Determining what is a current carrying conductor

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JJKMM

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Signal & motor control conductors are not considered current carrying conductors, what if you had a very large starter/contactor which the holding current may be 4amps would these be considered CCC? What about conductors feeding solenoid valves ( 0.5a to 3a draw) and other low current control device?
 
We really need to know if the conductors in question are "power or lighting conductors" because if they are not, then the do not count for the purpsoe of derating per exception #1 to 310.15(B)(2). In my opinion, these conductors are not power or lighting conductors, but those terms are not defined in the NEC.
Don
 
For the sake of common sense. If they carry current they are CCC. Now, wiring in control panels may not fall under NEC jurisdiction, but they do go somewhere. Treat them as CCC and you will not have any issues to concern yourself with.
 
don_resqcapt19 said:
John,

So for the purpose of derating you count all grounded conductors as current carrying conductors?
Don
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That's what they keep telling me. lol
 
wanderer20001us said:
I believe you do count them unless they are part of a multi-wire branch with a shared grounded conductor.
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Even then they may count, if there is a high percentage of harmonics present.
 
JJKMM said:
Signal & motor control conductors are not considered current carrying conductors, what if you had a very large starter/contactor which the holding current may be 4amps would these be considered CCC? What about conductors feeding solenoid valves ( 0.5a to 3a draw) and other low current control device?
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I believe they are not current carrying per the NEC definition.

Keep in mind the reason for defining a CCC is to prevent conductor insulation overheating. A conductor drawing 4A produces only about 15% of the heat as the same conductor at 15A.

There is nothing preventing you from considering it as CC if you so desire and derating accordingly.
 
What do you consider a '...major portion...' when considering the harmonic content, 1/3, 1/2, 1/4? Do you also consider that actual harmonics (3rd, 5th, 7th...)? Has anyone been called on this by an inspector in the field? I'm just curious because 310.15(B)(4c) seems a little vague.
 
wanderer20001us said:
What do you consider a '...major portion...' when considering the harmonic content, 1/3, 1/2, 1/4?
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I don't know, and I haven't yet encountered a design in which it came into the discussions. I don't even know for certain what parameter is being measured, in order to compare percentages. For example, "half the loads have harmonic content" is different from "half the energy being transmitted is transmitted at a harmonic frequency."
 
In a typical office setting, I would consider the desktop computer, CF lighting, and most of the rest of the electronic gaggets in the average cubicle non-linear in nature. Yet, the home runs out to the cubes from the panel almost always take advantage of the shared grounded conductor not counting as a CCC to minimize the conduit runs. Add then there is future use when the loads on existing brances changes. Short of a data center installation, I think it would be hard for the AHJ to know what is appropriate for the installation loads.
 
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