Fully agree with what could happen to a PC with 500Vdc to a PC but any PAT tester worth his salt will test all full voltage PC's.... having said that though if you are only testing the IEC lead then you are not fully ensuring the equipment has a correct earth bond, this should be an instant fail for a class 1 PC as you have only carried out half the test. Dependent on the PAT tester used, there should be the facility to reduce the current to 100mA for Class 1 IT Equipment, my Seaward has inbuilt preset tests which include the 100mA drop and has never popped a PC yet.
