200+ CCC in trough after derating at 35%

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Mike Fleming

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I have a contractor who has installed a trough over 5 panels, there are over 200 current carrying conductors in said trough. They have pulled #10 wire but at 35%(Table 310.15(B)(2) I come up with that #10 being good for 14 amps, the contractor says the loads will never go over that and the OCPD is a 20 breaker. Am I correct in thinking that these circuits must go on a 15 amp breaker?
 
Mike Fleming said:
I have a contractor who has installed a trough over 5 panels, there are over 200 current carrying conductors in said trough. They have pulled #10 wire but at 35%(Table 310.15(B)(2) I come up with that #10 being good for 14 amps, the contractor says the loads will never go over that and the OCPD is a 20 breaker. Am I correct in thinking that these circuits must go on a 15 amp breaker?
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Doesn't really matter what the contractor says.
35% 0f 40 is 14.
15 amp breaker.
Unless someone else says different.
 
What is the load?

If all motors and minimum conductor ampacity necessary is 14 amps or less it is just fine, and could even have more than 20 amp branch circuit protection.

If serving receptacle outlets then your derated ampacity needs to be 20 amps or more if you have a 20 amp overcurrent device.

Most other things would be acceptable, but must have a 15 amp overcurrent device.
 
how would one get 200 CC in a single trough? that is a lot of CCC.

IMO if they really are all CCC, and the calculated load on the conductor is 14A, it is fine with a 15A CB.
 
Mike Fleming said:
I have a contractor who has installed a trough over 5 panels, there are over 200 current carrying conductors in said trough. They have pulled #10 wire but at 35%(Table 310.15(B)(2) I come up with that #10 being good for 14 amps, the contractor says the loads will never go over that and the OCPD is a 20 breaker. Am I correct in thinking that these circuits must go on a 15 amp breaker?
Click to expand...

While agree with Kwired, one other thing to consider is that the derating only applies at any given cross section, so depending on how the conductors are installed may have an effect on the derating requirements.
I realize that the 2011 NEC does not specifically say this, but that has always been the intent. The 2014 NEC has made this clear.
 
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