On 25/04/2017 13:27, John Rumm wrote:
On 25/04/2017 12:16, Adam Funk wrote:
On 2017-04-22, John Rumm wrote:

On 22/04/2017 10:50, Ivor Nastychestikov wrote:

Firstly, no such thing as "earth bonding" - the phrase makes no sense.

You can have earthing, and you can have equipotential bonding. Two
different systems that work in different ways and are designed to
provide shock protection by different mechanisms. (reduced shock
duration for earthing, and reduced shock magnitude for EQ bonding).

But they're both done with green & yellow striped cable!

Hence why they call it a Circuit Protective Conductor (CPC) and not an
"earth conductor"

You have what are classed as "fortuitous effects"; in that equipotential
bonding (by inclusion of multiple CPCs) may also lower the earth
impedance at the point of a fault and hence improve disconnection times.
Likewise earthing may add additional conductors that will also function
as eq bonding, and hence lower the touch voltages.

However these effects (while not unwelcome) may not be relied upon[1],
and each system needs to function independently.

[1] e.g. your main eq bond to the incoming water main may provide a good
additional path to earth. However it would be unwise to rely on that as
an earth since the water supplier may change it to plastic etc. So when
testing your main earthing terminal, you disconnect any bonding
connections to it for the duration of the test. Likewise eq bonding
conductors in a bathroom, don't actually need any connection back to the
main earth terminal to function correctly.




I have said it before, and I'll say it again.

Bathroom electrics will one day need supplementary bonding fitting again.

RCDs are not good enough.

--
Adam