We are trying to upgrade a service from 1600amp to 2300amp using 5 existing 3" conduits. I would like to remove the existing 400kcmil conductors and pull in parallel 250's. I have 5 conduits. I would like to pull 2 each of the ungrounded conductors per conduit and one 250 grounded conductor for a total of 7 conductors per conduit. My calculated neutral current is less than 100 amps. Per code my thinking is that I would need only one 1/0 conductor per conduit for the neutrals. That would give me a total of 10 ungrounded conductors per phase and 5 grounded conductors total. The problem is that the local electrical inspector says I cannot downsize the neutrals because the NEC does not allow it and that there must be as many and they must be the same size as the ungrounded phase conductors. I also get the impression that they don't like parallel sets pulled in the same conduit. That will put me over on my conduit fill. I am reducing ampacity to 80% due to 6 current carrying conductors per conduit. I am not counting the neutral in this calculation. I really don't want to dig up a parking lot and add 2 more conduits. Is my thinking in error? Thanks.
