On Fri, 24 Jul 2009 15:50:08 +0100, John Rumm wrote:

PeterC wrote:
On Fri, 24 Jul 2009 11:26:53 +0100, John Rumm wrote:

PeterC wrote:
On Thu, 23 Jul 2009 22:12:49 +0100, John Rumm wrote:

PeterC wrote:
On Wed, 22 Jul 2009 16:03:14 -0700 (PDT), NT wrote:

So if I understand you correctly you also think equi bonding only need
be installed if and when electrical work is done. Note I say 'need
be', not 'is an option'.

NT

I would consider an electrical inspection (diy or professional) to be
electrical work. If the supplementary bonding is found to be missing (and is
needed because it is not a 17th edition installation) then the house
electrics are not up to standard and the bonding should be installed ASAP.

However I do not think that any authority can cut a supply to a house due to
a lack of supplementary bonding and people cannot be made to add the bonding
just because it is missing.

Adam
indeed... so there is no requirement.

Whether it ought to be fitted is another matter, one of opinion, and
the job is one which most households arent concerned about doing.
Given the near zero safety benefit I'd personally agree with them.
I took the bonding off the metal bath when I re-plumbed, as there's no
metal to/from the bath at all. The shower's on a RCD (nominally 30mA but
In which case the bath should not have been bonded anyway. As you say,
it just complicates the situation.

goes between 20 - 25mA) and if the shower were to become live there's no
path to earth anyway. If a fault develops and the RCD fails, I'd rather not
be the link beween 240V and a bonded earth!
The shower presumably has its own CPC from its supply circuit?
er, CPC? It's earthed back to the CU, if that's it.
Yup (CPC = Circuit Protective Conductor = Earth wire). The earth wire to
the shower ought to be included in any bonding that you do have. That
way if the shower goes faulty it will try and pull its earth toward
mains voltage, and the bonding will make sure that anything else the
room that you could touch at the same time will go with it. In your case
there may be little else to bond to - the CPC of the lighting circuit
perhaps and a CH pipes if metal.

It does not sound like a particularly high risk environment.

Thanks John.
The lighting circuit is only commoned on the bus in the CU, but even I
can't reach the switch or fitting. The rad. is way out of reach from the
bath but is next to the basin. The basin has no metal to it, the floor is
non-conductive, so if there were an earth fault and the RCD didn't trip any
bonding would just make the taps live whereas atm they're isolated.

The taps should not be included in the bonding anyway since they are not
connected to a conductor that leaves the room. (even if they had metal
tails for the first meter and then transitioned to plastic)

The simple way to analyse these things from first principles, is to ask
is "x" capable of bringing a potential into your equi-potential zone
(even if that potential it brings is that of the earth). If the answer
is no, then it does not want to be bonded.

As I said earlier, in your particular case you can make an analysis that
the fault scenarios that could lead to the bonding becoming decisive in
outcome are fairly obscure. (I can't think of many!). So you could argue
that skipping it entirely is unlikely to pose any significant risk, and
you can save some cash which you could now spend taping down the lose
carpet at the top of the stairs etc. However for completeness, it still
ought to be there on the grounds that additions/changes may be made in
the future - possibly by someone not aware of the trade off analysis you
have made.

Right, I'll check the CH, as that's the only part with copper.
There's an E tail by the stopcock but it's no longer connected - the
stopcock is the only metal there, as the supply is HDPE.
--
Peter.
The head of a pin will hold more angels if
it's been flattened with an angel-grinder.