Can anyone explain why 5 amp cartridge fuses used in Consumer Units are
so expensive compared to 5 Amp fuses used in plugs. Apart from the size I
cannot see what difference there can be in them . The two I bought today
locally ( Glasgow ) were 55p (each) but I have seen them much more
expensive than that .
"YESTERDAY is history,TOMORROW is a mystery,TODAY is a gift
Never had to buy one in 22years of owning such a CU .... but within a week
of changing it to a MCB type, one of the 6A lighting mcbs tripped when a
halogen mains bulb blew. I just wonder what fault current the fuses actually
would need to blow...
Fuses have a curve like MCBs without the instantaneous trip for short
circuits. They will certainly trip on the fault current caused by a short
circuited ionised blowing bulb. However, they need it to flow for more than
a few milliseconds, unlike an MCB.
BS1631 fuse has a much higher breaking capacity, as it's next upline
fuse is likely to be much high higher capacity than is the case for
a BS1362 fuse.
If you stick a BS1362 plugtop fuse in a consumer unit and then short
out the lighting circuit, the BS1362 fuse might not be able to break
the resulting high current flow, in which case the 100A main fuse will
be left to do so, which will wreck the lighting wiring and might cause
a fire (much more than 100A will pass).
Presumably one of the reasons is because there's not the same market for
them (not many needed compared with plug size and not the same competition
I'm assuming that size alone would also make a big difference to the cost.
In rural America, where trees fall down or line 'whips'
and linemen are many miles away, they use a novel
fusing system - a bank of three fuses in canisters.
When the fuse blows the canister explodes away
from the pole and pushes up the next fuse.
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