Post by John HatpinMaybe I should have left this in the original thread. I'm
transferring Greg's reply here.
The socket isn't fused. There is a fuse (or breaker) at the
distribution panel for the house, with a dozen or so outlets on each
breaker.
Do you have the "ring main" system - a cable going around the outlets?
Typically here, we have a fuse (or breaker) for: downstairs sockets,
downstairs ceiling lights, upstairs ditto and ditto, etc.
No "rings". It's tree-shaped or a line. There is a central
distribution panel with fuses or breakers for wide areas of the house.
This sounds like what you describe. Each outlet has screws (or wire
grabber holes) for an input wire AND screws for a wire running to the
next outlet. I think you can also fan out several additional outlets
from that first one. But the line never loops back on itself.
There is never a breaker at the outlet, either inside it or in the
plug. Some expensive products like TVs, especially from the tube
electronics era, have a fuse in the product body, but never anything
at the plug or socket.
Sometimes the outlet is wired with a "ground fault interruptor", an
electronic circuit that compares the current out with the current
coming back to decide whether any current is missing (shorted to
ground). If so, it throws a breaker in the outlet. I don't know
whether the GFI also throws the breaker if there's too much current.
Like any other outlet, additional cheap outlets can be strung from the
one expensive GFI outlet - it will also protect the rest of the
outlets.
All outlets are rated to 15 amps (except for rare high-current
contexts) and the only smaller fuses you'll find are inside the body
of electronic items.
Post by John HatpinWell, the wire is rated at at least 15A (specific circuits such as
cookers excepted). 3000W/250V = 12A, so that's not a danger unless
you plug in a couple on the same ring, in which case the main fuse
will blow. I don't remember the ratings of the fuses in the main box,
but there are at least two types.
Our main fuses are 15 amps, but you often find people stealing a fuse
from the oven when something blows, so many are mis-fused with 20 amp
fuses. In the standard fusebox, all fuses are the same socket (same
as a standard light bulb) and the only difference is colour. A scheme
that used varying sized sockets for the various amp ratings came out
at about the same time as affordable breakers, but everyone went to
breakers, so I've only met the varying size fuse scheme once.
Post by John HatpinSo, say your 3000W electric heater develops a fault and starts drawing
increasing amounts of juice as it fails. Soon it's drawing 3300W,
which is more than 13A, so the fuse in the plug blows. All the other
appliances on the same circuit keep working: the TV, the lights, your
mother-in-law's life support system, etc. All you see is that the
heater stops working.
Sorry about the Mother-in-law. Here, they go to the kitchen range,
and steal a 20 or 30 amp fuse and swap it quickly into the fuse box,
promising to fix it with the correct 15 amp fuse later. They never
do.
Post by John HatpinSo, you unplug it and check the fuse. Actually, unless you're a geeky
type like me that has to have a multimeter, you're more likely to try
putting in a new fuse to see if that works. Soon enough, you know
that the heater's packed in, there's the Simpsons on TV, you can see,
and your mother-in-law is still breathing.
Logical, no?
There is still a cultural impasse happening here.
Everyone has stories about floundering around looking for a flashlight
to go down to the basement to flip a breaker or replace a fuse. We
accept that throwing a big chunk of the house into darkness when
something fails is "normal". It doesn't happen that often unless you
let your teen kid try to rewire radios or build "projects". My
parents had breakers and I knew which one would blow for each of many
outlets.
If I was being arrogant, I might think of the word "Lucas" from cars
and wonder if British electrical stuff was less reliable than ours,
but it's more likely just a cultural difference in whether dropping
half the house into darkness when the appl iance fails is acceptable.
Part of it is probably related to the fact that really high current
stuff is wired using a completely different plug to BOTH halves of the
wiring. Our home wiring scheme contains two opposite-phase circuits
referenced to one "common" wire. Standard outlets go to one side or
the other, mostly at random. Heavy duty outlets such as a water
heater, a range, a clothes dryer, or the pool heater go to both and
get 240 volts. With the really high-draw items removed from the
standard outlet, it may be easier to make them safe at our lower
voltage.
[the rest of your post is stripped as correct. Don't want to quote
anything that's right. Might just encourage rectitude.]
Post by John HatpinDisclaimer: John Hatpin doesn't know what the fuck he's talking about
when he gets onto electricity. He's probably wrong, but he's
interested to know exactly where he's making mistakes, and is playing
the Devil's Advocate to that end.
There. That's better. (grin)
--
Tomorrow is today already.
Greg Goss, 1989-01-27