On Tue, 01 Nov 2005 11:07:42 +0000 someone who may be Alex
wrote this:-

Would such a replacement bring any safety benefit? My "new" (30 years
old) has such fuses instead of circuit breakers, and I'm worried about
the electrical safety of fuses vs circuit breakers.

You need to split fuses into two, rewirable and cartridge fuses.

Cartridge fuses are moderately expensive, break high currents
rapidly and are moderately easy to replace.

Circuit breakers (of the sort we are talking about here) are the
most expensive, break moderate currents in time [1] and are easy to
reset.

Rewirable fuses are cheap, only break low currents and are fiddly to
replace.

For most houses circuit breakers are the most sensible form of
protective device. One of the few downsides is that, if the house is
near a substation, in some types of fault the circuit breaker will
fail to operate properly and the main (cartridge) fuse will operate.
Cartridge fuses guard against such problems, but cannot be reset.


[1] for many years now manufacturers have said that some of their
circuit breakers will break high currents as rapidly as a cartridge
fuse. However, the graphs they use to make these claims stop before
the interesting bits.


--
David Hansen, Edinburgh | PGP email preferred-key number F566DA0E
I will always explain revoked keys, unless the UK government
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