"NT" <(E-Mail Removed)> wrote in message
news:21380a13-f247-4cd7-8dec-(E-Mail Removed)...
John Rumm wrote
NT wrote

>> Whether it ought to be fitted is another matter, one of opinion, and
>> the job is one which most households arent concerned about doing.

> Which only demonstrates that many of them are poorly informed about
these things.

One could certainly argue that. But I think the average householder is
well aware that on their list of priorities its extremely low, and in
safety terms theyre quite correct on that point.


>> Given the near zero safety benefit I'd personally agree with them.

> I am not sure why you consider this to be of "near zero safety" benefit.

The near zero number of resulting deaths. When you compare the spend
per benefit of equi bonding to many other measures one can take, it
simply ceases to be a path worth pursuing unless one is for some
reason obliged to do so.


> It is equal I would say to having no RCD protection on a outdoor power
feed.

Unless I'm mistaken, the level of fatalities don't agree with that
claim.


> It is after all the greatly increased risk of severe shock imposed
> by the surroundings that make the RCD protected supply desirable. Same
> applies in a bathroom.

But that is an incorrect way to assess safety. There is no end of
things that could happen, what matters is which ones do and how often.


On Jul 23, 12:33 am, John Rumm <see.my.signat...@nowhere.null> wrote:
> NT wrote:
> > On Jul 22, 5:34 pm, "ARWadsworth" <adamwadswo...@blueyonder.co.uk>
> > wrote:
> >> "NT" <meow2...@care2.com> wrote in message
>
> >>news:87164220-b039-4f01-b206-(E-Mail Removed)...
> >> On Jul 21, 6:01 pm, John Rumm <see.my.signat...@nowhere.null> wrote:
>
> >>> NT wrote:
> >>>> On Jul 21, 1:33 am, NT <meow2...@care2.com> wrote:
> >>>>> On Jul 20, 2:57 pm, John Rumm <see.my.signat...@nowhere.null> wrote:
> >>>>>> NT wrote:
> >>>>>>> This article could do with input/suggestions:
> >>>>>>>http://tinyurl.com/mewmhe
> >>>>>>> or
> >>>>>>>http://wiki.diyfaq.org.uk/index.php?...trics#Suppleme...
> >>>> The article is now edited to read
> >>>> "Unless an installation complies with the latest requirements of the
> >>>> 17th edition... then supplementary equipotential bonding is
> >>>> required."
> >>>> Are you saying that there is a requirement to bring all existing
> >>>> installations into line with this? I'm not aware of any requirement
> >>>> to
> >>>> do so.
> >>> Yes, but I think you are misinterpreting the sense of "required" to
> >>> mean
> >>> something that building regs or some other authority say you must do
> >>> now.
> >>> The "requirement" is a technical one from BS7671. There is no *legal*
> >>> obligation to install missing bonding (unless you a changing something
> >>> electrical in the room anyway, when one might argue that part P would
> >>> make it so).
> >>> However, to wire or alter a room containing bath or shower then one
> >>> *may* be required (for reasons of complying with BS7671 and for best
> >>> practice / good workmanship) to install or upgrade bonding. I use the
> >>> word "may" since the 17th edition is the first version in recent times
> >>> to offer an alternative to installing bonding.
> >> Sounds like we agree on the principle, but differ on the wording. I
> >> wanted to try and clarify it in the article as its a much
> >> misunderstood area, and many people sent into a tailspin over nothing,
> >> or paying out for work that doesn't need doing.
>
> >> So in short there is no real world requirement for such bonding to be
> >> retrofitted to existing wiring unless electrical work is being carried
> >> out, in which case the end result should be regs compliant.
>
> >> I propose adding a sentence to explain that, probably much further up
> >> in the article since it affects most of it.
>
> >> NT
>
> >> Hi
>
> >> The lack of supplementary bonding would be flagged up on a PIR if the
> >> wiring
> >> was to the 16th edition. However the lack of RCD protection for cables
> >> behind plaster would also be flagged if the system was installed to the
> >> 16th
> >> edition.
>
> >> The main difference is that the the lack of supplementary bonding would
> >> be
> >> code 1 (requires immediate attention) and the lack of RCD protection
> >> for the
> >> cables would be code 4 (does not comply with BS17671:2008).
>
> >> I would suggest that supplementary bonding "when required but not
> >> present"
> >> should be installed ASAP regardless of any proposed electrical
> >> installation.
> >> As John pointed out, any installations are part P governed and so would
> >> need
> >> the supplementary bonding to be installed.
>
> >> The other point to note is that any alterations to bathroom or kitchen
> >> electrics also need the main equipotential bonding to be brought up to
> >> current standards when the work is carried out.
>
> >> A mixture of RCD protected and non RCD protected bathroom electrics
> >> still
> >> need supplementary bonding. eg a split load 16th edition install with
> >> the
> >> bathroom lights non RCD protected and then an electric shower is added
> >> to
> >> the RCD side. Supplementary bonding must be fitted between the lighting
> >> and
> >> the shower.
>
> >> HTH
>
> >> Adam
>
> > 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'.
>
> I think there are two things at issue here:
>
> One is semantics - yes you could argue that if you are changing nothing,
> then installing bonding is not "required".

Thats a true fact, not semantics

> However, if no change is
> being made or contemplated, why refer an article on bathroom electrics
> in the first place? Chances are if you are looking for information on
> this, then you plan to make some alterations, at which point this work
> becomes required.

Many times people get a PIR done that says you need to fit equi
bonding, and they mistakenly believe it to be so. Our article should
tell them the truth, that there is no requirement to fit it unless
youre carrying out electrical work.

Theres nothing wrong with also adding a section of whether we think
you should, but I dont think we ought to tell porkies by saying yes
you're required to do it.


> Also if we are addressing competent DIYers seeking to
> improve bad things on their electrical system, then encouraging them to
> add bonding when its required but missing, is a "good thing" IMHO. Its
> cheap, easy to do, and depending on the circumstances can make a life or
> death difference should you be unlucky enough to have something go bang
> unexpectedly.

So opinion is mixed. If, as we did once before, guess the average cost
of installing it, multiply by the number of houses, and divide by the
number of lives it saves per year it works out at a phenonmenally high
price per life, when many other simple domestic works for the same
money/time would yield far greater safety improvement. It just isnt
warranted on safety grounds.

Why not...

Lets say install cost £20 materials, 4 hours labour for a diying
novice, including going and getting the bits.
Total cost £20 + 4x7-15, perhaps £40 as a balpark figure
= £60 total

x20 million houses = £1.2 billion

If this saves one life every 5 years, thats a cost of 6 billion per
life saved, which is orders of magnitude higher than a whole swathe of
more practical constructive measures one can take.


> Secondly, there is the issue of severity. I expect based on comments you
> have made in the past that you don't consider the lack of "required"
> bonding to be of particular concern. However as I see it (and as Adam
> highlights, as any form of proper inspection would see it), it is
> classed as a fairly severe fault.

That only shows a recognised flaw in such testing, namely that the
results given are sometimes entirely unrealistic and to encourage
needless spending.


NT

Hi


I do not accept that there is a flaw in a test procedure that correctly
identifies a fault an electrical installation.

The Wiki article on bathroom electrics does have a link to supplementary
bonding requirements and that is good.

Maybe the words

"Unless an installation complies with the latest requirements of the 17th
edition then supplementary equipotential bonding is required."

could read

"Unless an installation complies with the latest requirements of the 17th
edition then supplementary equipotential bonding should be installed to
BS7671 regulations if you ever want a pass certificate on your house
electrics when you want to sell your house and do not want the buyer to
start knocking money off if the buyer is looking for faults"

or

"Unless an installation complies with the latest requirements of the 17th
edition then supplementary equipotential bonding should be installed to
BS7671 regulations"

For some reason there seems to be far much trouble caused by using the word
"required".

Adam

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.
--
Peter.
The head of a pin will hold more angels if
it's been flattened with an angel-grinder.

NT wrote:

> [...]
> Given the near zero safety benefit I'd personally agree with them.

Here's one recent case where the benefit of some supplementary bonding
would have been far from zero:

http://news.bbc.co.uk/1/hi/england/cornwall/8140632.stm
http://www.telegraph.co.uk/news/ukne...bath-taps.html
http://www.dailymail.co.uk/news/arti...-new-home.html

--
Andy

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.
--
Peter.
The head of a pin will hold more angels if
it's been flattened with an angel-grinder.

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.

On Fri, 24 Jul 2009 21:17:42 +0100, John Rumm wrote:

> PeterC wrote:
>> 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.
>
> Is the rest of the house metal or is that plastic as well?

The water is plastic and the CH metal.

It all used to be bonded back to the incoming water pipe, but that was
renewed, then I had a combi and the HW pipes didn't like the pressure so I
replumbed in plastic.
There's no earth AFAIK except for the CU. It is, ISTR, PME.
--
Peter.
The head of a pin will hold more angels if
it's been flattened with an angel-grinder.

On Jul 23, 8:23*pm, John Rumm <see.my.signat...@nowhere.null> wrote:
> NT wrote:

snip

If I get the time I'll address some of the confusion here


NT

On Sat, 25 Jul 2009 01:04:27 +0100, John Rumm wrote:

<snip> as me mouse wheel is overheating

>>>>> 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.
>>> Is the rest of the house metal or is that plastic as well?
>>
>> The water is plastic and the CH metal.
>>
>> It all used to be bonded back to the incoming water pipe, but that was
>> renewed, then I had a combi and the HW pipes didn't like the pressure so I
>> replumbed in plastic.
>> There's no earth AFAIK except for the CU. It is, ISTR, PME.
>
> How does the gas get into the place? (assuming its a gas boiler - same
> question but for oil if its one of those). It sounds like you may be
> missing a main bond to that.
>
> It sounds like the CH pipes are the only ones that can do much mischief
> then, since they probably romp all over the house carrying a potential
> potential with them ;-)
>
> (imagine a fault in the boiler leaving the pipes live etc)

Gas is via plastic pipe to the meter on the front wall then copper to the
boiler. It has no connection to it in the box.
This means that the house has no earth other than the CU. Here it looks as
if there's an E bonded to the SWA and connected to the CU and to the
incoming N.

If the pipes were to become live, at least the rad. in the bathroom
wouldn't be to dangerous as there's no other reachable earthed place to
touch - it'd need the pull switches to have their covers off or, at a
stretch, the fan heater (I could reach that but most people couldn't).
--
Peter.
The head of a pin will hold more angels if
it's been flattened with an angel-grinder.

On Jul 23, 8:23*pm, John Rumm <see.my.signat...@nowhere.null> wrote:
> NT wrote:

> >> I think there are two things at issue here:
>
> >> One is semantics - yes you could argue that if you are changing nothing,
> >> then installing bonding is not "required".
>
> > Thats a true fact, not semantics
>
> Not really - the wiring regs still say its required. The fact that there
> is no legal compulsion to update the exiting install to follow those
> requirements does not make the requirement go away.

it means that, by definition, it isn't required for most houses.

There is simply no requirement for most houses to be to current
standards, and the great majority aren't.



> We could include extra verbage at the top that highlights what is meant
> by "required" etc, but then why single out this article?

You removed the statement that it was required if doing electrical
work, replacing it with the erroneous claim that its required in all
cases.


> >> However, if no change is
> >> being made or contemplated, why refer an article on bathroom electrics
> >> in the first place? Chances are if you are looking for information on
> >> this, then you plan to make some alterations, at which point this work
> >> becomes required.
>
> > Many times people get a PIR done that says you need to fit equi
> > bonding, and they mistakenly believe it to be so. Our article should
> > tell them the truth, that there is no requirement to fit it unless
> > youre carrying out electrical work.
>
> PIRs don't include an in depth analysis of the implications of things
> like missing bonding. In some cases you could argue that a particular
> installation has very few if any failure modes where EQ bonding would
> mitigate. Equally however, there may be some that make it very well
> worth having.
>
> By all means tell em that they are not legally obliged to carry out the
> work; but if the PIR has highlighted a fault that should be fixed,
> unless they are in a position to carry out enough analysis to say if
> there is a better cost benefit trade off to be had elsewhere, they ought
> to carry out the fix.

There is simply no basis for saying the missing bonding should be
fixed. The cost/benefit analysis shows it to be at best worthless, and
the legal position is that it is not required in most cases.


> Any other advice would be reckless.

Telling the truth about the legal position is not reckless or unwise.


> A couple of example scenarios:
>
> e.g.
>
> 1) 16th edition PMR head end, small shower room, plastic pipes
> everywhere and the only electrical circuits in use are the lighting one,
> and a spur from a upstairs ring circuit to feed a towel rail. The lights
> are SELV downlighters. The actual risk of serious shock in this
> circumstance is negligible. Since mains never manifests in the room
> anywhere other than the towel rail, and there are no other extraneous
> conductive paths (the CPC of the lighting circuit does not present in
> the room - the metalwork of the down lighters is floating, the switch is
> non conductive and out of reach on a string). *According to to the Regs
> Bonding is still required, however the implications of ignoring the
> requirement are to all intents nil as things stand.
>
> 2) 15th edition install, re-wireable fuses, TT head end (overhead wire
> supply), no bonding at all (main or supplementary), a VO ELCB is
> connected inline with the main earth provided by a gas pipe. There are a
> number of borrowed neutrals and neutral earth faults. a 13A socket is
> installed beside the sink to allow a hairdrier etc be plugged in.
> Bathroom has CH piped towel radiator, metal pipes to all taps and
> cistern, and an electric shower, plus fan heater, and some class 1
> luminaries on a low ish ceiling controlled by a nice polished chrome
> wall switch next to the shower. In this case there are any number of
> fault scenarios that could present serious and life threatening shock
> hazards i.e. faults that could leave high touch voltages on metal
> surfaces for extended periods, with ready access to an independent earth
> close to hand. Now obviously a PIR would highlight all manner of
> shortcomings here. The long term solution would probably be a package of
> measures including a re-wire or at least a new head end. However
> installing main and supplementary bonding PDQ would be cheap and
> effective way to lower the rooms status from "death trap" to something
> more acceptable.

You're missing the point I made last time. You may /imagine/ some
unbonded bathrooms to be deathtraps, but the figures (ie facts) show
very clearly that they're not.



> > Theres nothing wrong with also adding a section of whether we think
> > you should, but I dont think we ought to tell porkies by saying yes
> > you're required to do it.
>
> Depends on your interpretation of required. See comments above.
>
> >> Also if we are addressing competent DIYers seeking to
> >> improve bad things on their electrical system, then encouraging them to
> >> add bonding when its required but missing, is a "good thing" IMHO. Its
> >> cheap, easy to do, and depending on the circumstances can make a life or
> >> death difference should you be unlucky enough to have something go bang
> >> unexpectedly.
>
> > So opinion is mixed. If, as we did once before, guess the average cost
> > of installing it, multiply by the number of houses, and divide by the
> > number of lives it saves per year it works out at a phenonmenally high
> > price per life, when many other simple domestic works for the same
> > money/time would yield far greater safety improvement. It just isnt
> > warranted on safety grounds.
>
> Statistical exercises like this can be useful for setting government
> policy[1]. However we are not really concerned with overall impacts,
> targets, costs to the nation etc, and are focussing on one electrical
> installation. What is best for the majority has no bearing on what is
> best for Joe Internet Searcher, 32 Acacia Avenue who has just moved into
> a place and had a PIR

it seems evident that cost/benefit is relevant, and is in fact
precisely the grounds on which we make decisions as to what to spend
on safety.

Lets take an example: imagine you have 2 options, to spend £60 on
getting the car's brakes fixed or to spend on equi bonding. You know
that there are around 3500 deaths per annum from car crashes, and
around 0.2 from bathroom electrocutions. In each case spending the £60
would decrease those risks, but not to zero. Its obvious what one
would choose, the question is how? If you don't think its on cost/
benefit ratio, on what basis do you make the choice?


> throw up reams of faults that he does not
> understand; missing bonding being one of them.

If there are reams of faults, a rewire would be a lot more sensible
than fitting equi. And if Joe were too broke to do that, spending the
money on fixing some faults would be far more worthwhile than fitting
equi. And once all the faults are fixed, then adding equi becomes
valueless anyway in safety terms.


> The only sensible advice
> we can give in a general purpose guidance article is to say you need to
> be lead by the professional opinion of the people you have paid for
> advice

I don't see any reason for us to even comment on that.
Re equi bonding, why not just state the truth, that its required when
doing electrical work?


> and here is what the bonding does and how it works if you want to
> know. The implications of it not being there may be trivial, or may be
> very serious, we can't tell you from here.

yes we can, we know ballpark figures on this.


> (Note also this is partly a circular argument. We have very safe
> electrics in the UK as a general rule - both fixed, and appliances (the
> former more so than the latter). Deaths are very rare, and injury
> relatively rare. Part of the reason for this is that we do specify and
> install safety measures like EQ bonding, RCD protection and a host of
> other measures.

the majority of domestic installs in the UK predate equipotential
bonding, and a large percentage still have no RCD. The national death
rates from electrocution apply to all systems, risks added up, not
specifically to newer one with rcd/equi.


> > Why not...
>
> > Lets say install cost £20 materials, 4 hours labour for a diying
> > novice, including going and getting the bits.
> > Total cost £20 + 4x7-15, perhaps £40 as a balpark figure
> > = £60 total
>
> So the question that matters to me is, could that £60 save the life of
> someone in the family should something go wrong? The answer is usually yes.

The answer is fairly clear: Yes in approx 1 per 5x 20 milion
households = 1 in 100 million odds of it being of any use in each
year.


> So the next question is, how likely is it that something will go wrong
> in a dangerous way, with my particular installation, that means I would
> get to "use" that £60s worth of investment and hence make it worth
> spending here and not on mitigating some other risk. If the answer is
> "high to moderate" then you spend the £60. If the answer is "I don't
> know" the next question is can I get sufficient expert analysis at less
> cost, that would tell me if its going to make a difference. If the
> answer is no, then you spend the £60. If the answer is yes then you
> spend the money on that instead, and then possibly spend the £60
> afterwards as well depending on the outcome.

we know the answer is around one time per 20 milion households per
year. 1 per 100 million.



> > x20 million houses = £1.2 billion
>
> > If this saves one life every 5 years, thats a cost of 6 billion per
> > life saved, which is orders of magnitude higher than a whole swathe of
> > more practical constructive measures one can take.
>
> We are not talking about spending billions, since we are not writing an
> article to advice policy makers. We are talking to the individual ones
> looking at your £60 bill.

That misses the point entirely. The question that addresses is if we
have finite financial resources, as we always do, what measures are
worth taking using those resources. The calculation shows that equi
bonding is a long long way from being worthwhile. As a comparison, the
NHS has an across the board spending ceiling of £30,000 per qaly. That
is our current national level of spending on safety measures.


> >> Secondly, there is the issue of severity. I expect based on comments you
> >> have made in the past that you don't consider the lack of "required"
> >> bonding to be of particular concern. However as I see it (and as Adam
> >> highlights, as any form of proper inspection would see it), it is
> >> classed as a fairly severe fault.
>
> > That only shows a recognised flaw in such testing, namely that the
>
> Its a flaw in the process that one accepts since it controls the cost of
> such testing. A PIR plus the cost of remedial action is in many many
> cases going to be significantly less that the cost of a test with a
> detailed analysis and risk assessment to go along with it. Also doing
> the work once often saves repeating the exercise later to justify that
> something non standard is actually ok in this circumstance.

Reporting the omission more realistically as just NTCS would cost zero
more.


> > results given are sometimes entirely unrealistic and to encourage
> > needless spending.
>
> Agreed; and sometimes the results will be highly realistic, and
> encourage spending on something that needs doing as a matter of urgency.
>
> How do you differentiate without detailed technical knowledge?

national death statistics. Then one calculates approx cost/benefit for
safety measures.


> Perhaps there is a whole new article there; "My PIR said X, how much
> notice should I take?".

or 'what does this mean in real terms?'


> [1] although following the logic, part P would never have been
> introduced - which shows up the disparity between stated and real agenda.



Spending money on safety measures that yield little only leaves less
money to spend on safety measures that are of genuine importance.

In this case the cost/benefit ratio is 1/ 6billion to 1/ 30k = a ratio
of 200,000:1. IOW spending that £60 per person on useful measures
could save 200,000 as many lives as by spending it on equi bonding. So
realistically, its fatal in many cases.

Given this, why claim its always required when it isn't?

Or if you think it is required for all houses to meet latest wiring
regs, which act of law do you believe says so?


NT

On Mon, 27 Jul 2009 00:02:57 +0100, John Rumm <(E-Mail Removed)>
wrote:


>"One should also keep in mind that a room containing a bath or shower is
>classed under Part P of the building regulations as a "special
>location". This means that other than like for like changes of
>accessories etc, or the installation / upgrading of supplementary
>bonding, nearly all electrical work will be classed as a "major work"
>for the purposes of part P. Hence to comply with the requirements the
>work would need to be carried out under a building notice, or completed
>by a person who is a member of one of the various part P competent
>persons schemes. "

In England and Wales?

--
Geo