Reply posted by Gene Pink on July 23, 2000

Same here, and my final and most inportant measurement is I look for 208 or 240 between the hot pins of two different outlets that are wired to different legs in my box. If it is there, I shut the breakers back off, and give the final OK to the fellows to connect up all the power cords, and power up. And sure as shit, there is an amp in a rack somewhere that didn't get shut off last time. That annoys the shit out of me, when you power down: gain control goes to zero, and switch the amp off, dammit. I hate unexpected power-up thwunks and ka-wumps when the amps should all be off.

I have pieces of red and black tape stuck on all the outlets in the distro to tell which leg they are on, and I carry this convention all the way into any racks that are wired for more than one leg. There are bits of red and black tape on each power amp, denoting which leg they get their power from. Even the twistlock cords have red or black sharpie marks next to their pins. So far it has been all but useless, but the time may well come when it will greatly aid in troubleshooting. ("all the power amps with black tape in a certain rack are out, must be a leg in the feed to it has opened up, check the black wire in the twistlock, all the way back to the distro")

Gene

Reply posted by greg on July 24, 2000

"Same here, and my final and most inportant measurement is I look for 208 or 240 between the hot pins of two different outlets that are wired to different legs in my box."

Anticipating the unasked questions among those still awake this deep into this thread :)

280V is what should be read between any two legs of a true 3-phase "wye" system. 240V is what should be read between the two legs of a standard 120V single-phase system.

Three-phase "wye" usually is printed on equipment as "120/208V Y". Single-phase shows up as "120/240V". Delta power (277/480 D) is useless in audio without a "wye" transformer: there is no neutral in delta (only three legs and a ground). Delta power is typically found in buildings where a lot of motor loads are found (factories, machine shops, etc.). Don't try to use delta power directly unless you have an ancestral or congenital hatred of your crew, yourself, your patrons or your gear.

There is also this bastard 120/120/240 three-phase configuration running around out there. Avoid it. Generators have a mode switch on them. You want 120/208Y for three-phase and 120/240 for single-phase. Insist on a ground rod. Don't give in, don't plug anything in, don't turn anything on without one. Don't connect the neutral and ground in your distro, especially in Pennsylvania.

Abide the instructions in this thread regarding generators, neutrals and grounds (if you can find the consensus, by all means let me know what it is). If you can avoid it don't use a three-phase source with a single-phase distro (it's not always possible to avoid doing so). The converse also applies.

The best thing to do before starting the generator is set the mode. Meter everything, including (and sometimes especially) utility service, before connecting. Go X-Y, X-Z, Y-Z (and should see 208 each time, within reasonable tolerances), then X-N, Y-N, Z-N, X-G, Y-G, Z-G, should see 120 (or reasonably close), then N-G (hopefully the reading is only a few mV at best). For single-phase, remove everything above that contains "Z" and substitute "240" for "208" and you're golden. Better yet, if you are unsure regarding any of the above, have a licensed (and bonded/insured) house electrician do your tie-in. (Have this in your contract).

Lives are at stake; don't let some itchy promoter talk you into cutting corners. Safety first. Safety first. Safety first. It's better to go on late than never go on again.

Wow, this got long-ish...

the 5¢ tour
greg

Reply posted by Gene Pink on July 25, 2000

Heh, heh. Kinda tough to sum up the subject of power in a 5 cent tour, eh? Especially without condensing things to the point where somebody's bound to disagree with something. But I'm tired tonight, maybe tomorrow.
;-)

This is why this subject is often revisited on here, there are enough finer points of it to fill a college course or three, and it is something we all should at least have a passing familiarity with, the stakes are too great not to.

Gene