On 23 Jul 2004 18:47:04 GMT, Ian Stirling wrote:

Tom B wrote:
On Fri, 23 Jul 2004 16:08:12 +0100, "Christian McArdle"
wrote:

Yes, the bathroom is involved, so I'll bond. I presume I'll need 10mm
earth
wire?

For supplementary bonding, I'd only bridge the Cuprofit if it is installed
inside the bathroom. Otherwise, just supplementary bond the section within
the bathroom to all other fittings that require it, but leave the external
Cuprofit unbridged. Ideally (which is not possible if there are electrical
fittings or other continuous earthed services) the supplementary bonded
metalwork in the bathroom will be connected to each other, but not earth.
This makes everything in the bathroom at the same voltage, but without
providing a low impedence path to earth. Of course, it is rarely possible to
achieve without plastic plumbing.

Christian.

Errrr... I must be missing something here. What is the point of connecting all
the bits of metal together but not to earth? This doesn't "make everything in
the bathroom at the same voltage". It just makes them all 'floating', just the
same as if you leave them individually 'floating'.

If all the metalwork/water is at the same potential, then there is no
possibility of getting across two individual appliances, one of which
has a fault, causing it to be live.

Then again...

No, No, No... If all the metalwork/water is at the same potential then there is
no fault and therefore no problem! :-)

If an appliance earth fails AND the case becomes live then touching it while
touching another good earth is likely to give you 50 cycle flutter of the
eyeballs. Earthing lots of otherwise 'floating' bits of metal in the vicinity is
more like to enable this to happen rather than less.