Earthing a water pipe??

[bernardgreen]

The death of Emma Shaw

http://www.cps.gov.uk/westmidlands/...ty_in_connection_with_the_death_of_emma_shaw/

could have been prevented if the metal studwork frame of the walls had been connected to the MET. Had the metal stud work been connected to the MET then when the screw shorted the Live to the metal stud work a protective device would have operated and shown there was a fault as well as disconnecting the power..

As I understand it at the time the frame work did not need to be earthed or bonded to the MET as it was not considered necessary since none of the metal frame was exposed and could not be touched..

If the metal frame was covered by plaster board then how would one test that it was not Live ?

 

[Jadele]

How would anyone know it was metal.

 

[John D v2.0]

Those electricians needed a better solicitor. There's no way a Eicr should have detected that fault. They might have happened to notice it, but I can't think which test should have revealed it.

From the link: ""The purpose of electrical testing and inspection is to detect any hazards. By signing off the testing records, Neil Hoult certified that the electrical installations in Emma Shaw's new build flat were problem free and safe. "
Wrong, the inspection is to report that it complies with bs7671 as far as can be ascertained through the prescribed testing procedures.

This guy would have been saved if he earthed his wedding ring. http://www.dailymail.co.uk/news/art...ouching-copper-wire-wearing-wedding-ring.html I'm going to add a connection from mine to the main earthing terminal now

 

[Jadele]

There must be more to it and they must have been the installers so it would be an installation cert. It would be very harsh for a PIR as you say

 

[John D v2.0]

There must be more to it and they must have been the installers so it would be an installation cert. It would be very harsh for a PIR as you say

Agreed, the report is very light on detail. But even for installation, even if you first fix correctly, by the time you second fix someone could have easily damaged a cable in a way you can't detect. By the time you sign the certificate, anything could cause a danger, but you're not signing to say it's safe anyway.

 

[Jadele]

So are we to assume that the stop valve was the only metal part touching the metal in the wall and that the rest was plastic piping? If that's how it's happened these sparkies were incredibly unlucky

 

[JohnW2]

So now its really about earthing that piece of pipework in the kitchen or not and there are various schools of thought on that within this thread

Indeed, and those differing schools of thought exist because it is a 'swings and roundabouts' situation, and different people will have different opinions about which of two possible scenarios is the more likely.

Pipes, per se, are not much of an issue, since they are rarely touched directly (and are often not very accessible to be touched). There is much more to talk about when the metal pipe connects to easily-touchable metal, such as a metal kitchen sink. There are then two possible scenarios to consider, both arising if an electrical appliance (kettle, toaster, blender etc.) becomes faulty, or a cable becomes damaged, such that touchable parts of it become 'live' ....

1... that live part comes into contact with the metal sink (or whatever). A person then touches that sink at the same time as touching something else which is at earth potential.

2... a person comes into contact with the live part at the same time as touching the sink (but nothing else).

In case (1), if the sink is not earthed, the sink will remain live, so that a person touch it and something earthed will suffer a shock. If the sink is earthed, then a protective device (RCD, MCB or fuse) should operate as soon as the faulty object comes in contact with the sink, so that the sink no longer represents a hazard to someone touching it.

In case (2), if the sink is not earthed, a person touching it at the same time as touching a life faulty appliance should not get a shock - since, although they are in contact with 'live' electricity, there is no path through them to earth. If the sink is earthed, they will receive a shock, since current flows through them from the faulty device to the earthed sink.

In both cases, if the circuit supplying the faulty appliance/cable is RCD protected, the RCD should limit the duration of any electric shock.

So, if one believes that (1) is more likely than (2), then earthing the sink is the better bet, although it increases the chance of an electric shock in scenario (2). If one believes that (2) is more likely than (1), then not earthing the sink is the better bet, although it increases the chance of an electric shock in scenario (1).

It is differences in views as to which is the more likely scenario which leads to different opinions as to whether or not one should earth a kitchen sink (by earthing metal pipe connected to it), if the pipe in question does not require bonding and which, in the absence of explicit 'earthing' would be 'floating' (not connected to earth.

However, in practice, that last comment makes this discussion almost moot. Metal water pipes are almost always unavoidably earthed, via the CPCs of boilers, immersion heaters, CH pumps/valves etc. etc. and connections between pipes - so the question of whether or not one should ('additionally') explicitly earth the pipe with a bit of wire becomes irrelevant.

Kind Regards, John

 

[John D v2.0]

So that comprehensive description together with Bernard's link raises the question that is all conductive building material inherently creating an additional unnecessary danger?

Should we be avoiding installing any conductive building materials at all?

Perhaps plastic pipework, timber studwork, composite sink (class II house in a way) would be the best way? An earth free environment is always going to be safest after all.
Or my new suit

 

[Jadele]

I hate that metal studwork sadly it appears its here to stay

 

[JohnW2]

The death of Emma Shaw ... could have been prevented if the metal studwork frame of the walls had been connected to the MET. Had the metal stud work been connected to the MET then when the screw shorted the Live to the metal stud work a protective device would have operated and shown there was a fault as well as disconnecting the power..

That is true. However, as I've just written, if the stud work had been earthed then, in a different situation, had she somehow been in contact with that at the same time as touching, say, an exposed live core of a damaged vacuum cleaner cable, she would have received a shock which she probably would not have received if the stud work had not been earthed.

So, as I just wrote, the decision whether or not to earth otherwise 'floating' metal depends on a judgement as to which of various possible scenarios are the more likely. It can be a very difficult judgement since, taking this example, what happened to Emma Shaw and the hypothesised situation with a damaged appliance lead I mentioned are both incredibly unlikley scenarios.

Kind Regards, John

 

[JohnW2]

So that comprehensive description together with Bernard's link raises the question that is all conductive building material inherently creating an additional unnecessary danger? Should we be avoiding installing any conductive building materials at all? Perhaps plastic pipework, timber studwork, composite sink (class II house in a way) would be the best way? An earth free environment is always going to be safest after all.

Indeed - as we know, a totally earth-free environment is the safest, and if that were attainable, it wouldn't really matter whether building materials were conductive or not - since the only risk of electric shock which could then arise in relation to building materials would be due to two simultaneously touchable conductive parts coming into contact with Line and Neutral conductors respectively - a risk so small that it could probably be ignored!

Kind Regards, John

 

[bernardgreen]

if the stud work had been earthed then, in a different situation, had she somehow been in contact with that at the same time as touching, say,

As I recall it the stud work was completely encased in plaster board and then a skim coat covering the heads of the plaster screws. Hence for a person to make contact with the metal stud work would require some of the plaster board to be removed.

 

[John D v2.0]

Indeed - as we know, a totally earth-free environment is the safest, and if that were attainable, it wouldn't really matter whether building materials were conductive or not - since the only risk of electric shock which could then arise in relation to building materials would be due to two simultaneously touchable conductive parts coming into contact with Line and Neutral conductors respectively - a risk so small that it could probably be ignored!

Kind Regards, John

Well, one of those faults could exist for years without you knowing! The risk of you personally coming into contact with both in a metal free environment would be even lowerbut yes, this is more of a thought experiment.

 

[EFLImpudence]

There is also the case of the MP's daughter in which case it would have been better if the washing machine had NOT been earthed.

Is anyone going to promote NOT earthing appliances as a desirable idea?

 

[JohnW2]

As I recall it the stud work was completely encased in plaster board and then a skim coat covering the heads of the plaster screws. Hence for a person to make contact with the metal stud work would require some of the plaster board to be removed.

Without doing some reading to refresh my mind, I can't remember the details, but if the 'live' stud work (even if, itself, inaccessible) was in continuity with something which, when touched , resulted in a fatal electric shock, then had that stud work been earthed, then contact with that same 'something' at the same time as contact with a 'live' damaged appliance cable would presumably have resulted in a shock that would not have occurred had the stud work not been earthed, wouldn't it.

Although it gets a lot of attention, this particular tragedy seems to have resulted from one of those situations of 'vanishingly small' probability (with apologies to EFLI!). - probably no more likely to be repeated than the (very improbable) scenario with a damaged appliance lead I have been mentioning.

Kind Regards, John