary nature of the hookup. I think you are on track about finding a way to ground things out, but the problem seems to be that you can't rely on some cold water pipe and its bond to the panel for a ground...unless you have traced it all out and you definitely can see that such bonding is complete and things are connected tightly (though it wouldn't be code to be doing this, in your world, it seems to be the practical choice to make). As far as the outlet being ungrounded, except through a neutral, that scenario only held for residential work, not commercial, so there should be a separate equipment ground at that 220 outlet. My guess is that the outlets were an add on outlet, and probably wasn't inspected, so who knows how it might be miswired? What's a "distro"? Just a box for multiple 120V plug-ins?
#22586 - 02/26/0310:32 PMRe: Grounding a 3 prong Range/Dryer Outlet?
Yeah, "distro" is just sound and light guy/gal slang for any sort of "power distribution box", usually consisting of a Square D load center mounted on a sheet of plywood with a handful of 20A breakers feeding various 110v Edison quads and some sort of Hot-Neutral-Hot-Ground 220v incoming. Can also be more formal with an "entertainment quality" 60A Hot-Hot-Hot-Neutral-Ground connector coming in through "camlocks" (quick disconnects). Companies like Motion Labs make pro level distros but naturally with a price tag attached! Thanks for the info.
#22587 - 02/26/0311:17 PMRe: Grounding a 3 prong Range/Dryer Outlet?
AeroSKI5150 Are you with Aerosmith?
#22588 - 02/27/0307:40 PMRe: Grounding a 3 prong Range/Dryer Outlet?
Don't I wish... in that case I'm sure there would be no budgetary constraints on getting quality power, not to mention not fooling around with hole-in-the-wall clubs using dryer and range outlets for stage power!