In message , Andy Wade
writes
Peter Ramm wrote:

Yes - thanks - but my point is that any current which passes from my
new CU to Henley block in a failure is already passing through 16mmsq
so anything I use of greater area and less resistance in series cannot
improve the situation. What am I still missing here?

Sorry, I read your first post in a hurry and didn't take that in - just
assumed is was 25mm^2 from the meter to the service connector block.
Nevertheless, new work should comply with current regulations and that
means using 25mm^2 tails throughout unless the assessed MD is 87 A or
less and there's no diversity applied at the CU (i.e. sum of MCB
ratings in the CU is also 87 A, which is unlikely).

In all probability you might well get away with 16 mm^2, but if the
main fuse really is 100 A then the installation does not comply with BS
7671 and there is a risk of the wiring overheating under overload
conditions. Why not install 25 tails now and then get the distributor
or meter operator company round to upgrade the bit twixt meter and
block at a later date?


Yep that's basically the approach I've taken, I could seen no reason to
not replace 'my' tails with 25mm^2 when I replaced the CU, I may try and
get the Dist co. to replace theirs as well.
--
Chris French, Leeds