ludwigbayer
Member
- Location
- North Eastern USA
We're installing a set of loads for a lab and were unsure of the requirements for neutrals in a 4 wire WYE setup.
There is equipment inside supplying a maximum (and controlled) amperage of 1100A in a WYE to a load, with four 3 phase sets of 4/0 going out of the building to the loads. The four loads then have their neutrals tied together internally and are tied to building ground thereafter as one. The loads are all in parallel.
The load on the neutral would be minimal, since it would potentially only carry the harmonic content of the output (max ~5%, or about 180A total).
If 250.66 is appropriate, then 3/0 is the maximum conductor I would need for this main neutral going to building ground.
But 310.15 is somewhat confusing here, and I could interpret it to say that I need to have a neutral here with ampacity for the full current capacity of all four loads (1100A).
Can someone shed some light on this for me? Thank you already.
There is equipment inside supplying a maximum (and controlled) amperage of 1100A in a WYE to a load, with four 3 phase sets of 4/0 going out of the building to the loads. The four loads then have their neutrals tied together internally and are tied to building ground thereafter as one. The loads are all in parallel.
The load on the neutral would be minimal, since it would potentially only carry the harmonic content of the output (max ~5%, or about 180A total).
If 250.66 is appropriate, then 3/0 is the maximum conductor I would need for this main neutral going to building ground.
But 310.15 is somewhat confusing here, and I could interpret it to say that I need to have a neutral here with ampacity for the full current capacity of all four loads (1100A).
Can someone shed some light on this for me? Thank you already.
