ECN Forum Forums General Topics of the Trade General Discussion Area Temporary Power Hookups....

iwire wrote:


The 1999 edition of the NEC does not include the "indoor or outdoor" reference. I would presume earlier editions also do not. So that could be where the mindset originates. I'm not saying it's right, but if it's not pointed out, well....

In reference to my comment that building of distros was common practice:


THe '99 NEC seems to allow this, based on ART. 520-62:


I would think that most distros would be readily in compliance with those provisions, merely because any touring company worth more than a nickle knows that safe, reliable power is crucial. Most performers won't work again with any company that has equipment breakdowns during a show.



Art. 520-53(4)(j) specifies the number of interconnects allowed and the maximum distance from supply to switchboard of 100 feet. (No more than 3 interconnects up to 100ft, then allows one additional interconnect for each additional 100ft.) Again, I'm looking at 199 NEC. Did 2005 change this? And this article seems to apply only to "Portable Switchboards On Stage". The above Art. 520-62 appears under the subsection (E) "Portabe Stage Equipment Other Than Switchboards". I submit the postion that the limitation on distro feeder lenghts and allowable number of disconnects does not fall under the limits in Art. 520-53(4)(j)......

Also, I would think that coiling up an excess length of feeder would be a very bad idea due to heating and inductance.

As someone here once asked in another thread "The NFPA is a tombstone agency. How many deaths can be attributed to...." So how many injuries/deaths are attributed to multiple connectors in a distro feeder? In other words, has historical usage proven it to be an inherently unsafe practice?


Now I'm confused here. What difference (electrically) would the connection means make? (Let's not debate the bond to structure created by a metallic conduit, for example). I would think a ground rod is a good idea, regardless. This was demonstrated by a real incident.

A big name performer came into our venue located by a lake. (He currently shills for a casino in So. Cal.) His lighting rig was stadium-size, with a lot of the Vari-lites (those moving, color changing spotlights you see all the time.)

They brought in thier own genny to power the lighting rig. (House power was only 200 amp, 3phase.) The rack with the control computer was connected to house power via a grounded outlet.

Shortly after firing up the genny, we could smell the lovely odor of burning electronics, but could not locate where it was coming from. It seemed strongest in the middle of the house (?) which was well away from any gear. (??) After some searching, I pinpointed the smell to the Power conditioner in the computer rack. I told their tech, and we shut down and opened the power conditioner up. The N-GND MOV's were totally fried!! We were both puzzled. I then suggested we plug the rack in with a ground lift so I could meter the voltage from the rack to ground. What did we find? 180+ volts!! Connecting directly to the wall (no lift) and using the other half of the duplex we still got around 90 volts G-N. WTF?? Unplug the rack and G-N dropped to about 1 volt! Double WTF??

I suggested that the genny and "shore power" ground obviously was not bonded together, creating the difference. And that maybe they should power the computer rack from the genny to stop the problem.

The know-it-all tech said no way, it'll work for the show just like it is, no big deal.

Well during the show, they lost five! of the vari-lite interface boxes, two down in flames, two with a lot of smoke and one which knocked the roadie on his butt when he went to change it. (This in addition to the three boxes lost during the day.)

What caused all this carnage? I went outside to look closely at the genny, followed the ground lead to find IT WAS JUST THROWN INTO THE LAKE!!

Did I mention the hookup was done by the same know-it-all?

I talked to the resort's sparky and asked him if we could drive a "permanent" ground rod to prevent this happening again. (The gennys all ended up in the same location, so I thought it was a good idea. Or at the least, that the genny be grounded to the ground lug in the lighting disconnect (although looking back now, I don't think that would be legal.)

As I'm sure iwire and techie can attest, there are so many variables involved in setting up at different venues, each one is unique and sometimes even a familiar venue changes in ways that throw a wrench into the best-laid plans.

The most important thing is to work safe, ensure reliable power for your client and maintain high safety standards to protect workers, performers and the public.

Whew, that was a marathon post....

edited to fix html
third time's the charm
[This message has been edited by mxslick (edited 08-09-2005).]

[This message has been edited by mxslick (edited 08-09-2005).]

[This message has been edited by mxslick (edited 08-09-2005).]