Derating Advice.

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markebenson

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I have a dedicated 200a 3ph panel for lighting, audio amplifiers, and general edisons for bands on a stage. All indoor.

1. The edisons will have 6 20a circuits rotating evenly between 14 quads spaced out about 7 ft on center first one 10 ft from the panel.

2. There will be 6 20a circuits run to a J box for lighting about 30 ft from the panel. This will be mostly LED fixtures.

3. There will be 12 20a circuits run to a J box for Audio Amplifiers about 30 ft from the panel.

Advice on derating and # of conduits please?

Thanks :)
 
You need to determine the number of CCC's in each section raceway. If you have separate neutrals for each circuit then all of the conductors would be CCC's.

For 20 amp circuits if you have:

9 or less CCC's you can use #12 THHN conductors
10-20 CCC's you would need #10 THHN
21-30 CCC's you still might be able to use #10 THHN depending on what's at the end of the run. If you have multiple receptacles on those circuits you will need #8 THHN

Once you determine the conductor sizes you can go to Annex C in the back of the NEC and determine what size raceway you will need based on 40% fill. Raceway sections 24" or less can use 60% fill and do not require derating.
 
But, remember that the conduits on the stage create trip hazards... which is why it is normal to have a sub stage that you carry in to place over the current stage, so you have plenty of cover. Of course, the use of more conduits to parallel your circuits is common as well. Plus, remember to keep your runs separate for your audio gear... one reason why wireless mikes are becoming a rage even in churches... though they are a headache for any sound man.
 
Thank you very much.

I have one more question?

2/0 Copper THHN run in emt to a 3 phase sub panel 100ft away. What would be the proper fuse rating?
 
jumper said:
You edited! Gimme a sec. Are the majority of the loads non linear?
Click to expand...

The answer to that question leads to 310.15(B)(5)((c),

which means you then go to Table 310.15(B)(3)(a) Adjustment Factors for More Than Three Current-Carrying Conductors

Consider the load per 220, check T310.15(B)(16) and then see if you can apply 240.4(B) if needed.

So, possibly 175A or 140A. Breaker/fuse 175; 125 or 150 depending.
 
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