Kedoades 1-14-2017
Hello, I am thinking of trying one of these black fuses. I see some people are recommending that you go one size up on the fuse, just wondering if this is always safe to do? thanks
Based on the several reports we have seen in this thread of SR Black fuses blowing when they shouldn’t, it seems clear that the unspecified "melting point" of SR Blacks is lower than that of typical stock fuses having the same current rating. ("Melting point" defines the combination of current and duration that if exceeded would cause a fuse to blow, and is expressed in units of amps-squared x seconds). Therefore it seems clear that if for example you were to substitute a "5 amp" SR Black for a 5 amp stock fuse you would in effect be substituting a fuse having a lower rating than 5 amps.
Also, from a technical standpoint it seems to me to be very unlikely that a fault in a component that should cause a fuse to blow would result in a current draw just slightly above the rating of the stock fuse. Especially in the case of a mains fuse, but most likely also in the case of DC rail fuses.
On the other hand, it might be argued that use of a higher fuse rating than stock could invalidate warranty and/or insurance coverage. But that too seems very unlikely. And in any event the same argument could be made even if the same rating as the stock fuse is used, just based on the fact that the upgraded fuse does not have approval from UL and other such agencies.
So IMO there is no problem going up one or two current rating increments. Although some others have expressed differing opinions earlier in the thread, and the post just above indicates that going up one or two increments may not always be enough anyway.
Regards,
-- Al
