Does IEC 62368-1’s Annex G.8 allow me to test the combination of varistors rather than individual varistors?
More specifically, you asked: By connecting two varistors in series I can manage the single fault criteria. Does IEC 62368-1’s Annex G.8 allow me to test the combination rather than individual varistors? Both G.8.2.2 and G.8.2.3 state a varistor or a surge suppression circuit containing varistors.
In response, some varistors and their surge suppression circuits will need to be subjected to overload and temporary overvoltage testing as explained in G.8.3.2 and G.8.3.3 of IEC 62368-1 Edition 2 and now in G.8.2.2 and G.8.2.3 of IEC 62368-1 Edition 3. Both IEC 62368-1 Edition 3 and IEC 62368-1 Edition 2 allow for the tests in G.8 to be performed on the circuit containing the varistor. Regarding single fault criteria, keep in mind, for some constructions as explained in sub-clause 5.5.7, a gas discharge tube (GDT) in series with the varistor is required. Thus, the opening or shorting may not be an issue. As this forum is not intended to analyze and provide guidance on specific designs, we suggest that you contact the UL office you work with and request a consult if you have a specific design or construction that you wish to discuss.