Anthony R. Gold wrote:
On Sun, 31 Aug 2008 15:42:14 +0100, John Rumm
wrote:

Anthony R. Gold wrote:

I am disappointed that my remark about plug fuses being needed in the UK
because of the use ring mains in the UK has turned into arguments over
whether any particular architecture is superior or unfit for purpose.
I was not arguing that one architecture is superior to another (I
believe there are pros and cons to both circuit types and one needs to
chose which to use based on circumstance). However I was questioning
your assertion that fuses are required *because* of the use of ring
circuits.

Easy to contradict - just find any examples of wiring codes that use ring
mains without fused plugs or any that use fused plugs on a radial system.

Well the second is easy, as I mentioned before, a 4.0mm^2 T&E 32A
radial, a standard circuit as described in BS7671.

Other countries don't tend to have comparable circuits since they don't
have plug fuses, and hence can't provide adequate protection for the
appliance flexes at the circuit origin.

To say that you can't find ring circuit designs that don't require plug
fuses seems to rather miss the point that the need for the fuse arises
out of the high current capacity of the circuit and not its topology.

Turn it round the other way, can you justify the need for a plug fuse
just on the basis of having parallel connection paths to the circuit
breaker? (or for that matter any other unique characteristic of a ring
circuit other than its high current delivery capacity)


--
Cheers,

John.

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