On Wed, 19 Mar 2008 20:32:37 +0000, Andy Wade
wrote:
[with some snipped]
Fred wrote:

My set-up is meter switch fuse CU.

Let's call that switch-fuse 1 (SF1). Presumably it's there because the
house CU is some distance from the meter.

Yes.

If the output terminals in SF1
are big enough to accommodate two outgoing cables then you could split
at that point without the need for any kind of junction box - a tidier
arrangement.

Connect the CU tails and the T&E into the switch fuse if it will fit?
I had not thought of that.

If you do need to split after SF1 remember that Henley
blocks can only be used with single sheathed cable (6181Y)

As you can tell, I have only just started to think about this. I had
forgotten that one cable will be T&E not a "tail" cable (I presume
that 6181Y means a tail).

Whoa! "The cable" here is the 6 mm^2 that will run to the a second CU
in the garage? Before that you will need a 2nd switch-fuse (SF2) to
'fuse down' to (say) 30 A for the distribution circuit going to the
garage CU. Without SF2 your cable will only be protected by the fuse in SF1, which is presumably 60 or 100 A

Whoa indeed. Another refinement that I had missed in my initial
thoughts. I presume I could run single sheathed cable from the Henley
block to SF2 and the T&E from the other side of SF2 which would solve
my tail to T&E transition problem. I must confess I have not seen 30A
switch fuses; I thought they were 80A or 100A. I will have to pop to a
electrical trade counter.

There are two grades of PVC conduit, standard and heavy gauge
(most people use the latter), and there's steel. HG PVC would be fine
for a domestic garage, is fairly cheap, is quite easy to work with and
will give a tidy-looking job. Steel is obviously tougher, but involves
more of a learning curve to master the necessary skills to use it and
you'd have to hire bending and threading tools. Use PVC!

6 mm^2 T&E will go through 25 mm PVC conduit OK for simple runs with
only one or two bends. Don't even think about trying to use 20 mm.

25mm HG plastic it is then.

Your earthing arrangements? Remember that 6 mm^2 T&E only has a 2.5
earth (CPC), which may be too small. You may need to consider running a
separate 6 mm^2 earth for the distribution circuit.

I will have to check this. Thanks.