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Discuss supplementary bonding in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

M

MTI

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hi all, just trying to clear things up. read various articles including regs and osg but having major arguments with someone about supp bonding. basically, im told if all final circuits on rcd etc, all disconnection times met and all other various rules in regs met then no supp bonding is needed at all? can anyone clear this up please? im not only talking about between bath. lights and and shower etc but also metal work.

i feel this will go on a bit hehe!

other argument is if something happens to affect mains bonding or it degrades etc. then what? all means of earthing is lost completely.

for the sake of this argument, lets say we have ALL pipes and joints etc in copper with NO plastic joints in any parts of the systems....

who will start us off? down to descretion of spark on site too?
 
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sparks1234

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Arms
Main bonding should be in place. If all circuits in or passing through bathrooms are on RCD then supp bonding is not necessary
 
M

MTI

  • Thread Starter Thread Starter
  • #3
thats what i said but my mate is barmy! i suppose its down to descretion but the book says it! although its not mandatory too! i have heard some daft court cases and people been let off as nobody could hold anything against them barring poor workmanship etc
 

Des 56

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Arms
Esteemed
other argument is if something happens to affect mains bonding or it degrades etc. then what? all means of earthing is lost completely.

The supplementary bonding is more to ensure equipotential bonding, than act as some form of secondary standbye main protective bond
As long as the four conditions are met then its not required
Many seem to just assume that its no longer required but that is not the case
 
M

MTI

  • Thread Starter Thread Starter
  • #6
you say four conditions-i see where you are coming from but if four are met then you say not needed.ok i understand that but then you say people believe its no longer required and not the case?

so ok, i do full rewire or new build and all rcds in place, mains bonding in place, disconnections met etc. is it still needed? can you please try and clear up as to when it would be needed? cheers for the help so far, martin
 

Des 56

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Arms
Esteemed
701.415.2 (1) (2) (3) + by assessing 415.2.2


Quoted by sparks 1234
is that really your age??

Nice reply
Bit of unwanted sarcasm but
Ex screwfix member perhaps?

Conversations were interesting on this forum
Will post post in the distant future
Bye
 
Last edited:

andyb

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Arms
Esteemed
Supplementry bonding may be omited where all all the following conditions are met.

1/ all circuits meet automatic disconnection times

2/ all circuits protected by rcd

3/ all extraneous conductive parts connected to protective equipotential bonding

If any of the above are missing, then bonding is required.

Incidentaly, I had my assessment on Monday and the assessor made me prove No 3 of the above.
 
D

daver

  • Thread Starter Thread Starter
  • #10
Just carry out IR test on the exposed part and a known earth. If reading is .02 M ohm or greater, then not required.
 

andyb

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Arms
Esteemed
Just carry out IR test on the exposed part and a known earth. If reading is .02 M ohm or greater, then not required.
True, if it's greater than 22k ohms then it is not classed as an exraneous conductive part.
 

diditrain

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Arms
Determining if a part is extraneous, or just a piece of metal


A test should be made using an insulation resistance tester set to the mΩ range, supplying 500volts.

Connect one test lead to the metal part in question and the other lead to a known earth. If the resistance value is 0.02 mΩ (20,000Ω) or greater, no supplementary bonding is required. If less than 0.02 mΩ, supplementary bonding should be carried out.

If we use Ohm`s law we can see how this works:

V
— = I:
R

500
— = 0.025 A
20,000


This shows that a current of 25 mA would flow between the conductive parts;
This would of course only be 0.012 amp if the fault was on a single phase 230 volt supply. This current is unlikely to give a fatal electric shock. I believe that 0.01 is the no let go threshold, but someone may correct me.

The test must not be confused with a continuity test. It is important that an insulation resistance tester is used.

I am not laying credit to this piece of work, therefore please do not accuse me of plagiarism, because I do not know how to cite correctly. The book I seen it in was by Christopher Kitcher

Hope it is useful to others who were as confused about this issue as i was
 
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