Chris Maxwell asks: "Can anybody shoot a hole in this theory with a single fault condition?"
This subject has been debated before, on this list and elsewhere. Safety is always relative. In the scenarios you painted, Chris, the phase conductor always has an intact fuse after the neutral fuse opens. This can represent a risk of electric shock, by casual or intentional contact with the live circuit, to anyone attempting to replace the fuse that mistakenly believes the phase fuse is opened. Hence the service person warning requirement in 2.7.6 of IEC60950. Regards, Peter L. Tarver, PE ptar...@nortelnetworks.com
