I have been supplied with an external hard drive unit, complete with
power brick and UK mains lead..
The mains lead has a 3 core 0.5mm2, marked U-2002 with a moulded 13A
unfused plugtop and 10A un-notched "kettle" plug.
Is this legal?
I was going to cut the plugtop off and replace it with a standard UK
plug, fused at 3A. But, with no voltage rating on the cable, am actually
wondering if it is rated at 240v..
Whilst asking here whether or not the supply of it was legally permitted.
If the cable assembly had been quite legal, then I would have considered
replacing the plug myself with a standard, fused, one.
As it is, the supplier has since apologised and is sending a replacement
cable to myself and other purchasers of this unit. He has asked me to
destroy the cable - which I will do on receipt of the replacement. Had
he asked me to return the cable at his expense, I would have done so.
Whilst I totally agree with you expecting a complying plug with a new
I think the whole thing is overplayed.
The UK plug must have by now used up most of the worlds brass, it is so
And no other country ,that I know of, has a fuse in the plug which is
only to protect a metre (39.37 inches for those who havn't converted
yet) of cable.
So technically there was no real problem even though it is illegal.
Did we determine what the law is wrt 'wall warts', which (as a rule)
don't have fuses? If they have some kind of thermal cutout or
non-replaceable fuse instead, what are the regulations on these?
And why would anyone make a mains lead with an unfused 13A plug?
(Much speculation on this thread, little fact.)
The reason the UK has a fused plug, is that we use a ring main for domestic
socket outlets. That is the supply is daisy chained from one socket outlet
to the next and then back to the 30A fuse (32A circuit breaker) on the
distribution board. Therefore all socket outlet in the ring share the single
fuse/circuit breaker protection. Most socket outlets are supplied as twin
13A wall mounted sockets, but due to the diversity, the overall load to the
fuse does not exceed 30A.
The system provides a very cost effective method of house wiring. Each plug
therefore incorporates a 3 - 13A fuse to allow the down sizing of the cable
connected to the plug and the matching of the fuse protection to the applied
The above tries to answer why the UK has fused plugs.
Before the introduction of the ring main and the 13A fused plug the UK used
similar circuit to those used by the rest of Europe, where each socket
outlet was rated at 15A and fused individually at the distribution board.
With an minimum of four 13A sockets per room throughout a modern home the
initial cost of the installation would far exceed the cost of incorporating
a fuse into a plug. The system also provides better protection to the user
as the installed fuse matches the applied load.
Regarding why anyone would supply a un-fused plug the simple answer is cost.
Product produced in the Far East are imported into the UK/Europe by
organisations who's only consideration is how can we maximise profit. They
do not normally have engineers who understand what the legal requirements
are in Europe, or engineers who are not allowed to test product for
compliance in Europe. They accept the suppliers assurances that they meet
European requirements. 80% of products produced in the Far East that are
tested in the UK by the company I work for fail to fully meet European or UK
requirements, unfortunately there is no legislation to force importer to
test products before they are offered for sale.
My recommendation to Sue is still that she should contact her local trading
standards department to ensure that the supplier does issue a recall, as
these plugs are dangerous when used in the UK or Ireland.
Interesting read. In the US, we have multiple outlets on one circuit (as a
rule, but there are exceptions for dedicated loads). The circuit protection
in the box is usually 15A or 20A. All wiring and outlets on a circuit must
be rated for the same current as the circuit protection (with one exception,
several 15A receptacles can be on a 20A feeder). Load diversity allows us
to plug a variety of 15A cords into multiple receptacles on one 15A circuit
breaker. One case where diversity doesn't work so well is kitchen counters,
so there is a requirement for kitchens to have at least two seperate
circuits for the countertop appliances (coffee maker, microwave,
Almost none of the plugs for appliances are fused here in the states.
Instead, all the plugs and cords are rated for 15A. I believe it's felt
that even 15A cords/plugs can handle 20A for a short time during a fault
condition should the appliance fail. With your larger 30A circuits, each
appliance cord would need to be rated for 30A without your individual
The one place I've routinely seen fused plugs here in the states is
Christmas decorations. Strings of lights are often offered with a plug at
one end and molded receptacle at the other so multiple strings can be 'daisy
chained' together. But the wire size used is not rated for 15A, so a
smaller fuse (<5A) is included in the plug. Sort of protects us from
getting too carried away with stringing too many lights in one long line.
As far as 'wall-warts', the ones I've torn apart (not very many) use such
small wire on the primary side, the things are self-limiting. If you short
the outlet wire, the internal impedance of the transformer is such that it
can't really draw much more than normal current. If the primary shorts, the
wire is so small it's practically a 'fusible link' in its own right. One
failure I've seen was exactly that, the thin wire from the brass prong to
the transformer had 'fused' leaving a tiny globule of melted copper on each
side of the break.
I thought he did a good job of describing a different system which
like the UK system probably has some good points and some bad.
Why are you so pompous.
This is an international discussion and everybody is entitled to their
And he never disparaged the UK system .
Because some limey cross-posted to alt.engineering.electrical :-). When
someone cross-posts to other groups, it is to a wider (hopefully still
related) audience. Ask the person that cross-posted why they included such
a wide audience. Maybe they *wanted* information on various
As far as 'inferior', I don't know about that. We don't need fused plugs
because we're smart enought to have all the equipment downstream of the
circuit breaker built for the rating of the circuit breaker. Whereas the UK
system seems to rely on additional protective devices for small equipment
not rated for the full circuit current.
Yes, our system is a lower voltage and thus draws more current for a given
load. But our circuits are wired in a 'star' sort of topology instead of a
'ring' bus, so which really uses more copper? Our system makes two
different voltage levels available.
This reminds me of something that was told me by a "Square D"
representative. I have no assurance as to its veracity. Square D decided,
sometime in the 60's to expand to the UK. Their eqipment did not sell well.
Finally they dragged out some old 1930 designs (the kind with cast iron
panel boxes with 47 bolts to hold the cover on) and sales skyrocketed.
In all truth, there are advantages and disadvantages to both the UK and the
North American approaches. Which is better is a moot point. What is known
for sure is that neither is going to adapt the other's approach. I do note
that, in terms of population served, the UK system is actually dominant- one
area where they outsold the US. I will not go into possible non-technical
reasons for this.
Don Kelly firstname.lastname@example.org
remove the X to answer
This is a good point. Each country made a decision in the late 19th
and early-to-mid 20th Century as to what type of electrical system
they would have and, for better or worse, we are each stuck with what
we have as a result of those decisions. Only minor and gradual
changes are permitted by code changes every few years, certainly
nothing that would have a drastic impact on electrical utilization.
My own take on it has to do with the relative wealth of the countries
involved and their access to inexpensive natural resources.
The US, in this case, has historically had the wealth and the
philosophy to spend the extra money on more wires, more copper, and if
necessary, a transformer for every house or a small cluster of houses.
This philosophy also allowed for increasing electrical usage
throughout the twentieth century. There was more of a tendency to
junk the obsolete 30 A fuse box services and eventually upgrade to 100
A , 200A and higher services. This is now a standard practice. There
is a more modern grade of service in the US because of the urban
sprawl in every city filled with new construction.
In Europe, perhaps from decades of being bankrupted from World Wars,
occupations (in some countries), and long periods of economic
stagnation elected to chose a system that appeared to be more
economical for the times.
The example I am familiar with would be a typical small town in
France. This would be one transformer serving the whole village at
240V, adequate power for lighting, washing, and basic human needs, but
not necessarily providing for big 60 gallon tanks providing a standing
reserve of hot water, central air-conditioning, swimming pool heaters
& filtration equipment, kitchens full of exotic electrical appliances,
Indeed, in France, you are not allowed to use too much power (that
Disjoncter again!) unless you pay the higher, more penalizing tariff.
Of course, France is a modern technologically advanced country, as are
most of the countries of Europe. Still, I think there are some basic,
but significant differences between the US and Euro electrical systems
in terms of capacity, convenience, and safety.
The switches date back to much earlier sockets on DC supplies,
where you had to switch off the current before pulling out the
plug, as just pulling out the plug alone doesn't stop DC from
flowing (you get a nice long arc;-). BS1363 sockets were never
designed for DC operation, but the switch had become expected
by then, so it's stayed. You can buy and fit sockets without
switches if you want to. There's certainly no regulatory reason
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