Andrew Gabriel wrote:

I would add that the above is true so long as the cable size does not
reduce from that of the ring. If you reduce the cable size (eg to
1.5mm sq), then a fused-switch unit is needed.

I was under the impression that so long as the cable used could safely
take the full 13A load then it was ok to reduce cable size on the spur.
1.5mm sq ought to be fine I would have thought.


The cable also has to be able to take the fault current (short circuit
to neutral or earth) for the time it takes the 30A fuse/MCB to trip
without overheating -- that's where a 1.5mm² cable is likely to come
unstuck (maybe literally;-) Also, it must still pass enough current to
blow the fuse within 400ms (IIRC).

Unless you are prepared to sit down and do the calculations to prove
that it's OK, stick with 2.5mm². And what are you saving anyway? peanuts.

Yup - quiet agree! I was only commenting that there is not actually a
requirement that you must not reduce cable sizes on the spur. Must admit
I tend to find very little use for 1.5mm sq cable!

--
Cheers,

John.

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