Derate Industrial Control Panel Condutors?

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jvondra

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Is it necessary to de-rate conductors inside of industrial control panels? If so, what Articles apply?

Thanks,

Joe
 
Re: Derate Industrial Control Panel Condutors?

Originally posted by jvondra:
Is it necessary to de-rate conductors inside of industrial control panels? If so, what Articles apply?

Thanks,

Joe
Click to expand...
No you do not have to derate the conductors in your panel.

310.15(B)(2) Adjustment Factors.
(a) More Than Three Current-Carrying Conductors in a Raceway or Cable......
Click to expand...
Your enclosure is not a raceway or cable. :)
 
Re: Derate Industrial Control Panel Condutors?

Unless inside the enclosure they are in a raceway such as wire duct.

BUT - in most cases, control panels have mostly non-current carrying conductors, so there is no heat so no derating is required for most of the conductors.

In some cases you may need to consider it though such as a panel that is mostly motor starters where there are current carrying conductors.

[ March 28, 2005, 06:57 PM: Message edited by: petersonra ]
 
Re: Derate Industrial Control Panel Condutors?

Originally posted by petersonra:
BUT - in most cases, control panels have mostly non-current carrying conductors, so there is no heat so no derating is required for most of the conductors.
Click to expand...
How do you figure that?
 
Re: Derate Industrial Control Panel Condutors?

Bob,
310.15(B)(2) ... or where single conductors or multiconductor cables are stacked or bundled longer than 600 mm (24 in.) without maintaining spacing and are not installed in raceways ...
Click to expand...
Don
 
Re: Derate Industrial Control Panel Condutors?

So you might have to derate if they are in a wire duct even though it isn't a raceway. But there is exception #1 (which I think petersonra was refering to):

"Where conductors of different systems, as provided in 300.3, are installed in a common raceway or cable, the derating factors shown....shall apply to the number of power and lighting conductors only."

Steve
 
Re: Derate Industrial Control Panel Condutors?

Originally posted by iwire:
Originally posted by petersonra:
BUT - in most cases, control panels have mostly non-current carrying conductors, so there is no heat so no derating is required for most of the conductors.
Click to expand...
How do you figure that?
Click to expand...
Most of the conductors carry little or no current inside a control panel. There is no heat generated in a #14 wire that has only 1/10 amp flowing through it.
 
Re: Derate Industrial Control Panel Condutors?

Originally posted by petersonra:
Originally posted by iwire:
Originally posted by petersonra:
BUT - in most cases, control panels have mostly non-current carrying conductors, so there is no heat so no derating is required for most of the conductors.
Click to expand...
How do you figure that?
Click to expand...
Most of the conductors carry little or no current inside a control panel. There is no heat generated in a #14 wire that has only 1/10 amp flowing through it.
Click to expand...
I was thinking that was where you where headed.

The amount of current carried by the circuit is irrelevant in the application of the NEC derating rules.

Now if you pointed out exception 1 as Steve did I would agree with you. :)
 
Re: Derate Industrial Control Panel Condutors?

If this is an Art 725 applicaiton then derating may not be required.

Art 430 part VI refers to Art 725. Make sure you understand what a class 1 ciruit is.
725.28 Number of Conductors in Cable Trays and Raceway, and Derating.
(A) Class 1 Circuit Conductors. Where only Class 1 circuit conductors are in a raceway, the number of conductors shall be determined in accordance with 300.17. The derating factors given in 310.15(B)(2)(a) shall apply only if such conductors carry continuous loads in excess of 10 percent of the ampacity of each conductor.

[ March 29, 2005, 07:37 PM: Message edited by: tom baker ]
 
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