EICR and Supplementary Bonding.

[Geoffsd]

415.2.2 states that SB is effective if R≤50/Ia

Agreed

But you don't agree that if the R is already ≤50/Ia no more bonding is required. Why would it be?

______________

and
542.2.1 states that a fixed conductor or an extraneous part may be used as a SB conductor so if the parts already satisfy R≤50/Ia then 415.2.2 is met and no Supplementary(additional) Bonding is required.

How do you intend to apply that to the requirements of 701? The SB is required to be connected to the Protective Conductor Terminal of the location? And i assume 543.2.1?

I'm not sure what you mean by keeping asking about 701. That's what we are discussing.
If not required for the above reason then it does not apply.
543.2.1 merely lists parts which may be used as bonding including an e-c-p (pipe) and fixed conductor (cpc).

________________

This would seem to be the only thing we do disagree about so I will ask again - if this is not so and SB must be applied regardless thus reducing the impedance to negligible why is 50/Ia ever mentioned?

Not too sure what you mean, i think you need to be specific with regard the installation. If we take an agricultural location 705,say a large metal shed, if two conducive parts are effectively connected do we need to SB the two, no, your interpretation in that instance is correct, but not with regard 701.

What I mean is - you are stating that SB must be applied (where I think not) in which case the resistance between the parts will always be near negligible so why did they think up the 50/Ia rule. In your world the bathroom would need to be massive to get anywhere near 50V.

________________

With only a lighting circuit in the room and all parts connected by up to 5m. of 4mm² the touch voltage would only be 30x0.023 = 0.69V.
Even with a 40A shower it would only be 200x0.023 = 4.6V.

What if a greater current was to flow through the bonding conductor

That's not the purpose.
All we have to consider is the greatest Ia of the bathroom circuits.
That is the highest current that may flow from a touchable exposed part before the disconnection of the current - 5x6A for lighting or e.g. 5x40A for shower.
To ensure the voltage drop from this exposed part to another part that may be touched is a maximum of 50V, therefore 50V/If ≥ R

________________

So why is the limit set at 50V when this would never occur if everything must be bonded regardless?

Belt and Braces, ensuring no fortuitous connections, and as you have stated 50 V is what they regard as safe

Then why, if that is already met by the installation, are you insisting on reducing it further with additional supplementary bonding which is not required.
The fortuitous connections to which you refer are the very parts to which you want to connect the extra un-required bonding.

 

[D Skelton]

As it is a special location 701.415.2 states that -

Local SEB ACCORDING TO 415.2 shall be established...

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!

 

[Badged01]

I think the thread is going around and around in circles. Two views diagonally opposed to each other -- other than on agreement that 701 & 415 need to be applied in a special location (bathroom).

Enough information from both viewpoints available in the thread for anyone interested in the requirements for supplementary bonding to make their own informed decision!

Can I suggest the thread has run its course and is closed by the moderators??

 

[telectrix]

mods are too busy measuring resistances in their bathrooms.

 

[Badged01]

Excellent, hopefully the mods will then be able to give their own independent assessment based on their field investigations/findings!

 

[Silly Sausage]

... diagonally opposed to each other ...

I think you mean diametrically. :shades_smile:

 

[Badged01]

Definately not in this case, we are applying it to supplementary bonding and there needs to be a physical connection

 

[Chr!s]

DSkelton

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.

Incorrect Regulation 543.2

A supplementary bonding conductor is not a protective bonding conductor.

Incorrect Page 157 BGB

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.

It's there to reestablish the equipotential zone, hence why its referred to in 701.415.2 as LOCAL SUPPLEMENTARY BONDING!

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?

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.

Again, strange that, i assume you will be utilising 543.2

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.

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.

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!

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


If you don't know the answer to the touch voltage, its 135 volts, but that's okay it meets 50/Ia.

That's why we apply LOCAL SUPPLEMENTARY 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!!!


Chris

 

[D Skelton]

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

........

 

[Jay Sparks]

Definition of supplementary in English:


supplementary

Line breaks: sup|ple¦men|taryPronunciation: /ˌsʌplɪˈmɛnt(ə)ri
/
ADJECTIVE

• Completing or enhancing something:the programme offers supplementary information about the newsthe development of databases supplementary to existing ones
• SYNONYMS
• additional, extra, supplemental, increased, further, more; add-on, complementary, subsidiary,accessory, auxiliary, ancillary, supportive, reserveView synonyms
  appended, attached, added, extra, accompanying, annexed, adjunctView synonyms
  
  
  

 

[Silly Sausage]

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.

 

[spark 68]

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.

Interesting point Re-accessibility Archy 526.3,

The 15th ed 526 refers to non-flexible cables, or a joint between a non-flexible and a flexible cable, that edition also specifically excludes protective conductors in 527 (more about containment and enclosure in building fabric etc.)

In the 16th amd 2 526-03 refers to specifically to live and PEN conductors, and connections in an enclosure, 526-04 is about general accessibility of connections in that edition, so that is similar to the 17th. in that respect. 527 is mainly about fire propagation in that edition.

So while inaccessible sup bonding my not comply with the 17th, it may do with an earlier edition, the 16th underwent several re-writes too

We have all come across bonding clamps under the floor boards and behind sink units, under baths etc. at one time or another.

If a decent install complied to an earlier edition and tested out ok between ECPs I would assume it was fitted, after all we are often told on here that before the advent of the Electrical Trainee the sparks of the time were superior in every way. lol

 

[Guest55]

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.
;-)

 

[rattlehead85]

Yep C2 is what i have always attributed to a situation like this but when i was cross examined by somebody who claimed it was only a c3 coz the readings i obtained where acceptable i started to question my own judgement to the point where i thought i had it wrong!!
Good debate this which gave some interesting points of view.

 

[spark 68]

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.
;-)

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.