Overcurrent Protection of Panelboard

[micaz]

I have a circuit breaker located in a service entrance panel that protects the porimary of a 480/120,208v 75kVA delta-wye transformer. The secondary of the transformer directly supplies a main lug only power panelboard. The service entrance panel, transformer & panelboard are located within the electrical room, with the secondary conductors from the Xmfr to PB not exceeding 10'. Article 240(C)(2) and table 450.3(B)have been met in that the secondary conductors do not exceed 10' & the primary overcurrent protection meets the 125% rule. However, Article 408.16(D)seems to overule everything by stating that secondary overcurrent protection shall be located on the secondary side of the Xfmr. I am confused!- can anyone please explain the logic?

 

[dpc]

There's an exception to 408.16(D) that references 240.21(C)(1) that covers this. BUT....

Make sure this is really a POWER PANEL and not a LIGHTING AND APPLIANCE Branch Circuit Panelboard. If more than 10% of the circuits are for lighting or appliances, it's not a Power Panel.

I'd put a secondary breaker or fuse in there somewhere, regardless of Code loopholes.