On Mon, 10 Oct 2005 01:32:50 +0100, Andy Wade
wrote:

Rick wrote:

For where to run my wires,

They can be 50mm below the surface, in which case I can put them where
I like. Each room (except one, see below) will have at least one studd
wall, 100mm thick. This means I will need to put them in the
insulation layers, do I have to do anything special for this ?

You do need to ensure that cables don't become totally surrounded by
insulation (unless you've done custom circuit designs taking that into
account). If using the usual cable sizes you have two options: cables
can either be clipped along the studs or run in PVC conduit fixed to the
studs. For these methods and T&E cable the current ratings in columns A
& B of the following table apply:

Size Ratings in amps (ambient temperature 30 deg.C
mm^2 A B C conductor temperature 70 deg.C)
---- ---- -- --
1 11.5 12 16
1.5 14.5 15 20
2.5 20 21* 27
4 26 27 37
6 32 35 47
10 44 47 64
16 57 63 85

Key to columns:
A - in conduit in insulated wall (ref. method 6)
B - directly in insulated wall (ref. method 15)
C - clipped direct (ref. method 1)


In the other walls I can run the cables vertically from a "device", or
horrizontally between 2 devices in the plasterwork, which some plastic
protection - is this correct ?

Yes, and no protection is required for cables in these zones. For more
detail (illustrated) see http://www.niceic.org.uk/downloads/C5-43.pdf.

I intend to do each room, with a seperate run to/from the fuse box,

If you mean having a separate power (sockets) circuit for each room,
each with its own MCB, then yes, that's OK. If we're talking about
normal sized rooms then you could use 20 A radial circuits rather than
rings.

and two rings in the kitchen, one normal, one economey 7.

You mean one ring on a time-switched supply? That would be unusual, but
I suppose you could. I take it you're using storage heaters too
(otherwise the DNO or metering company wouldn't normally give you a
switched supply).

For my main room, I will have no studd walls, and no clear 100mm space
at the top, as that space if full of ceiling beams, and its too little
anyway. The plan is to put a wooden "trench" into the floor
insulation, and put the wires in this. I would then seal the top with
steel plate, which would be earth bonded. Is this OK ? I'd run the
"trench" round all the walls, and run the cables up to the devices.

I think that could be made to work, or you could use a proprietary floor
trunking system. Isn't there a floor void or roof space above where you
could run the cables and drop down to each point though?

Final problem, where can I put junction boxes ?

You shouldn't need any if wiring anew from scratch. Make all your
branches and spurs at wiring accessories, then the accessibility
requirement is met.

Can they go into the studd walls ?

Not normal screw terminal ones, if they're going to be plasterboarded
over. Crimped or soldered joints in a suitable enclosure are needed for
that.

HTH

Andy

Do you have a link on custom cable sizes, where the cables are totally
in the insulation, or can I simply use 2.5mm cable, and reduce the MCB
size. If I have a ring for each room, this would be fine by me, most
rooms will be bedrooms, studies, only the kitchen has lots of power
requirment.

Thanks
Rick