On 27/04/2017 20:35, Roger Hayter wrote:
John Rumm wrote:

On 26/04/2017 10:58, Adam Funk wrote:
On 2017-04-26, John Rumm wrote:

On 25/04/2017 21:45, ARW wrote:

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.

It has to be said that something that relies on a passive length of wire
and some pipe clamps is likely to be more reliable than something that
needs working electro mechanics.

I'm struggling to imagine how it could do any harm to have more
bonding than required, as long as it's sound (i.e., not connected to
anything "bad").

Depends on your definition of more than required... if you mean
including bonding in a bathroom which meets the 17th edition exception
and hence could in theory do without, then yup no harm, and not expensive.

However some places take it to the extreme and festoon every bit of
pipework with bonding cables in places where there is not an elevated
shock injury risk. In those cases, there are probably other things you
could do with an installation to get a better return on the investment.

My house was wired (presumably not by a professional) with 10mm^2
green/yellow wire parallelling all the T&E circuits from the CU
branching repeatedly with connection to all the pipework in every
room. Since it is all surface wiring (for structural reasons) in boxes
and trunking of various kinds I tend to strip out great reams of it
every time I redecorate or alter anything. As all circuits (except the
economy 7 one) are fast 30mA RCD protected it is hard to see what the
objective was, but it seems to imply a confusion between bonding and
circuit protection. Most of the rooms have no locally unearthed
metalwork in them apart from the central heating, which is all copper
anyway. For reasons which seem arbitrary, even earthed electrical
fittings (such as outside lights) seem often to have a parallel 10mm^2
earth connection back to the CU.



Perhaps someone read this and got confused.

http://electrical.theiet.org/wiring-...g.cfm?type=pdf

--
Adam