Is metal stud-work required to be earthed?

[SimonH2]

We could discuss whether the studwork should be earthed - and specifically whether that creates more hazards than it removes.
But one obvious mitigation is to require all circuits to have RCD protection - that should have tripped the supply in that case, causing an apparent nuisance trip, and probably getting the cause found without it being fatal. Perhaps we should suggest that as a new reg

 

[Iggifer]

It is on the NICEIC EICR (and I assume others), can't say I've come across any metal stud work that wasn't in new builds at all (which are obviously all RCD protected and thus irrelevant)

 

[JohnW2]

We could discuss whether the studwork should be earthed - and specifically whether that creates more hazards than it removes. But one obvious mitigation is to require all circuits to have RCD protection - that should have tripped the supply in that case, causing an apparent nuisance trip, and probably getting the cause found without it being fatal.

Do you think so? If my recollection of the case is correct, there probably wouldn't have been any significant leakage current until the unfortunate victim provided a path from the puddle of water to earth - unless the puddle was in contact with something else earthed..

I agree that an RCD might have prevented that current through her flowing for long enough for it to be fatal but, if my recollection of the circumstances is correct, an RCD might well not have operated prior to that event.

Kind Regards, John

 

[SimonH2]

If my recollection of the case is correct, there probably wouldn't have been any significant leakage current until the unfortunate victim provided a path from the puddle of water to earth - unless the puddle was in contact with something else earthed.

Indeed

I agree that an RCD might have prevented that current through her flowing for long enough for it to be fatal but, if my recollection of the circumstances is correct, an RCD might well not have operated prior to that event.

I agree, it may well have not operated before the lady knelt down in the puddle - but the whole point of these RCDs is to trip in a short enough time to avoid death to the human in the circuit (most of the time, nothing is certain).

 

[JohnW2]

I agree, it may well have not operated before the lady knelt down in the puddle - but the whole point of these RCDs is to trip in a short enough time to avoid death to the human in the circuit (most of the time, nothing is certain).

Indeed. It might have saved her life, although that is far from certain. However, I don't think it would/could have been regarded as a 'nuisance trip', as you suggested, since the person who experienced a shock severe enough to trip an RCD would (if still alive) be likely to know otherwise!

I am still waiting to hear of a definite story/report about a person who has experienced an electric shock which caused and RCD to trip, and survived. Such a person, if one can be found, might have died in the absence of the RCD - although, of course, we would never know for sure what would have happened.

Kind Regards, John

 

[John D v2.0]

I am still waiting to hear of a definite story/report about a person who has experienced an electric shock which caused and RCD to trip, and survived

Oh yes, seems like I'm still alive, grabbed a live terminal behind a cooker switch by mistake.

 

[JohnW2]

Oh yes, seems like I'm still alive, grabbed a live terminal behind a cooker switch by mistake.

I hate this medium sometimes, particularly when emoticons have not been used to to improve this a bit!! Accordingly, silly/embarrassing though it may be to have to do so (rather than guess) I suppose have to ask .....

.... Is that intended as a humorous comment, or as a serious statement of something that happened and caused an RCD to trip?!!

Kind Regards, John

 

[davelx]

I am still waiting to hear of a definite story/report about a person who has experienced an electric shock which caused and RCD to trip, and survived. Such a person, if one can be found, might have died in the absence of the RCD - although, of course, we would never know for sure what would have happened.

Kind Regards, John

I have - although it was only the back of my hand bridging the terminals on a transformer.

 

[John D v2.0]

I hate this medium sometimes, particularly when emoticons have not been used to to improve this a bit!! Accordingly, silly/embarrassing though it may be to have to do so (rather than guess) I suppose have to ask .....

.... Is that intended as a humorous comment, or as a serious statement of something that happened and caused an RCD to trip?!!

Kind Regards, John

Yes it actually happened, but given the RCD should have tripped in 30ms I'm ok but a bit shocked.
There's a YouTube video where some guy rigged up a system to give himself electric shocks that he could adjust, I think he got up to about 20ma before he had to stop. That might trip an RCD even.
I think my shock was likely only across one hand, so I don't see why I should have suffered any damage.

 

[ban-all-sheds]

House was wired to 16th Ed. in 2002 and has RCD protected sockets, but the lighting circuits are not

The 17th requires all the cables to be RCD protected.

 

[ban-all-sheds]

Hmm, wasn't there a case a while ago where the studding became live due to a board fixing screw having gone through a cable - and it only came to light when some water pooled on the floor ?
Ah yes, here it was - one of those "chain of issues" which all had to happen to cause the fatality.
Short version: metal studwork, a board fixing screw went through a cable and made the studwork live, that persisted for some time undetected and without causing any problem, the boiler then leaked and formed a pool of water which contacted the studwork, the occupier knelt down to mop up the water and (I assume) then made a circuit between the live water and some earthed metalwork on the boiler, the electric shock was fatal.

So did the RCD not protect them? I know there's no guarantee that they will - was that one of the cases?

 

[SimonH2]

There's a YouTube video where some guy rigged up a system to give himself electric shocks that he could adjust, I think he got up to about 20ma before he had to stop. That might trip an RCD even.

Don't forget that an RCD doesn't limit the current, only the duration. So potentially many amps could flow through a person's body until the RCD trips.

So did the RCD not protect them? I know there's no guarantee that they will - was that one of the cases?

I'm assuming there was no RCD (on the circuit), it happened in 2007 and there isn't much information to say when the apartments were done. Unless someone can find a more detailed report, we won't know either way.

 

[John D v2.0]

Don't forget that an RCD doesn't limit the current, only the duration. So potentially many amps could flow through a person's body until the RCD trips.

Indeed. Although John w question was whether it had ever tripped and the person hasn't died, so I would assume someone had an only 30ma shock at some point due to not directly touching earthed metal, even if most mains shocks would be more than that or less

 

[JohnW2]

Yes it actually happened, but given the RCD should have tripped in 30ms I'm ok but a bit shocked. .... I think my shock was likely only across one hand, so I don't see why I should have suffered any damage.

Interesting. OK, that's two of you (dave1x and yourself), then. However, it sounds as if, in both cases, the shock current path was probably restricted to just one hand - so unless there were some other path from yourselves to earth, it's extremely unlikely that the shocks would have been fatal, even in the absence of an RCD.

Although it's obviously impossible to be certain, I therefore would not personally count either of those as cases in which it was at all likely that an RCD had "saved a life".

Kind Regards, John

 

[John D v2.0]

I am still waiting to hear of a definite story/report about a person who has experienced an electric shock which caused and RCD to trip, and survived. Such a person, if one can be found, might have died in the absence of the RCD - although, of course, we would never know for sure what would have happened.

Although it's obviously impossible to be certain, I therefore would not personally count either of those as cases in which it was at all likely that an RCD had "saved a life".

Well as per your first post, I certainly might have died, I'm certainly glad there was an RCD. Given my lake of experience of electric shocks there's a good possibility my other hand was touching earthed metal on the back of the cooker switch rather than the other one. I'm not sure what would have had to have happened to fulfill your criteria, lying in a metal earthed bath with live wires connected into my heart?
I'm happy there's a significant window of opportunity for an RCD to save a life by tripping due to an electric shock. But I have no direct evidence for obvious reasons.