elctric shock

[momin]

hi everybody. I'm new, so please excuse me if i do any thing wrong. My daughter had electric shock in the shower. I switched off the consumer unit., but it was still alive. so we had to pull her off the chrome hose which she was grabbing. we had a shared loop from our next door neighbour. He had some work done a few times previously a year ago. There was no marking on his workers van. we called the ambulance and she was taken to hospital. the electricity board was also called. they took out the main 60 amps fuse, but the radiators and pipes were still alive. he called in more senior electrician from the board. they too had never ever come across such a situation. the managers were called in as well. my loop was coming from next door. they went in. as soon as they put their meter to test, there was a big bang and a flash. when asked, what happened, the electricians said that my earth cable was hanging loose. the board , on our insistence, wrote to the neighbour to assist them in their investigations and to name the person who carried out his work. He has not responded. it is 6 months now. the board says they do NOT have any remit or power to force him. So what do i do now. Please, please advise asap.

 

[Yooj]

I would say that the supply would be a PME still, and you just note the spike on the cert...All the spike is doing is acting like the metallic utilities pipework, but providing a further return path in the eventuality of a neutral supply O/C.

I don't think that an RCD would be required in this case.

Yooj

 

[Des 56]

Yooj, 41+ years Sparky- and every day I find something I didn't know!
Supplement a PME with a spike;

How would you show the earthing arrangement on paper. TNC/S- TT- or both?

Would you need to put a 100ma main switch at the front to make the TT system valid if used?

As Yooj stated,the system earth would still be TNC-S The earth spike being a suuplementary earth for the line spiked neutral,this has been a recomendation of the IET for these installations for improved safety

It may have prevented the daughter from having the shock whatever the system fault turned out to be

 

[Yooj]

Hi Des56, all the posts I read of yours leads me to think that you provide a good voice of reason....in light of this, what do you make of the situation that has occured in this installation, as for me, something just does not appear to add up, and I cannot put my finger on it.

Yooj

 

[Des 56]

It would be difficult for anyone to give a remote assessment of what went on,we can all only use the little information and try to fill in the blanks
For me i suspect a lot of covering your ar--e as gone on and if anything something extra nauhty as gone on,it would be nigh on impossible to show any negligence

I think,disconnected main earth,shared pipework becomes live through fault,no earth connection of these pipes other than through the water because of no effective bonding next door,perhaps no rcd ,the fault from next door remains until discharged through the daughter touching the charged pipes and something earthy
If it was a fault or ineffective bonding in his own house,his RCd would have seen it bonding or no bonding,as it was next doors fault,no imbalance and relying on next doors protection,which may not have existed
The dis connected main earth being the big tomatoe issue

Forgot this
I cant see the loss of a supply neutral causing the problem,because the systems were still in use via earth or neutral whichever,so,
Fuse removed from his house,pipes still live,earth reconnected next door, big flash as the live earth fault has now got a different route

Did I hear you say

What a load of bulll,sorry guesswork

 

[Yooj]

Yep, just a load of hypothesis

I don't think we will ever know what happened for sure...though I firmly beleive that it was a catalogue of events rather than a single thing which caused it...

Plenty seems to have been swept under the carpet though.

Shame we will not know for sure, as this would have been a really good case-study to get my teeth into.

Yooj

 

[d1scv]

Didn't like to say anything till now- BUT one bit of the puzzle is missing.
I agree that I cannot put my finger on it.

 

[mechelec]

As Yooj stated,the system earth would still be TNC-S The earth spike being a suuplementary earth for the line spiked neutral,this has been a recomendation of the IET for these installations for improved safety

It may have prevented the daughter from having the shock whatever the system fault turned out to be

be carefull using an earth rod in conjunction with PME as a fault on the network resulting in a lost neutral near your property may result in all your bonded metalwork becoming live!!!!!!!!!!!!!

My blood also boils when people do not read and properly understand the message. I did not play with the electricity. the fault was in the loop from next door. he had electricians working there, not me. also the electricity board did a very very thorough check of my house. every thing was ok.

(I am presuming the existing earthing arrangment was TNS with paper lead cable, lead sheath used for earth)
Im sorry to say that everything was not ok with your house before the accident as if a Ze test was carried out then it would have shown a high reading. I appreciate that through no fault of your own a fault has occured.
As a note if anyone has a looped service like this ie paper lead cable lead sheath used for earth, to avoid what is a common problem (ie earth becoming disconnected) apply for a PME this way the neutral is used for the combined purposes of N and E and you are not relying on a connection in someone elses property.

 

[momin]

Sorry to hear about your daughter's bad experience momin.

I've got one point:

whether this was a broken neutral/earth in a pme context, or a shared/looped earth between neighbouring dwellings, or both .... it's the DNO's responsibilty to provide an (external) earth path for every installation. If that path was broken due to a broken neutral then the liability is theirs; similarly, if an installation is without an earth path because it it shared with an adjacent installation and disconnected there (for maintenance or modification of that installation), it's still the DNO's responsibility.

Maybe a solicitor would be more appropriate than an electrician in this context.

Thanks mate. I will write to the electricity board, as u have advised. By the way what does DNO stand for. I wish u and everybody else a year happy christmas and a happy new year. And many thanks for the good advice given in the recent days, by everyone of you guys.

 

[Heating bloke]

be carefull using an earth rod in conjunction with PME as a fault on the network resulting in a lost neutral near your property may result in all your bonded metalwork becoming live!!!!!!!!!!!!!

Wow, this thread has been a real eye-opener for me. It sounds like something you hear happen in Spanish hotel! But (not being a sparky) I don't understand the above quote, can you please explain why the bonded metalwork would become live, or do you mean 'if there was a live-to-earth fault the metalwork would become live as there qould be no neutral or earth'?

We get some great(!) faults in heating and water, and even sometimes people haven't vented their hot water tank, or put a non-return valve on a hot supply (so no expansion can be taken up), but we don't get truly horrifying stories like this! The closest I've seen to disaster was a customer of mine who asked me to service his gas fire. Being diligent I carried out a smoke test on his flue - only to discover that the cavity wall insulators (a week earlier) had filled it up with foam! Luckily for him, it was still summer and he hadn't used the fire yet! It was weird to think that I probably saved his life that day - and all his family.

I had always thought that having your own electrics checked and passed as fine makes you secure. I didn't realise that your neighbour's electrics could affect yours! Wow!

 

[Des 56]

be carefull using an earth rod in conjunction with PME as a fault on the network resulting in a lost neutral near your property may result in all your bonded metalwork becoming live!!!!!!!!!!!!!

Just to trying to swing the opinions of members of the forum
I found this advise from the IET

Earth rods and PME supplies
Guidance by the IEE can be read here


Wiring Matters magazine - pre-2004 - The IET

Click PME supplies and esc regulations
Open the file
Then go to paragraph 4

It includes this

The Commentary on the IEE Wiring Regulations includes much more detailed and
practical advice including advice prepared at the request of the DTI on further
precautions that can be taken to reduce the risk associated with PME supplies. The
UK National Committee considered this matter and recommend an earth electrode is
connected to the main PME earthing terminal. This is a very practical solution. The
Commentary on BS 7671 amongst its comprehensive advice provides specific
guidance as to how the maximum earth electrode resistance can be calculated for
particular installations e.g. house, swimming pool, farm etc. This approach provides
the reliability and security of a PME supply whilst protecting against the loss of PEN
continuity (however unlikely an event this mat be).

 

[d1scv]

be carefull using an earth rod in conjunction with PME as a fault on the network resulting in a lost neutral near your property may result in all your bonded metalwork becoming live!!!!!!!!!!!!!


An earth spike [question] would only serve to reduce the possible effect of a lost neutral ?

One more thought, in all my years I got 2 belts, both from borrowed neutrals.
230AC. Both threw me BIG time- certainly did not grab me.

 

[Heating bloke]

I thought only DC grabbed you, and AC threw you off.

d1scv. I've had about seven or eight electric shocks. Funnily enough I've gone about 20 years without getting one, then had two in two weeks earlier this year.

 

[Des 56]

I thought only DC grabbed you, and AC threw you off.

.

I am going to be argumentative for the hell of it


I say 400 + volts AC will grab you






Care to prove me wrong with a pratical demonstration?

 

[Heating bloke]

Okay, fair enough, but why would the guy's daughter have got 400 volts?

 

[Notsosmart]

I am going to be argumentative for the hell of it

I say 400 + volts AC will grab you

Care to prove me wrong with a pratical demonstration?

Current doesn't 'grab' you Its the muscles involuntarily clenching

Practical demonstration you say?: as an apprentice 30 years ago I had the misfortune to put my palm across 2 phases of a live 415v o/l relay with open contacts: not to be recomended I was unable to move until I concentrated hard on dragging my arm away whilst roaring a shout.
The spark working on the panel (who hadn't warned me it was still live) just looked up & said "By the way be careful whilst you are labelling the contactors"!!

 

[d1scv]

I now think we are all wrong!
Done a bit of research. Put simply, it would seem that all electic shock cause you to grab- AC & DC.

I think the apparent contradictory results- stuck or thrown- are dependent on other factors.

Our victim above, that received 415 straight across his hand, grabbed and got stuck.

In my case, 230 through my fingers and thence down the body, I guess my hand grabbed causing my fingers to clear the live wire, my legs also grabbed. Throwing me across the room.


My theory based on Physiological effects of electricity : ELECTRICAL SAFETY

 

[Deleted member 9648]

Sorry but I dont see how an electric shock can "throw you across the room"....I've had a few minor belts in my time but I've not been "Thrown across the room".....and yet everyone else who gets a handful claims they were "Thrown across the room".

 

[d1scv]

Sorry but I dont see how an electric shock can "throw you across the room"....I've had a few minor belts in my time but I've not been "Thrown across the room".....and yet everyone else who gets a handful claims they were "Thrown across the room".

Trust me- I finished up in a heap a good 12 ft away.

And it was all in ultra slow motion- I can remember whilst travelling trying to work out how on earth that had happened.

But I think your comment might help to validated my theory. In my case I was sitting on a stool and the belt caused my legs to kick. Perhaps you were standing- thus the sudden kick would not have the same effect.

I'll try and dig out the case of the shock victim that survived- but took his mate out on the way.

 

[Heating bloke]

Well, as I said, I've had seven - and one not-so-bad through a faulty neon screwdriver while standing on an aluminium ladder. Each time it just made my hand fly off in shock/surprise. About the third one I had was placing all my fingers on a busbar as I gripped it to disconnect a screw. I remember pretty much throwing the thing and swearing. The customer asked me if there was anything wrong, and I apologised. I don't intend to have any more as I really hate it! That rapid throbbing (which I suppose is the hertz) can upset your day.

 

[kung]

the real questions that I would be asking, would be to the DNO in terms of why was the Main Earth to Momin's terminated in the neighbours house,
Yooj

Could be a loop in & loop out system ! The DNO have done this on a few areas to save money, i have the same system in my house.