# NEC problem



## EEpowerOK (Oct 21, 2013)

In a field-fabricated installation with a nominal voltage rating of 34.5 kV, the minimum air separation between bare live phase to phase conductors outdoors is what?


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## iahim (Oct 21, 2013)

15"? Table 490.24


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## EEpowerOK (Oct 21, 2013)

correct, that was a tricky one, I'm always looking in ch1,


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## iahim (Oct 21, 2013)

Same here. I looked in 110 first


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## saberger_vt (Nov 13, 2013)

I agree on article 110, except that article 110 is for "equipment" not conductors. My first thought was to look in article 310. But again, that is for wire amperage even though their are some nice charts on high voltage ducts and so forth. Knowing that it's in Article 490, I checked the index on this one "Conductors, over 600v", and it specifies Article 490.

NEC questions can be very obscure, the questions are not meant to be "tricky", you just need to be able to read all the information and decide what parts of the question are relevant to finding the solution. I'm sure I missed a few questions on the exam just based on that alone!!!


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## Zack J. (Nov 21, 2013)

How do you know it's 15" and not 18"? Based on the table 490.24 it would seem that you would need to know the BIL of the device in order to answer the question.


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## iahim (Nov 21, 2013)

Zack J. said:


> How do you know it's 15" and not 18"? Based on the table 490.24 it would seem that you would need to know the BIL of the device in order to answer the question.


Because the problem asks for minimum distance.


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## Insaf (Dec 15, 2013)

iahim said:


> Zack J. said:
> 
> 
> > How do you know it's 15" and not 18"? Based on the table 490.24 it would seem that you would need to know the BIL of the device in order to answer the question.
> ...


Both 15" and 18" are minimum distances for BIL 150 (kV)and 200 (kV) respectively.


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## Insaf (Dec 15, 2013)

iahim said:


> Same here. I looked in 110 first


I don't see any clearance distance 15" in 110. Would you please specify the sub-number of article (e.g. 110.xx)?


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## Insaf (Dec 15, 2013)

saberger_vt said:


> I agree on article 110, except that article 110 is for "equipment" not conductors. My first thought was to look in article 310. But again, that is for wire amperage even though their are some nice charts on high voltage ducts and so forth. Knowing that it's in Article 490, I checked the index on this one "Conductors, over 600v", and it specifies Article 490.
> 
> NEC questions can be very obscure, the questions are not meant to be "tricky", you just need to be able to read all the information and decide what parts of the question are relevant to finding the solution. I'm sure I missed a few questions on the exam just based on that alone!!!


 article 110 is for "equipment" not conductors - - Article 490 also for equipment (Equipment, over 600 volts, nominal).


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