|>Some fuses I've used were filled with sand to increase the interrupting
|>rating. The idea is that when the fuse melts, bits of sand would 'fall' in
|>between the melted ends and help interrupt the arc. If the arc got hot
|>enough, the grains of sand would melt together into a crude form of glass.
|>A small, 10A fuse of this type that measures just 2 1/2 inches long is rated
|>for interrupting 10 kA.
| Years ago, organizations such as UL and the National Fire Protection
| Association did studies on thousands of homes with fuses vs. circuits
| breakers. The bottom line was that the houses with fuse boxes were
| more likely to burn down in an electrical fire vs. the homes with
| circuit breaker panels.
I'd still feel a bit safer if I had protection on the main entrance by
both (with appropriate or excessive interruption rating, of course).
The question I've pondered is, if it is better to have the main breaker
first followed by the fuses, or have the fuses first followed by the
breaker. I suspect the former might be a bit safer than the latter as
it gives you an extra disconnect to completely de-energize the box when
replacing a fuse.
| Now that could be because the wiring was older in the fusebox homes,
| or the owners were so stupid that they were more likely to insert
| objects such as coins when they ran short of replacement fuses, etc.
Don't people get shock out of that?
I do know my dad has inserted the wrong size fuse, before.
| But, for the most part, if the circumstances are not right, it is
| possible for even the standard Edison-base safety fuses to explode
| during a severe short or overload and melt their holders. If the arc
| cannot be contained, wires can melt and damage can extend beyond the
| fuse box.
| Fortunately, this is rare... but it is also among the reasons that
| circuit breakers are considered the more modern and safe choice.
the only failure I've ever experienced of an OCPD is a breaker, not a
fuse. But my experiences are not statistically significant.
FYI, I do make sure all the breakers where I live right now (my dad's
house) get flipped off and back on at least once a year. The power goes
out often enough for that to be no additional inconvenience.
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
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