Theater Lighting

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arnettda

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I am bidding a change out of a schools theater lighting system. The dimming panel now is located on a mezzane level with the patch panel down on the stage. They are replaceing the dimmer panel and turning the patch panel into a big J box.They ran a 750 MCM AL from the dimer pannel down to the patch panel for the neutral and then 12's for the ungrounded conductors. There will be more dimming ckts now than before so lots of new ckts being brought up to the dimmer panel. If I leave the 750 for the neutral and run new branch ckt ungronded conductors only will I run into trouble having all hots in a pipe? I will need more than one pipe. The main feed comes into the dimming panel on the mezzane. I have read 376.22 & 520.6. Any past experience or other places I should look in the code would be appreciated. I am calling my local inspector in the A.M. but would like others input. Thanks Dave
 
arnettda said:
I am bidding a change out of a schools theater lighting system. The dimming panel now is located on a mezzane level with the patch panel down on the stage. They are replaceing the dimmer panel and turning the patch panel into a big J box.They ran a 750 MCM AL from the dimer pannel down to the patch panel for the neutral and then 12's for the ungrounded conductors. There will be more dimming ckts now than before so lots of new ckts being brought up to the dimmer panel. If I leave the 750 for the neutral and run new branch ckt ungronded conductors only will I run into trouble having all hots in a pipe? I will need more than one pipe. The main feed comes into the dimming panel on the mezzane. I have read 376.22 & 520.6. Any past experience or other places I should look in the code would be appreciated. I am calling my local inspector in the A.M. but would like others input. Thanks Dave
Click to expand...

Code issues aside, most modern theatrical dimming systems require a dedicated neutral/circuit to the dimming rack. I am not sure which manufacturers are spec'd out, but I would be surprised if ETC, Strand, or Leviton would actually energize a system installed as you describe. Also be warned, most of them are not UL listed for AL feeders.
 
....most modern theatrical dimming systems require a dedicated neutral/circuit to the dimming rack.
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That should read as the LOADS of a modern dimmer require dedicated (separate) neutrals to each dimmer (or channel.)

DO NOT try to install or energize the system as it is. Pull that 750 neutral out of the pipe and pull in the required number of neutrals. And to be Code compliant, sounds like you need to re-pull some of the hots to get each dimmer's hot and neutral in the same pipes.

Attempting to share neutrals on the load side of modern electronic dimmers WILL result in failure of the dimmer modules, which will NOT be covered by the manufacturer's warranty!!

Calculate the wire and labor accordingly. If the client argues that "it worked before" don't back down. It wasn't Code compliant before. :)
 
I don't like "MeToo" posts, but well, you really need dedicated neutrals from the load recepticals all the way back to the dimmers. Since you're just bidding it right now, spend some time on the phone with the dimmer manufacturer talking about their requirements. Most of them should have something online, too.
 
mxslick said:
Attempting to share neutrals on the load side of modern electronic dimmers WILL result in failure of the dimmer modules, which will NOT be covered by the manufacturer's warranty!!
Click to expand...

Kill the warranty I have no doubt, causing failures I would need to see a legitimate explanation for.
 
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