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	Subject - Secondary OCPD MN_EE I just found this site. Excellent discussion. Looks like a very knowledgeable crowd. I have a question (I am sorry if it has been covered elsewhere) about overcurrent protection of a secondary of a XFMR. 450.3 (a or b for now) seems to suggest that secondary overcurrent protection is not required if primary OCPD is 125%. However, 240.4 (a FPN sends you there) says if it is a wye secondary the overcurrent protection is required. So, which is it? My take is, that it is required, but the question remains, what size or what percentage? For example, a common installation might be a 225kVA – 480V- 120/208V that supplies a 800amp rated MLO panelboard with say (2) 400A and 3-4 225A. I think this is illegal. (450.3 also says something about the sum of the load cannot exceed the allowed value … again what is that allowed value?) Ryan_J 450 is for overcurrent protection of the transformer, not the conductors. 240.24(C) is for protection of the secondary condcutors, not the transformer itself. wareagle AS Ryan says, the transformer is protected buy 450 and the conductors by 240.24C 1 thru 6. Since you did not list the conductors, the answer to your question can not be given. Which of these sections complies with your installation?