17th edition bathroom eq. bonding wiki

[ebee]

I knew you would say that.

 

[Spark123]

It'd be useful to find a nice online 3D perspective drawing of the new zones...

Anybody come across one?

Had a little play about with the old card ones in ms paint:

Untitled

• Spark123
• 13 Sep 2008
• 1

Untitled

• Spark123
• 13 Sep 2008
• 1

 

[GaryMo]

Good job!

 

[JohnD]

"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%."

so where's the 7% failure rate?

 

[ebee]

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

"From the first phase it was concluded that:
Previous research published in Italy indicated that electromechanical RCDs had an average failure rate of 7.1%. However, if the RCDs were operated regularly by means of the integral test button, this figure fell to 2.8%, indicating that RCD reliability improved if they had been operated regularly "

 

[BS3036]

Mmm... I just looked at the actual report in question, which suggested a failure rate of 2.8%, ALL of which would have been detected by operating the test button.

I guess it's easy to mis-quote statistics.

 

[JohnD]

37% of all statistics are made up.

 

[ebee]

Mmm... I just looked at the actual report in question, which suggested a failure rate of 2.8%, ALL of which would have been detected by operating the test button.

I guess it's easy to mis-quote statistics.

The Italian one suggested 7.1% hence my approximation of 7%.
It was subsequently noted that if the test button was pressed regularly then this might well reduce to 2.8% but in my experience lots of folk do not do this regularly therefore 7.1% could often be more realistic for the majority of cases.
The difference probably indicates "stiction" being a major factor.
I don`t think that there is any suggestion that all of the 2.8% would have been detected by pressing the test button but I have no doubt that a small number might well have been.
Even if we get almost everybody to press regularly and get the figure down from 7.1 to 2.8 would you be happy.
I suggest a figure of in the region of 0.5% might be a reasonably happy figure here .
RCDs are wonderfull devices but do not rely on them, pretend they are not functioning and be carefull out there folks.

 

[BS3036]

I don`t think that there is any suggestion that all of the 2.8% would have been detected by pressing the test button but I have no doubt that a small number might well have been.

Quoting the report itself (quotation under fair quotation exemptions from copyright law)...

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.

It does appear that ERA trails of the report present a more sensational impression than the report itself.

 

[ebee]

I`m prepared to stand corrected then on that one.

It appears that the 2.8% is a total failure to operate then. worrying.
Failure must also include those when tested operate outside the required times/currents.
Perhaps that didn`t occour in this sample researched.

The Failure rate of 7.1% I believe came from Italian research and would include both failure to operate and out of spec but operating.

I think it rare that RCDs are oversensitive but sometimes leaky circuits tend to make them appear so - speaking purely electrically this is more of a nuisance than a safety issue.

Stiction does seem to be an issue here.
If 2.8% operate well outside spec or not at all that is worrying and if the figure might be around 7% ish to include those that stick and therefore delay due to non pressing of buttons then that is worrying too.

 

[Spark123]

Have been playing with the zones wiki, haven't made it live from the contents menu yet.
//www.diynot.com/wiki/electrics:speclcn:bathroom_zones
any comments?