Required amount of neutral conductors in single raceway for parallel feeder

[mpwasco]

I am planning to install a 500 amp parallel feeder to a panel using (2) sets of 500 mcm AL in one 4" raceway and will be reducing the neutral based on the present load in which (1) 1 o/t is capable of providing my ampacity. my question is...am I able to install just (1) neutral conductor or is it required that i install(2) neutral conductors as it is a parallel feed? any thoughts or code reference would be appreciated- thank You

 

[winnie]

There is no requirement that _different_ circuit conductors have the same characteristics. Phase A can be different from Phase B, Phase C, N.

The requirement for parallel conductors is that each 'composite conductor' be made up of 'sub conductors' that all have the same characteristics.

The 'sub conductors' must be the same material, the same size, the same length, etc.

One of the characteristics that you need to consider is what is in proximity to the various 'sub conductors'. So you can't have one parallel conductor in a conduit with a neutral and one in a conduit without a neutral. Or you can't have one parallel conductor in a PVC conduit and another in a steel conduit.

Of relevance to your installation, I think there would be a question of how the single neutral sits in the conduit in relation to the various phase conductors. If you simply have 8 wires (A,A,B,B,C,C,N,G) pulled into the conduit randomly, then I don't think you have a problem.

But if the conductors are somehow 'plexed' (bundled together on a single spool by a supplier), then some thought would need to be given to make sure that each 'sub conductor' in a phase was balanced in that bundle.

-Jon

 

[mpwasco]

There is no requirement that _different_ circuit conductors have the same characteristics. Phase A can be different from Phase B, Phase C, N.

The requirement for parallel conductors is that each 'composite conductor' be made up of 'sub conductors' that all have the same characteristics.

The 'sub conductors' must be the same material, the same size, the same length, etc.

One of the characteristics that you need to consider is what is in proximity to the various 'sub conductors'. So you can't have one parallel conductor in a conduit with a neutral and one in a conduit without a neutral. Or you can't have one parallel conductor in a PVC conduit and another in a steel conduit.

Of relevance to your installation, I think there would be a question of how the single neutral sits in the conduit in relation to the various phase conductors. If you simply have 8 wires (A,A,B,B,C,C,N,G) pulled into the conduit randomly, then I don't think you have a problem.

But if the conductors are somehow 'plexed' (bundled together on a single spool by a supplier), then some thought would need to be given to make sure that each 'sub conductor' in a phase was balanced in that bundle.

-Jon

thanks for your input

 

[infinity]

The neutral can be sized based on the calculated load so in this case a single #1/0 would be code compliant. Might not be the best design for a future load but it's code compliant nevertheless.

 

[don_resqcapt19]

Just remember that 215.2(A)(2) sets the minimum size for the feeder grounded conductor equal to that required for the circuit's EGC.

 

[mpwasco]

Just remember that 215.2(A)(2) sets the minimum size for the feeder grounded conductor equal to that required for the circuit's EGC.

thank you

 

[jaggedben]

I think the most salient point is that if you are planning to pull your two sets of conductors in separate metallic raceways then you need a neutral in each raceway.