Two feeders, to two transformers, to one building

[FDSERICK]

I am working on a design for a customer that is primary metered. The service is located at the street and ran overhead to the main office building. They have a separate outbuilding with an existing 24.9kV-120/208V single phase transformer, feeding a disconnect for this building. This feeder comes off a riser that is fused on a single phase at the overhead line just outside of the building. The customer would like to retain the single phase transformer to serve the single phase loads, but they are looking into purchasing a loop feed, 24.9kV-480/277V transformer and pulling the single phase from the primary loop vs. at the riser.

They brought up the question, since this is technically not a service at this building: would they be able to retain the single phase transformer feed from the riser, and add a separate three phase feed from the same riser to the new transformer to "serve" the new three phase loads at the same building?

A loop feed seems to be the best direction in this case, but I don't have the answer to counter why they would not be able to leave the existing transformer as-is and run a separate three phase feed. This would be considered a second feeder to this building: would 225.30(B) from 2020 NEC apply? Does 225.30(E) apply due to "different characteristics", allowing the second feeder to come from the riser to the new transformer?

Any help is appreciated!

Thanks!

 

[don_resqcapt19]

You have answered your question. Three phase 480 is a different characteristic than three phase 208.
[/quote](E) Different Characteristics.
Additional feeders or branch circuits shall be permitted for different voltages, frequencies, or phases, or for different uses such as control of outside lighting from multiple locations.[/quote]

 

[FDSERICK]

You have answered your question. Three phase 480 is a different characteristic than three phase 208.

(E) Different Characteristics.
Additional feeders or branch circuits shall be permitted for different voltages, frequencies, or phases, or for different uses such as control of outside lighting from multiple locations.[/quote]
[/QUOTE]

Great! I suppose I needed to type it out to get my understanding correct. Thank you