Re: Music for Sysadmins...



On Mon, 12 Nov 2007 14:51:55 -0500, Graham Reed <greed@xxxxxxxxx> wrote:
Jasper Janssen <jasper@xxxxxxxxxxxx> writes:
Are you allowed to touch the main fuse? Here the main fuse is between the
powerco wiring and the meter, and for that reason it's very much sealed
from tampering. Blow it and you're looking at 50 euros or so for the
powerco to come by and replace it.

Hmmm. NA-ian fuse panels have the "main" fuses between the master
switch and the bus-bars that feed the fuses that feed the branch
circuits. That's all on the load side of the meter.

Breaker panels work much the same way, except the master switch _is_
the breaker... which means you'd better call someone competent if the
main breaker fails, as you're dealing with Rich Chunky Amps and no way
to turn them off.

I've watched competent electricians do that sort of thing, and it's not
*hard*.. just something that you absolutely have to get every single step
in sequence right. Although NA-ian breaker/fuse boxes are very scary
inside, with those busbars. Ours are generally wired with insulated wire
rather than exposed busbars, and if there are exposed busbars they're a
lot smaller and more localised.

In our case though it's not that hard to get the stuff switched off, you
ask the powerco to come round, they snip the seal, unscrew the main fuse
holder, reseal, you can putter to your heart's content after the meter,
and then you call them to come and hook you up again. That's the theory,
at least. It's not entirely cheap, though.

I've never been a party to a main fuse blowing, but they look like a
beast to get out. Big honkin' copper tabs sticking out of each end of
the fuse cylinder.

Ours are just uprated versions of our regular fuses. Standard fuses, back
in the day (and of course on many many legacy installations) look like
this: http://nl.wikipedia.org/wiki/Afbeelding:Smeltveiligheid.jpg . That
particular size holder, thread, and fusebody can be used for IIRC
6/10/16/20/25 amp fuses (possibly 4A?). Each size fuse has a different
size neck contact, with standardised plugs inside the panel this lot
screws into that prevent you from inserting a higher rated fuse than the
thing's meant for (unless you change out the plug).

The mains fuses were the same thing except one size larger, accepting
something like 25/35/50 and some others.

These days the smaller circuit protectors are pretty much universally
breakers, and main fuses can be installed in new installations either as
fully sealed fuses of the type above *or* as breakers where you're allowed
to turn them off and back on, but not touch the other bits. The latter is
of course vastly useful and thus it's nowhere near standard.

Jasper


.



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