200% Neutral and Derating

[infinity]

I have a feeder where the engineer specified a 200% neutral in both the panel bus and in the feeder. Not knowing the load, would you automatically assume that based on this design that the neutral is considered a CCC?

 

[kwired]

If 200% neutral is specified, I guess I am expecting there to be significant non linear line to neutral load, so yes in most cases.

 

[Smart $]

Agree... but I tend to believe many engineers are superstitious when it comes to triplen harmonics effects.

 

[GoldDigger]

Odd question: Where the EGC size or bonding jumper size is based on the circuit conductor size, would the 200% neutral also end up forcing a larger minimum EGC?

 

[ron]

If the neutral is oversized, then an upstream transformer will likely need to be K-rated if within the owners control.

 

[ActionDave]

Odd question: Where the EGC size or bonding jumper size is based on the circuit conductor size, would the 200% neutral also end up forcing a larger minimum EGC?

No it won't. 250.66 is based on the size of the ungrounded conductor and 250.122 is based on the size of overcurrent device.

 

[infinity]

Agree... but I tend to believe many engineers are superstitious when it comes to triplen harmonics effects.

I agree in most cases it's just over design and a waste on someone's money.

 

[kwired]

No it won't. 250.66 is based on the size of the ungrounded conductor and 250.122 is based on the size of overcurrent device.

250.122 is based on overcurrent device, but also requires increase in size if ungrounded conductor is increased in size - no mention of grounded conductors though.

 

[infinity]

250.122 is based on overcurrent device, but also requires increase in size if ungrounded conductor is increased in size - no mention of grounded conductors though.

Yup, an increase in only the neutral size doesn't change the required EGC size.