"John Stumbles" wrote in message
...
On Sun, 21 Sep 2008 15:03:16 -0700, jim wrote:

would earthing the existing metal conduit and thus not needing
RCDs be
a goer? Or have I missed something....

I think you'd have to guarantee that the conduit formed a good earth
for
its entire length so that when muggins blasts through it with his
electric
drill and contacts the live conductor it passes enough current to
earth to
operate the circuit protective device (fuse/MCB/whatever). Unless
the
conduit is substantial screwed steel that's unlikely to be the case:
most
conduit I've seen in domestic installations is rolled thin metal
sheet joined with similarly flimsy clamps at junctions, none of it
guranteed to give a good circuit.

--
John Stumbles

Fundamentalist agnostic

But John, the clamped conduit dates from the 50's & 60's. Normal steel
conduit supplied these days is fairly substantial but I admit rarely
installed domestically - I've put in quite a bit in semi comercial
situations (in my own homeworkshop ( hobby but rather extensive)) -
but I always run an earth (sorry CPC) conductor as well.

AWEM