Mains Power for Live Sound/Lights

Hey all, does anyone have any experience with  pulling power directly from mains for live sound and lighting? When I was touring, I used to see sound/lighting providers "clamp" on to the main feeds of electrical panels, and go from there to their own breakers and distros. I've grown to the point of having sound/lights tripping breakers at some events (where power was not designed for such). Plenty of information on the web about the distros with the camlocks and all once you have the feed, but I can't find anything about "clamping on" to get the feed in the first place.
Thanks,
-Glenn

gltech said:

... I used to see sound/lighting providers "clamp" on to the main feeds of electrical panels, ...

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Please don't ever do that. Dangerous. That sort of thing is probably what inspired the NEC to write a code book.

Decades ago, there was a product called a Tweako meant for this, but they fell out of fashion due to the rampant spread of common sense. I have even seen automotive jumper cables cut in half and spliced to feeder cable to get four clamps, used for this. Two hots, neutral and ground, any of which can fall off at any time.

The usual way these days with 120/240 is to build a proper 240 single phase breaker panel, add a good length of 6/4 SO cord (with 50 amp twistlock extensions, same plug as most trailered rental generators), and carry a tool box with a good assortment of various brand dual 50A breakers. Remove panel cover, wire up proper, and plug mating breaker into unused spaces.

For much, much more info, go here:

http://forums.prosoundweb.com/index.php#c1

and browse the "AC power and grounding" sub board.

Gene

Nobody in the professional world does any kind of "clamp on" or live tie-in these days. The bigger venues will have a "company switch" with dedicated fuses/breakers and usually camlock outputs.  Some older places may still need bare wire tails to tie in, but that should be in a dedicated box that can be completely shut off before opening the door to make the connections. 

Or for smaller venues some kind of multipin high current plug is often found.  Probably more common in Europe than the USA.

+1 to Gene's advice to check out Prosound Web  http://forums.prosoundweb.com/index.php

Lots of professional sound people, and the occasional beginners. 

AC Power and Grounding http://forums.prosoundweb.com/index.php/board,82.0.html is the target subforum for power questions.

For general sound reinforcement questions perhaps start in Lab Lounge http://forums.prosoundweb.com/index.php/board,10.0.html before annoying the more professional  LAB Classic Live Audio Board, with simple questions.

BTW real names are required over there and they do not suffer nonesense.

JR

I did that once in my life when I had to do a stadium open air in Kigali/Ruanda. The stadium was built by chinese and everything inside the mains distribution was written in chinese. No chance to find out what breakers they were using. Luckily they have a 230/400V 3phase system like we have in Germany.
I had to clamp on in front of the main breakers. Actually it was not clamped but screwed to the screw that held the incoming side of the chinese main fuse. These fuses looked to me like a small version of a german NH fuse. Too small to handle my system.
Everything from this point was a DIY solution I put together in a long, long day. I basically drove through Kigali with a guide, stopped at every electric-store and bought whatever german material they had. Out of these parts I made a distribution for my 40kW PA and >100kW light system. The show was happening, but my PCM70 never worked which meant I had less than 195V at FoH. With every kick drum beat the console´s lights went down.
The largest wires I could get were 6sqmm. From mains inlet to the stage we had app 130m and all I could get was 200m of 6sqmm. So I did two lines with 100m of 6sqmm and then distributed to four lines with 4sqmm up to the stage. Those distribution panels were screwed on a wooden plates, lying in the middle of the crowd. No kidding. The promoter organized police guys to stand next to those panel, making sure that nobody would mess with them. The rest to the stage has been done with 4sqmm. The largest connector system I could find was 32A CEE connectors, so we used that for everything. Luckily no german authorities had to check that mess  ;D They´d have imprisoned me instantly.
The local tech guy (who was an EE) was quite impressed by my solution. He said that this was more professional than anything he had seen in Ruanda before. I´ m not sure if that was a honour  :-\ Luckily he was able to provide all the measurement tools to proove el. safety and grounding.

I've seen it done. I feel lucky I wasn't blinded by the flash.

Thanks for all the info guys. Pro Sound Web looks good.

Gene Pink said:

The usual way these days with 120/240 is to build a proper 240 single phase breaker panel, add a good length of 6/4 SO cord (with 50 amp twistlock extensions, same plug as most trailered rental generators), and carry a tool box with a good assortment of various brand dual 50A breakers. Remove panel cover, wire up proper, and plug mating breaker into unused spaces.

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Thanks Gene - that was my original thought, but I wondered "what if the box is full?" And I need 150 amps or so on each side of the stage.

gltech said:

Thanks for all the info guys. Pro Sound Web looks good.

Thanks Gene - that was my original thought, but I wondered "what if the box is full?" And I need 150 amps or so on each side of the stage.

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This is not my area of expertise but I believe there are commercial distros available with different feature sets, and only qualified electricians are supposed to tie in the tails to facility power.

JR

Scodiddly said:

Nobody in the professional world does any kind of "clamp on" or live tie-in these days. The bigger venues will have a "company switch" with dedicated fuses/breakers and usually camlock outputs.  Some older places may still need bare wire tails to tie in, but that should be in a dedicated box that can be completely shut off before opening the door to make the connections. 

Or for smaller venues some kind of multipin high current plug is often found.  Probably more common in Europe than the USA.

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I wish we had German inspectors checking electrical wiring in Balkan which is also part of Europe. Clamp on and live tie-in are still practice at some venues, lately not as often as they used to be. Btw, once we had to put two line arays on stage boxes by hand instead of "elevator", beneath was wooden floor. Of course we told them wheels and floor will crack and of course they did. They forced us do it because guy with the key to do it properly would cost 100eur. Very, very dangerous situation for about 8 guys, that was the last time i worked live. At least bigger shows, i still do smaller sometimes, if things are normal.