310.15 (E)(3) Derating for neutral conductor

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philly

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I’m looking at an application that has a 480V 3ph -4w feeder to a panelboard which feeds several branch circuits as well as a sun-panel.

I’m looking at adjustment factors in 310.15(c)(1) to determine if I need to apply adjustment factors to consider 4 ccc’s in feeder raceway with neutral.

In looking at 310.15(E)(1) where this neural conductor is carrying only unbalanced 3 phase load then I would not need to consider neutral as a ccc.

However when I look at 310.15(E)(3) when there are a major portion non linear loads present I will need to consider neural at ccc. My question here is what is considered a “major portion” for non linear load makeup in regards to overall load? I have seen somewhere that when greater than 50 percent of loads are non linear than neutral would need to be considered ccc? To me this greater than 50 percent would also align with the term “majority portion”

Has anyone used or seen any guidance for this section when considering non-linear loads? There are several 1-pole branch circuits in panel that feed flourescent lighting and other non-linear loads. Would it be a good approach to take total connected non linear load in comparison to total connected load and if greater than 50% consider the neural a ccc?
 
philly said:
I’m looking at an application that has a 480V 3ph -4w feeder to a panelboard which feeds several branch circuits as well as a sun-panel.

I’m looking at adjustment factors in 310.15(c)(1) to determine if I need to apply adjustment factors to consider 4 ccc’s in feeder raceway with neutral.

In looking at 310.15(E)(1) where this neural conductor is carrying only unbalanced 3 phase load then I would not need to consider neutral as a ccc.

However when I look at 310.15(E)(3) when there are a major portion non linear loads present I will need to consider neural at ccc. My question here is what is considered a “major portion” for non linear load makeup in regards to overall load? I have seen somewhere that when greater than 50 percent of loads are non linear than neutral would need to be considered ccc? To me this greater than 50 percent would also align with the term “majority portion”

Has anyone used or seen any guidance for this section when considering non-linear loads? There are several 1-pole branch circuits in panel that feed flourescent lighting and other non-linear loads. Would it be a good approach to take total connected non linear load in comparison to total connected load and if greater than 50% consider the neural a ccc?
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I don't think I have ever counted the neutral as a CCC and probably never will. That section is super old and outdated and should probably just be deleted from the NEC. Pretty much everything electronic now is power factor corrected and not an issue.
 
Yes major portion is more than 50%. As EF stated this concept is pretty much obsolete and for the most part can be ignored.
 
infinity said:
Yes major portion is more than 50%. As EF stated this concept is pretty much obsolete and for the most part can be ignored.
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Thanks to you and EF for feedback.

I'm curious, is this because most electronic devices that previously created non-linear loads (lighting ballasts, battery chargers, etc...) have had technology improved to where the device has internal correction (PF etc..) to where it no longer presents significant non-linear load as seen by the system?
 
philly said:
I'm curious, is this because most electronic devices that previously created non-linear loads (lighting ballasts, battery chargers, etc...) have had technology improved to where the device has internal correction (PF etc..) to where it no longer presents significant non-linear load as seen by the system?
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That's pretty much the prevalent view. There isn't enough harmonic current to make it worth considering.
 
philly said:
Thanks to you and EF for feedback.

I'm curious, is this because most electronic devices that previously created non-linear loads (lighting ballasts, battery chargers, etc...) have had technology improved to where the device has internal correction (PF etc..) to where it no longer presents significant non-linear load as seen by the system?
Click to expand...
Remember the K-rated transformers for PC loads?
 
Appreciate the responses here. Are there any additional references or documentation that I search for the support the approach above? Looking for something that I could point towards to support approach aside from thread discussion. Thanks again
 
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