Dear Rich, I have seen many transformers in this business and always consider the core to be conductive unless it can be proven otherwise.
If you have doubts, check the conductivity with your hipot. The other route to take is to get a copy of the test report from the certification body. This should give you the creepage, clearance and drawings that will show you how the distances were obtained. Good luck Edward Eszlari TUV Rheinland of N.A., Inc Marlborough, MA
