Its my opinion that your primary feeder for your 227kva transformer should be calculated as such:
227,000 / ( 1.732 x 480) = 273 amps
273 amps x 125% = 341 amp
341A next size up per 240.6 would be 350A breaker
So parallel sets of (3)#2/0 CU THHN/W @ 75 deg. would be ideal. The 400 amp breaker exceeds the maximum 125% as allowed in 430.3(b) for primary protection only.
Last edited by HTSR77; 12/15/12 12:53 AM.
