Sizing Neutral to point of grounding on 3 phase 4 wire system

[Spzr]

I am confused about section 220.61(C), regarding sizing the neutral in this particular application.
480 vac 3 phase 4 wire, with neutral to metering compartment only where it is dead-ended and grounded by the utility. We then have only 3 phase conductors and ground from metering compartment to our service entrance equipment with no neutral bus. We have a VFD, which constitutes about 50% of the load.
Since there is no neutral in our service panel and no loads connected to a neutral, I don't see how I can have any current in the neutral conductor from the meter can to the transformer. So it seems that this neutral could be reduced to 50% since it is not used.
Is this correct or have we missed something??

 

[petersonra]

I am confused about section 220.61(C), regarding sizing the neutral in this particular application.
480 vac 3 phase 4 wire, with neutral to metering compartment only where it is dead-ended and grounded by the utility.

We then have only 3 phase conductors and ground from metering compartment to our service entrance equipment with no neutral bus. We have a VFD, which constitutes about 50% of the load.

I think the N is required to be brought to the service equipment.

Since there is no neutral in our service panel and no loads connected to a neutral, I don't see how I can have any current in the neutral conductor from the meter can to the transformer.

I am inclined to agree there is no neutral current if there are no L-N loads.

Where you lose me is the can to transformer statement. Where does the transformer fit in? is this the utility transformer?

So it seems that this neutral could be reduced to 50% since it is not used.
Is this correct or have we missed something??

If it is under control of the utility they get to decide how big it is based on their own criteria.

 

[augie47]

250.24(C) requires the grounded conductor (on grounded systems) be brought to each service disconnecting means. The minimum size would be determined by 250.66 based on your phase conductors.