Inaccurate statement by ESC

[stillp]

From the ESC website at http://www.esc.org.uk/public/news-a...risking-lives-with-basic-electrical-blunders/
"Most electrical accidents can be prevented by a Residual Current Device (RCD), a life-saving device which prevents you from getting a fatal electric shock if you touch something live, such as a bare wire. It works by cutting power if there is a surge. However, the ESC study shows a serious lack of knowledge of this vital safety device: 70% of people surveyed do not know what an RCD is and almost half of all UK homes (49%) don’t have adequate RCD protection."

Nice to know that RCDs give us surge protection!

 

[ericmark]

There seems to be a number of errors on the ESC bulletins.
With the guidance notes on electrical condition it tells one to fail where there is a problem with extension leads.

To my mind there not fixed so not part of the remit. You could inspect a house just before handover and have builders equipment everywhere clearly you would not fail a house because of builders extension leads.

What I think we have to remember is they are GUIDANCE notes not rules. At the end of the day we are the electricians and we must use common sense.

Clearly "surge" should read "leakage" but it's not totally wrong spikes do trip my RCD and to stop it being tripped you need the more expensive types like the X-Pole or these.

Untitled

• ericmark
• 6 Dec 2008
• 34

 

[stillp]

Eric, the reason they sometimes trip on spikes is due to transient residual currents, not due to the surge per se.

By the way, you keep posting that X-pole photo - are you on commission?

 

[bernardgreen]

That does not inspire confidence in the advice that ESC hands out.

Even with an RCD cutting the power when the current un-balance reaches the trip level the shock can still be fatal. It might be that several of the deaths due to electric shock may be consequential to the shock such as a fall or an accident due to loss of lighting when the RCD removed all power.

 

[ricicle]

By the way, you keep posting that X-pole photo - are you on commission?

You read my mind !

 

[ericmark]

I don't think anyone would buy that RCD I am told about £350 each. But it does show there are different qualities and is on my picture list so easy to select.

As to the dangers I had an issue with a TV giving a shock through aerial connection and when I complained I was told only 5ma so not a danger. To which my reply was unless some one falls of the ladder as a result.

I think the whole idea of saying it's safe with a 30ma RCD is flawed. Although only for 40ms the current can still be quite high enough to kill some one not in the best of health.

Also of course it only trips when there is a path to earth. Where the path in line to neutral it will not trip.

Words like adequate do not really help. If he lives it was adequate if he dies it was not. A bit late by then. How many times do we hear yes I have a RCD then find it's a 100ma delayed type.

I was rather impressed that 30% of the general public knew what an RCD was!

However it's how you ask the question and where. If you were to walk down any canal tow path and ask if they knew what an RCD was most boat owners would say yes. However then ask what it was and they would tell you its the Recreational Craft Directive.

I am amazed that 51% of homes have adequate RCD protection. I would have expected a much lower figure. I would guess in my street less than 10% would have RCD protection complying with BS7671:2008.

So hands up who has lights in bathroom with RCD protection? Not really a fair question on a electric forum but lets see. For me the answer is yes I do have RCD 30ma at 40ms on all items.

 

[stillp]

Eric, remember that 96.325% of statistics are made up to prove a point!

Perhaps you should find some more pictures of intelligent RCDs!

The protection offered is even worse than you think, the thresholds for RCD operation are based on the tolerance to a shock of the 95th percentile of the population, i.e. 5% of people will die anyway.

I share your surprise at the percentage of people who claimed to know what an RCD was and also at the figure for the percentage of homes apparently having RCD protection. Did they, I wonder, check if the respondents actually knew what an RCD was? I suspect the question was something like "does your house have something to protect you from an electric shock", to which most people would reply in the positive, while thinking of the fuseboard, even if an old rewireable type.

 

[JohnW2]

I think the whole idea of saying it's safe with a 30ma RCD is flawed. Although only for 40ms the current can still be quite high enough to kill some one not in the best of health.

True - but, worse, a 30 mA RCD doesn't necessarily protect a fully healthy individual from death when a current is flowing through them to 'earth' (and, as you say, offers no protection at all against a current flowing from L to N through a human body). Don't forget that, despite the oft-discussed 'common misconception', a 30mA RCD does not limit the current at all (to 30mA or any other figure), it merely limits the duration of any current of at least 30 mA magnitude. With very wet skin, one can easily get currents 10 times that through a human body - and 300 mA for 40 ms would be enough to kill a good proportion of fully healthy individuals exposed to it.

Kind Regards, John

 

[plugwash]

To my mind there not fixed so not part of the remit. You could inspect a house just before handover and have builders equipment everywhere clearly you would not fail a house because of builders extension leads.

OTOH I think there is a need to take a more holistic approach to electrical safety. IMO whether an electrical installation is fit for purpose can only be judged in light of it's intended and actual use. If people are running extension leads across doorways, roads or whatever on a regular basis and/or leaving long extension leads semi-permanently installed then it probablly* indicates a deficiency in the fixed installation.

Builders are IMO a different case because they are clearly temporary, not part of the isntallations regular use.

* I'm sure there are situations where fixed wiring close to the point of use is impractical and so long extension leads are inevitable. However in such cases there should be a clear H&S policy on precautions surrounding those extension leads.

 

[17thman]

a more holistic approach

can one be "more holistic"?

 

[JohnW2]

a more holistic approach ... can one be "more holistic"?

Probably not, but I guess that "holistic" is 'more' than "semi-holistic" or "non-holistic"

Kind Regards, John