S
Silly Sausage
... diagonally opposed to each other ...
I think you mean diametrically. :shades_smile:
... diagonally opposed to each other ...
Just because there is no visual sign of supplementary bonding doesn't mean it isn't there. There is no requirement for the terminations to be accessible or visible, therefore an assumption can be made that supplementary bonding is present and adequate if R≤50V/Ia. The lack of RCD makes for a C3 only.
A supplementary bonding conductor is not a protective bonding conductor.
It is not there to equalise the potential between exposed and extraneous conductive parts in the event of a fault, it is there to supplement the main protective bonding in its duty of equalising the potential between parts.
BS7671 doesn't define a supplementary bonding conductor as protective, because it isn't! Lol
I think this is where the flaws in your understanding of its purpose stems from.
The application of a supplementary bonding conductor is to add to the protection given by a main bonding conductor, a supplementary bonding conductor on it's own has no application whatsoever.
And that my friend is the crux of the matter really isn't it!
Hard to see why others seem to struggle with this concept!
DSkelton
Incorrect Regulation 543.2
I disagree
Incorrect Page 157 BGB
I disagree
It's there to reestablish the equipotential zone, hence why its referred to in 701.415.2 as LOCAL SUPPLEMENTARY BONDING!
I disagree, the equipotential zone should already be there, it is there to supplement it
Example, Ze 0.02,Circuit to bathroom, 4mm twin earth, cpc 2.5, 25 meters long, Exposed conductive part and extraneous conductive part with the bathroom, whats the touch voltage?
50V?
Again, strange that, i assume you will be utilising 543.2
No, I'll be utilising the oxford english dictionary definition of supplementary
Completely wrong, take the bathroom example above, upon fault a voltage will appear on the exposed conductive part, if this is supplementary bonded to the extraneous part then the touch voltage will be dramatically reduced.
I disagree
Read 700 General BGB, page 197
The special locations in part 7 supplement or modify the general requirements
So we meet 415.2 as required and then we modify and supplement with the requirements of 701
And your point is?
If you don't know the answer to the touch voltage, its 135 volts, but that's okay it meets 50/Ia.
Huh, maximum touch voltage is 50V??? It is the maximum allowed fault voltage that could appear on exposed metal work if their were a earth fault on that circuit before the protective device operates.
That's why we apply LOCAL SUPPLEMENTARY BONDING!!
No, we apply it to SUPPLEMENT the existing main protective bonding.
There are a host of other issues, i'm not going into anymore, i suggest you speak to the IET because what you are suggesting may put lives at risk!!!
Haha, will it? Really? Funny that, because the IET seems to agree with me on this subject?!
Chris
Just because there is no visual sign of supplementary bonding doesn't mean it isn't there. There is no requirement for the terminations to be accessible or visible, therefore an assumption can be made that supplementary bonding is present and adequate if R≤50V/Ia. The lack of RCD makes for a C3 only.
Taking 526.3 & 543.3.2 into account, and BS951 clamps are of a non MF nature; if SB wasn't visible on a decent install, I would say it is fair enough to assume that there isn't any.
fantastic technical debate , chapeau to all contributing parties.
but like most epically long threads , the original question is lost , so im going back to read it again.
yep , its still clear.
an inspection carried out at a private dwelling highlighted multi non rcd protected bathroom circuits.
no local supp. bonding was visually evident at any accessory or any exposed metalwork.
its a C2 all day long.
unless someones trying to suggest , in the complete absence of any official guidance whatsoever , is that once supp. bonding cant be visually confirmed , that the inspectors next step is to start randomly carrying continuity tests between bits of metal in the bathroom , in the hope that good readings can now justify a defect reduction to C3 ??
get real.
;-)
Yep C2 is what i have always attributed to a situation like this.....
Biff may I point you to this part (high-lighted in the text), which was the guidance issued by the ESC, albeit not in the BGB.
This was in the older version of the BP guides, I will have a look and see if it is in a newer version.
415.2.2
Where doubt exists regarding the effectiveness of supplementary equipotential bonding, it shall be confirmed that the resistance R between simultaneously accessible exposed-conductive parts and extraneous conductive parts fulfils the following criteria:
R< or = to 50V/Ia in AC systems
Where Ia is the operating current in amperes of the protective device - for over current devices the current causing the automatic operation in 5s.
see above, that's exactly what BS7671:2008 states, if this has changed in the update then fair enough, but I'm not aware of that change... sure someone who hasn't had the BGB nicked by their spark will confirm it one way or the other.unless someones trying to suggest , in the complete absence of any official guidance whatsoever , is that once supp. bonding cant be visually confirmed , that the inspectors next step is to start randomly carrying continuity tests between bits of metal in the bathroom , in the hope that good readings can now justify a defect reduction to C3 ??
get real.
;-)
see above, that's exactly what BS7671:2008 states, if this has changed in the update then fair enough, but I'm not aware of that change... sure someone who hasn't had the BGB nicked by their spark will confirm it one way or the other.
Biff may I point you to this part (high-lighted in the text)
Note: where the presence of supplementarybonding cannot be confirmed by inspection, it
may be verified by a continuity test ** (< 0.05 ohm) **
Between pipework and metal light carcass **0.44ohms
Between pipework and downflow heater circuit cpc** 0.26ohms.
cheers, so what's the chances of this now being settled then?Still in the BGB mate.
Supplementary bonding shall be provided by a supplementary conductor, a conductive part of a permanent and reliable nature, or by a combination of these.
.... so what's the chances of this now being settled then? ......
You must apply 415.2 unless the three conditions are met.Geoff or DSkelton is wrong merely that there interpretation seems to miss the point that section 7 of BS7671 asks for SB to be applied if the 3 conditions are not met.
Nooooooooooooooooooooooooooooooo. You cannot end it on such a flawed statement.
You must apply 415.2 unless the three conditions are met.
This is not an interpretation; that is what it says.
All RCBOs are RCDs but not all RCDs are RCBOs.
Makes u wonder. If us qualified experienced electricians have different views. How does a Electrical Trainee think :-(