In article ,
Mike Barnes writes:
In uk.d-i-y, John Rumm wrote:
The crux of the issue is that if you have a circuit capable of
supplying a current significantly in excess of the rating of the
appliance flex, then you need a overcurrent protected plug. So its not
really anything to do with the circuit being a ring or not, even if
that is the most commonly encountered 32A circuit in the UK.

I agree, but most of the world doesn't have fused plugs. So is there a
major problem with, say, those 3A flexes running to laptop power bricks,
plugged into a radial circuit limited to (say) 16A??

They have to be short, so they can pass the fault current
required to trip a 16A breaker. In practice, this doesn't
seem to be a problem. The only effect in the UK when our
appliances became subject to EU rules in this area was that
the lengths of such flexs are now limited to 2 or 3 metres.
When using a 3A fused plug, the limit on length was much
longer than was ever likely to be encountered.

Most appliances don't have a failure mode whereby they can
overload their flex, so there isn't a risk of running 15A
continuously through a 3A flex. The flex does have to handle
a fault current though (dead short), and pass enough current
so that the 16A breaker trips before the flex overheats.
This requires the flex resistance to be low, and hence the
limit on flex lengths.

The one item which completely screws up such design
considerations is an extension cable. These are routinely
available in lengths and sizes which are not intrinsicly
safe. Even if they weren't, people would still plug them
together to contrive to make them so.

--
Andrew Gabriel
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