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.
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).
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.
You removed the statement that it was required if doing electrical work, replacing it with the erroneous claim that its required in all cases.
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.
Telling the truth about the legal position is not reckless or unwise.
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.
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 =A360 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 =A360 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?
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.
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?
yes we can, we know ballpark figures on this.
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.
The answer is fairly clear: Yes in approx 1 per 5x 20 milion households =3D 1 in 100 million odds of it being of any use in each year.
we know the answer is around one time per 20 milion households per year. 1 per 100 million.
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 =A330,000 per qaly. That is our current national level of spending on safety measures.
Reporting the omission more realistically as just NTCS would cost zero more.
national death statistics. Then one calculates approx cost/benefit for safety measures.
or 'what does this mean in real terms?'
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 =3D a ratio of 200,000:1. IOW spending that =A360 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?
We can go round in circles on this. Yes I agree there is no legal requirement to bring an old install up to current standards. Unless you change anything. However that just means that it is allowed to to be non compliant with the technical spec. The spec's requirement's however have not changed.
Your cost benefit analysis is looking at it from the wrong perspective. I agree that there would be no point in legislating that all properties must be inspected and have it added if required and missing. The cost would be disproportionate to the benefit.
However that is a very different argument from the case where you have been informed by a professional that the installation is at fault and you need to asses the significance of that fault.
If you are doing nothing to an installation, then you are not obliged to upgrade it to meet the requirements.
We are not talking about the legal requirements. We are talking about giving good advice, and doing a proper job. We have already stated the legal position. By all means add further words if you think it would help.
Again you are attempting to carry out an epidemiological study (without access to the raw data I might add). We are dealing with rare events and small sample sets. We may hear about the deaths, we probably don't hear about the vast majority of injuries and shocks.
It remains the case that EQ bonding in a bathroom is a cheap and easy fail safe measure that may well be conclusive in the event of another failure.
You don't provide enough information to make the choice. If your particular bathroom happened to be like the one that Andy W posted a link about, then the liklihood that you are going to fall into your 0.2% is very nearly 100%. Its a pretty good certainly that someone would get a serious shock before long.
If money is so tight, then why pay the £200 - £400 for a PIR if you are not going to be in a position to fix any faults it finds? You would be better of fixing the car and spending some time reading about what constitutes a safe electrical system.
I don't agree. EQ bonding is a fail safe technology. Fixing current faults is no protection against those that may occur in the future. Bonding is.
We have said you are not legally obliged to upgrade. That is closer to the truth I would say.
Most informed people asked to say where the *requirements* for electrical installations are specified, would say BS7671. According to that, bonding is required (17th edtn spec installs excepted).
Without detailed knowledge of the installation in question you don't, you only have stats which by definition are not specific.
Do you have a source for this claim? EQ bonding goes back to at least the 14th edition - so that is 1966. I would be very surprised is pre WWII wiring installs were still in the majority.
useless analysis - we are not talking generalisations. I want to know what it means for *my* installation.
we don;t actually - even in general terms. There could be hundreds of people who are alive, well and uninjured or hurt that are possibly even unaware that they were saved by a protective system such as those being discussed.
No, I can't see the logic here.
Depending on the *actual circumstances* the chance that a protective measure will have a decisive effect on the outcome will vary in probability from nil to 100%. Personally, if the risk in my house is nearing 100% I am not going to draw any comfort from the fact that according to national statistics I died in a very improbable way.
yup. However to do any good, it is going to have to impart sufficient technical know how to make a decision based on the facts of the actual installation, and not just state heuristics based on statistical likelihoods.
woosh...
How about because the requirements say so?
I believe one is not legally obliged to upgrade to meet the current requirements. If you want the requirements they are available from Amazon et al.
ok, to save going round this loop any more, I have added the following words to the earthing and bonding article:
On the subject of main bonding:
"Note that if the main bonding is not present, it is considered to be a serious electrical fault. As a result anyone carrying out modifications to any part of an electrical installation should also check and rectify any faults in this area at the same time. Note that although there is no general legal obligation on house owners to upgrade the electrical system to meet the current requirements as laid down in BS7671 (the "wiring regs"), it is not uncommon for professional electricians to refuse to undertake any other work unless their are also instructed to perform any required remedial work on the main bonding at the same time."
and on the supplementary bonding bit:
"Again a householder is not legally obliged to upgrade or install supplementary bonding when it is required (by the wiring regs) but missing, (or in some other way substandard), unless they are carrying out other work in the same room. "
I have also added a note to the bathroom article to the effect:
"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. "
I suggest that should say "notifiable work" to avoid any confusion with the major/minor distinction between work done on a 'normal' EIC, as opposed to a minor works certificate (a separate, albeit related, issue).
No Part P in NI, AIUI, unless things have changed.
the bathroom article shows an incorrectly fitted BS 951 earth clamp. The embossed aluminium label should be fixed through one of the round holes, under the lock nut on the clamping screw.
They are usually under the locknut and cause no trouble. Having said that the requirement is merely that they are visible and not [easily] removed. Complaining about *how* they are attached is ridiculous.
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