if i have 3phase circuit with conductors parralled 6 times per phase does that mean i have 6 raceways with 4 conductors each[3 hot 1 neutral] and when calcualating the neutral wire in light of 250-66 do we calcualate the sum of circular mill for hot conductors[where they have sixth of the ampacity]
parrallel circuit
- Thread starter kimrichi
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- Location
- New Jersey
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- Journeyman Electrician
Is this a feeder or service conductors?
does it make a difference
i know but just to understand a point
- Location
- New Jersey
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- Journeyman Electrician
A feeder does not always require a neutral.
let us say it is a service
- Location
- Lockport, IL
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- Retired Electrical Engineer
For starters, you don't calculate the neutral wire using table 250.66. That table is used to calculate the grounding electrode conductor's size. In the left-hand column, the title says to use the combined cross-sectional area of all ungrounded conductors. So you take the area of one of your phase conductors and multiply by six, and that is what you use to look up the required size of the GEC. "Ampacity" is not a participant in this process.
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- New Jersey
- Occupation
- Journeyman Electrician
If you have a Wye system you're required to bring the neutral along with the ungrounded service conductors. The minimum size would be found by applying T250.66 or for SEC's greater than 1100 kcmil it would be a minimum of 12.5% of the ungrounded conductors. This would apply even if there was no connected neutral load.
petersonra
Senior Member
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- Northern illinois
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- engineer
neither does a service
inspector141
Senior Member
- Location
- Westminster, MD
A grounded(neutral) conductor is required if the service is a grounded system. 250.24(C). The grounded conductor will return the fault current to the source due to a phase to ground fault.
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- New Jersey
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- Journeyman Electrician
True, but I assumed that we were taking about a grounded system since the OP said that he had " 4 conductors each[3 hot 1 neutral]".
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