Transformer calculation

[arsln69]

Hello Mike
I was watching your transformer calculation video about 45kva transformer secondary overcurrent device it was 175a and 2/0 wires

Question: If I put 200A breaker and install 3/0 wire would it be safe

 

[augie47]

Mike seldom posts here, so you have to depend on your peers to offer their opinions.

When dealing with transformers you must keep in mind you have to comply with at least two Code sections: Art 240 and 450.
If you comply with the conductor rules in 240.21 your 3/0 conductors will be protected by you 200 amp breaker so you are fine there, however, you have exceeded the 125% secondary rule from Art 450 so your 200 amp secondary protection would only be allowed if the primary protection met the 125% rule.