Removal of supplementary bonding in bathroom?

[ebee]

Do you feel happy with the reliance on a device with a possible approx 7% failure rate that , if working correctly, would be expected to save 95% of the population (meaning it would not save 5%) or would you rather that supp bonding is giving someone another chance?

 

[JohnnyG]

Do you feel happy with the reliance on a device with a possible approx 7% failure rate that , if working correctly, would be expected to save 95% of the population (meaning it would not save 5%) or would you rather that supp bonding is giving someone another chance?

Do you still install supplementary bonding irrespective of whether it's 'required' or not?

 

[dingbat]

Do you feel happy with the reliance on a device with a possible approx 7% failure rate that , if working correctly, would be expected to save 95% of the population (meaning it would not save 5%) or would you rather that supp bonding is giving someone another chance?

Ebee. If you understand the subject then you'll realise that I am not advocating removing the supplementary bonding. Rather, I am suggesting the supplementary conductors may not be necessary to achieve the objective. In fact the existence of supplementary conductors, in most cases I have seen, introduce hazards that were not there without them; I refer to the widespread and incorrect practice of bonding together all extraneous conductive parts, but ignoring the essential inclusion of exposed conductive parts.

 

[DetlefSchmitz]

Do you feel happy with the reliance on a device with a possible approx 7% failure rate that , if working correctly, would be expected to save 95% of the population (meaning it would not save 5%) or would you rather that supp bonding is giving someone another chance?

Quote the source of your data, and once again we can go through the fact that it is not actually based in a true interpretation of the original article.

 

[EFLImpudence]

Hi all,

Can I add what I think may be a useful point?

A lot of people seem to be under the impression that there are ONLY exposed conductive parts and extraneous conductive parts - not realising that ONLY when a part needs to be supplementary bonded is it then considered to BE an extraneous conductive part.

There can be metal parts and indeed pipes that are not extraneous conductive parts.

Hope this helps.

 

[ebee]

www.era.co.uk/news/pr0709.asp


RCD failure to protect 5% of the population is taken from the wirtings of Biegelmeier and lee

 

[dingbat]

A lot of people seem to be under the impression that there are ONLY exposed conductive parts and extraneous conductive parts - not realising that ONLY when a part needs to be supplementary bonded is it then considered to BE an extraneous conductive part.

Your explanation is the wrong way round. However, this bit:

There can be metal parts and indeed pipes that are not extraneous conductive parts.

is correct.

Go back to your definitions in BS 7671 and all becomes clear.

 

[EFLImpudence]

Yes, thanks.

I should have said:

Only when the measurements (RA x IΔn ≤ 50V) dictate is a conductive part considered to BE extraneous and so shall be bonded.

Regards.

 

[riveralt]

www.era.co.uk/news/pr0709.asp
RCD failure to protect 5% of the population is taken from the wirtings of Biegelmeier and lee

Lies, damn lies and then there are statistics.

This piece of research focused on the possibility of mechanical breakdown of RCDs. The first phase has just looked a previous data in Italy from 2007, not the UK. The second phase will look at the domestic UK.
Your statement that they fail to protect 5% of the population is totally misleading. There are approximately 26 millions homes in the UK. So you are saying that RCD's will fail to protect 1.3 million homes - rubbish.

How does that square with the ESC statement that nearly 13 million homes do not have RCD protection in the first place.

As an aside the fact that the author of this website refers to RCD's as supplementary protection rather than Additional Protection is rather worrying.

 

[ebee]

Biegelmeier and lee did suggets that a 95% might be a good figure to work on , it's not foolproof as they were not allowed to do practical tests on real people and count the daed but their theories are the best we have to go on.

Apparently the Nazis had no such scruples and did some tests during the war giving results for 15mA and less being fatal if the right (or wrong!) conditions were met.

The 7% italian tests although do tally (very roughly) with some data gained from others.


Remember I did say about/approx.

From experience by myself and others RCDs fail by either failing to work completely or by being outside their trip times - "Stiction" being perhaps a major factor.

Once connected to a working circuit trip times do alter either by being longer or shorter.

It is rare to find an RCD uncoonnected whose trip time is less than half the rating.

So the 5% & 7% rates might be a good as an"approximation" as any.

 

[JohnnyG]

That article was also published 3.5 years ago.
Would be nice to see if that claimed % is still the same now.

 

[riveralt]

Biegelmeier and lee did suggets that a 95% might be a good figure to work on , it's not foolproof as they were not allowed to do practical tests on real people and count the daed but their theories are the best we have to go on.

Stop digging!

Apparently the Nazis had no such scruples and did some tests during the war giving results for 15mA and less being fatal if the right (or wrong!) conditions were met.

Really stop digging.

The 7% italian tests although do tally (very roughly) with some data gained from others.

Must be a really big hole by now.

Remember I did say about/approx.

You mean your not sure.

So the 5% & 7% rates might be a good as an"approximation" as any.

Ah so you are sure - not

 

[dingbat]

I should have said:

Only when the measurements (RA x IΔn ≤ 50V) dictate is a conductive part considered to BE extraneous and so shall be bonded.

No. That's wrong as well.

Regardless of the calculation to decide whether or not supplementary bonding conductors need to be employed, an extraneous conductive part is an extraneous conductive part, is an extraneous conductive part. As I said, refer to the definition (p.24)

 

[ebee]

I am not digging 5% is the best answer we got.
In the same way 7% might be a good answer .


Most answers in life are an approximation
"what time is if?" how many would say it's "33 and three quarters seconds past one seventeevn PM!" ?

Not many but quarter past one or between quarter past and half past, or about twenty past or even it's monday afternoon are good enough answers most of the time.

so the 5% & 7% if they are proved in the future to actually be 4% & 5% or 6% & 8% I will be happy that my answer was "in the parish".

Supp bonding might just be worthwhile especially ifyou or yours are the odd one that might just benefit from it.

 

[DetlefSchmitz]

(from original misquoted report)

Summary
This report contains a review and analysis of the results of tests conducted on RCDs installed in domestic properties to determine if they would operate in the specified time when tested at 30mA and/or 150mA. 607 electromechanical RCDs were tested in properties in the UK owned by Housing Associations and Local Authorities.
Six RCDs were found to have been shorted out to avoid what was perceived to be nuisance tripping. If these six RCDs are left out, the pass rate was 97.2%.
All of the RCD were installed in distribution boards. None of the occupiers operated the test button on the RCD to check that the RCD was working correctly.
Samples of the failed RCDs were returned to ERA for examination. It was concluded that the RCD faults could have been detected if the occupier had operated the test button on the RCD.
ERA strongly condemns the practise of shorting out RCDs to avoid nuisance tripping. This act renders the RCD useless and leaves the occupier exposed to a risk of injury from fire or
electrocution.

So of these supposed 7%, 4.3% were incorrectly installed, and the others could all have been discovered to be faulty by operating the test button.