Temporary Festival Wiring

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dema

Senior Member
Location
Indiana
I am a PE and have been asked to provide drawings for a stage performance. The customer says that the industry standard is to run SO type cable in Checkers Yellow Jacket. This separates the three phase cables by a little bit. There is a common lid, so I suppose it would be considered in a single raceway. He says the 4/0 cable is rated for 400A this way.

SO cable is in the 2008 NEC in table 400.5(B). I don't know where he's coming from. This is a three phase service. 4/0 appears to me to have a maximum rating under the circumstances of 316A.

I talked to him and some other people who have experience in stage productions - and they do truly seem to have experience - and they seem extremely confident that 4/0 cable is rated for 400A in this application.

I'm wondering if any of you can shed light on this.

While I'm at it - I will have two separate generators - one for light and one for sound, and will also have four light generators. The light generators don't need a ground rod. But both the other generators will. Both will serve the same stage. They are not paralleled.

I am wanting to connect the grounds on the two generators. If you have a separately derived transformer, you bond that to the building grounding system. Just not to any neutrals. Seems like it would be safest to have these two generator grounds bonded even though they are separate systems since they serve the exact same area. Any comments on that?

Thank you in advance for your help.
 
V

Volta

Senior Member
Location
Columbus, Ohio
dema said:
I am a PE and have been asked to provide drawings for a stage performance. The customer says that the industry standard is to run SO type cable in Checkers Yellow Jacket. This separates the three phase cables by a little bit. There is a common lid, so I suppose it would be considered in a single raceway. He says the 4/0 cable is rated for 400A this way.

SO cable is in the 2008 NEC in table 400.5(B). I don't know where he's coming from. This is a three phase service. 4/0 appears to me to have a maximum rating under the circumstances of 316A.

I talked to him and some other people who have experience in stage productions - and they do truly seem to have experience - and they seem extremely confident that 4/0 cable is rated for 400A in this application.

I'm wondering if any of you can shed light on this....
Click to expand...

He's kind of right, but it isn't SO. It is type W, or G. Table 400.5 will help. Single pole connectors, type 16 Camlock probably. 405 amps but the wires can't touch except at the wall of an enclosure.
 
V

Volta

Senior Member
Location
Columbus, Ohio
dema said:
...

While I'm at it - I will have two separate generators - one for light and one for sound, and will also have four light generators. The light generators don't need a ground rod. But both the other generators will. Both will serve the same stage. They are not paralleled.

I am wanting to connect the grounds on the two generators. If you have a separately derived transformer, you bond that to the building grounding system. Just not to any neutrals. Seems like it would be safest to have these two generator grounds bonded even though they are separate systems since they serve the exact same area. Any comments on that?

Thank you in advance for your help.
Click to expand...

Yes, I would absolutely bond them together at the sources.
 
kwired

kwired

Electron manager
Location
NE Nebraska
Looking at that table I would imagine just like 310.15(B)(16), if you have 75 degree terminations on your devices you have to use the 75 degree column. This likely means your 316 amps was for a 90 degree conductor, and now is 277 amps for a 75 degree conductor.
 
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zbang

Senior Member
Location
Roughly 5346 miles from Earls Court
Let' see-

IMHO per code, generator ground rods are optional (there's been much discussion about this), I do it anyway.
Bond all generator EGCs together. If you don't, it'll happen anyway at the stage through various unintended means.
Make sure that each generator has a properly sized SBJ. This means, of course, that the neutrals are all connected at the source.

Some people want a direct connection from EGC to stage structure, others allow equipment EGCs to provide that protection. I usually go with the latter.
Some people want a ground rod bonded to the stage structure, but I hardly ever see this. I don't see it doing much good, but isn't much work to install/remove.


The 4/0 cable should, as noted, be type W or SC. Per table 400.5(B), is rated for 405a at 90deg. I see lots of SC cable that has this into molded into the jacket. Do not use column F, that for multiconductor cable, column D is more correct. (Consider that even in YellowJacket, there is some ventilation that would not be possible in conduit.)
Terminal temperature is another matter, you'll have to look at that separately, but most temp. power gear takes this into account.
E1016 camlok connectors are rated for 105 deg.
(In the end, yes, it's common/accepted practice to use 4/0 at 400a. In most cases of actual use, it'll seldom see over 300, continuous anyway. Ask for a 400a feed, connect 250a load. That sort of thing.)

Article 520 isn't much help, but look to 525 and 590, then add a couple dashes of common sense.

PM me if you have other questions.
 
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