On 27/04/2017 22:19, Tim Watts wrote:
On 26/04/17 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").


I have another POV on this. I can't quote chapter and verse as I do not
have my book to hand and my memory is ****e.

However, the 17th requires, IIRC, that any extraneous conductive parts
aka water pipes entering a bathroom/etc to be bonded to the main earth
as one of the conditions of not having supplementary bonding?

Yup the main bonding must be in place - so incoming services, and
extraneous metalwork that can distribute a potential around the building
(typically CH pipework)

g
So assuming the bonding is good and equally so across all such pipes
entering the bathroom, even without an RCD, the situation is hardly
worse than if supplementary bonding were present.

As far as I can see, all supplementary bonding does is keep it all
local, reducing the chance that it gets bypassed (eg plastic pipe
sections) or a local fault exists in the CPC to say the shaver socket.

It keeps it local, and also electrically short - so more tightly
controlled voltage differentials.

So SB makes for perhaps a more robust solution and one that *may* be
easier to verify[1] but 17th style if done correctly ought to be as
good, even if the RCD fails.


Thoughts?


[1] In reality, SB wires disappear under the floor and are often clamped
in inaccessible places like under the bath so how easy is it to verify
these, as opposed to just doing a loop test on all extraneous conductive
parts relative to the MET?

Although the loop test does not find the metal that does enter the EQ
zone, and could be made live by a fault, but is not bonded at entry (say
a partial metal pipe install where the incoming main and initial
pipework is plastic, and hence not included in the main bonding)


--
Cheers,

John.

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