Derating Wires

[delectric123]

How long can a PVC conduit with 9 - branch-circuit 4 AWG Cu conductors be before they have to be derated? Where is that found in the NEC 2011 Code Book?

 

[copper chopper]

310.15 pages 150 to 152, although I dont think the length of the conduit has anything to do with derating, only voltage drop.

 

[augie47]

310.15(B)(3)(a)

 

[delectric123]

i browsed that section and at article 310.15(B) (3) its says conductors without spacing longer than 24 in. Does that apply to single condutors in a raceway? Am i interpreting this right?

 

[augie47]

You are

 

[Smart $]

310.15(B)(3)(a)

No ampacity reduction for raceway lengths up to 24". 310.15(A)(2) Exception may provide relief to the lesser of 10' or 10% of circuit length.

 

[infinity]

Also Chapter 9 note (4).

 

[augie47]

True. I so rarely encounter that I forget it,

 

[delectric123]

Thank you, all, this is a very helpful forum. does the code have any derating requirements on bundled conductors in Industrial Control Panel Wiring? like conductors in a wire ductt? besides common sense

 

[Smart $]

Thank you, all, this is a very helpful forum. does the code have any derating requirements on bundled conductors in Industrial Control Panel Wiring? like conductors in a wire ductt? besides common sense

310.15(B)(3)(a) applies to ICP's that are not listed equipment (or a component thereof)...

where single conductors or multiconductor cables are installed without maintaining spacing for a continuous length longer than 600 mm (24 in.) and are not installed in raceways, ...

 

[Smart $]

310.15(B)(3)(a) applies to ICP's that are not listed equipment (or a component thereof)...

I should also add that it applies to field wiring in 'listed' ICP's.

 

[kwired]

There is this sentence embedded within 310.15(B)(3):

Where conductors of different systems, as provided in 300.3, are installed in a common raceway or cable, the adjustment factors shown in Table 310.15(B)(3)(a) shall apply only to the number of power and lighting conductors (Articles 210, 215, 220, and 230).

That to me means the control conductors are not counted as current carrying conductors when applying the deration factors of this section.

 

[delectric123]

would the 120VAC circuit powering the contactor coils be defined as control?

 

[Smart $]

There is this sentence embedded within 310.15(B)(3):



That to me means the control conductors are not counted as current carrying conductors when applying the deration factors of this section.

would the 120VAC circuit powering the contactor coils be defined as control?

Yes.