Feeder Neutral sizing

[Hvactrician]

I currently have a building that is being fed with a 400 amp 480/277 service. We are running new feeders from a different service in a connected buildingto the building to allow for excavation and construction. We are running a four wire circuit of 480/277 and changing the fuses to 200 amp. The only thing that the service is feeding is a 277 V lighting panel with balanced lighting loads and two 480v -120/208 transformers. our current carrying conductors are 4/0 what size do I need for my neutral?

 

[wwhitney]

The larger of (a) the minimum size for the calculated neutral load for your feeder (which would be the full load on the 277V lighting panel if I understand the loading correctly) and (b) the minimum size for an EGC for your feeder (see 215.2(A)(2)).

Cheers, Wayne