On 18 May 2013 17:05, Sean Breheny wrote: > > It seems to me that it is not necessarily a good idea to put those two > fuses in series. In the scenario of a high voltage, high current capabili= ty > fault, what if the glass one opens first and arcs over but the resulting > arc limits the current to a level below that which will blow the HRC fuse= .. > That arc could last long enough to blast through the case of the meter. For some vales of necessarily :-). I suggested a value of say 10x higher - a 2.5A HRC fuse for a 250 mA glass fuse for a 200 ma current range. I don't have a good feel for practical values, but I suspect that once an arc gets established across where a glass fuse used to be that the effective resistance will be far far below the original fuse value. A fuse that will tolerate 2.5A will allow some very impressive melting down at main voltage - but if the glass fuse path starts to support anything like a lethal plasma arc I'd hope that the series HRC fuse would step in on its behalf. Maybe not. R --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .