transformer ques

[wireman1]

a step down transformer 480 volt 3 phase to 208/120 will feed a service panel .does panel have the option to be treated as asub panel a\or a servic panel being the transformer is a seperatley derived system .if treated as a service does it need another over current protective device besides the one protecting transformer cite articles thank you

 

[don_resqcapt19]

The secondary conductors will need to be protected per the rules in 240.21(C) and the panel itself per the rules in Article 408. The transformer primary OCPD cannot protect the secondary conductor or the panel in this case. You will also have to look at the grounding rules in 250.30.