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.
I presume I change this to: meter switch fuse henley blocks cu
(house) and cu (garage)
I've never used henley blocks before; is there any advantage to using
two SP blocks or one DP block?
You might not need the Henley blocks(s). 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. If you do need to split after SF1 remember that Henley
blocks can only be used with single sheathed cable (6181Y), unless
mounted in some sort of enclosure. (I'd use a DP block, unless there's
any good reason for preferring 2xSP ones.)
The cable will exit the house under the stairs [...]
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. A 1-way Wylex unit fitted with a 30 A BS 1361 cartridge
would be a suitable choice for this. Without SF2 your cable will only
be protected by the fuse in SF1, which is presumably 60 or 100 A for the
house.
[...] into the garage (no underground or overhead runs required) but
because it will exit at about 1.5m above floor level, it will be at a
height that it might get knocked by people or cars, so I think I
should protect it in conduit.
OK. You haven't said anything about what circuits and equipment are
going into the garage, but it might make sense to do the whole of the
garage sub-installation in conduit. If all the wiring is enclosed you
could wire in 'singles' which is much easier to use in conduit than T&E.
Are all conduits created equal or are some better than others?
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!
How thick is 6mm^2 T&E, does it require "fat" conduit? of course,
IIRC conduit will reduce the max load the wire can carry.
Sizes and ratings here
http://www.wiki.diyfaq.org.uk/index....es#Cable_Sizes
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.
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.
HTH
--
Andy