Delta delta transformer

[Jpflex]

My boss has a 300 KVA delta delta pad mounted 3 phase transformer with 4800 volts primary and 480 volts secondary

When trying to size primary and secondary wire I used formula:

KVA divided by primary voltage x 1.732 for primary conductors

And

KVA divided by secondary voltage x 1.742

Therefore before derating factors or multiplying by 1.25 percent for continuous loads I got

Primary current at 36.08 amperes
Secondary current 360.85 amperes

My boss says local utility and google told him secondary current was 669 amperes and to use a # 4 aluminum conductor for primary

Which is correct?

And are you supposed to mark up conductor ampacity to 1.25 percent full load current value for continuous loads for commercial use?

Thanks

 

[augie47]

And
KVA divided by secondary voltage x 1.742 Actually 1.732 also (typo)

Therefore before derating factors or multiplying by 1.25 percent for continuous loads I got

Primary current at 36.08 amperes Yes
Secondary current 360.85 amperes Yes

My boss says local utility and google told him secondary current was 669 amperes No

and to use a # 4 aluminum conductor for primary You would select your OCP 450.3(A) and size your conductor to match the OCP device

Which is correct?

And are you supposed to mark up conductor ampacity to 1.25 percent full load current value for continuous loads for commercial use?

Thanks

 

[Jpflex]

Boss tried to say my figures were wrong because it’s pad mounted and commercial as if mounting style makes a difference