In message <%wK6B.99198$***@fx36.am4>, Mike
<***@ntlworld.com> writes:
[]
Post by MikeMany appliances are protected from some causes of combustion by the use of
a fuse rated to allow normal use but only a small margin above this amount.
'Fridges and freezers have a much greater margin allowed as they are
subject to surges of a much higher magnitude so, allowing say 10% above
running demand is impractical; the fuse would either expire very soon after
starting use or weaken to the point of 'fusing' soon after this. Perhaps we
need a 'smart' anti-surge fuse in the line that could differentiate between
start up surge and abnormal demand lasting say several hundred milliseconds
or whatever.
I don't think I've ever seen a white good (fridge, freezer, washing
machine, ...) in the UK that had a fuse actually in the device itself,
though I'm sure _some_ do. Having said that, fuses do come in a variety
of types, from fast-blow to antisurge; antisurge ones will actually
tolerate a high current for a short time (how large and how short being
[a] partly a property of the fuse type, and [b] usually inversely
proportional).
However, the majority of large mains appliances, AFAIK, are just
protected by the fuse in the plug. (Which is really there to protect the
_cable_.) Fuses to BS1362 are available in at least 2, 3, 5, 10, and 13
amp. rating (which is the current they will _carry_ indefinitely, not
blow at) that I know of; however, (a) they're usually only available in
3 (red) and 13 (brown), with occasionally 5 (black), and (b) an awful
lot of people just put a 13A in all of them. There are very few
appliances - kettles, heaters, washing machines, dryers, and home
welders being about the only ones - that need more than 3A (that's
around 660 to 750 watts!); I doubt many even 'fridge/freezers need more
than 5A (over a kilowatt; if you're using that much, the room will get
hot!). In most cases, the cable itself won't happily carry 13A (in some
cases even 5A), and in more cases the contacts (e. g. in the plug)
won't, without getting decidedly warm.
Post by MikeHaving said all that, we once had a Phillips top-loader washing machine
that managed to heat up to an extent that the motor windings insulation
started smoking and the appliance scorched the floor tiles beneath it;
I'm _guessing_ that that was a matter of the motor itself being
overloaded - bearing stiff, or some piece of clothing got somewhere it
shouldn't. (_Could_ have been the heater elements stuck on or operating
without any water around them, but if the motor windings were hot, it
would most likely be mechanical load.) Not that it matters.
Post by Mikefortunately, I walked into the kitchen and could just see enough through
the smoke to isolate the appliance from the power in time to prevent a
serious fire.
The house stank for days after that!
Yes - I _don't_ like the smell of shellac in the morning ... (-:. One
thing to be said for the commonest insulation used on wire these days
(not motor windings, that's usually some sort of lacquer) - I think it's
PVC - is that it smokes profusely when hot, usually giving smell and
smoke as a warning.
--
J. P. Gilliver. UMRA: 1960/<1985 MB++G()AL-IS-Ch++(p)***@T+H+Sh0!:`)DNAf
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