transformer Calculations

[xformer]

So for a transformer with Primary and Secondary OCPD, The primary OCPD is based upon the 125 % of the Primary Current with the option to go up to 250 % as permitted in the second half of of table 450.3(B) ? And if I increase OCPD must I then resize my primary conductors?

 

[david luchini]

Yes, the primary conductors must be protected by the primary OCPD. So increase the OCPD, increase the conductor size.

 

[augie47]

what David said !
Keep in mind Art 450 deals only with the transformer and it's protection/installation. As noted in the FPNs at 450.3, Art 240 still covers the OCP for the conductors.