bonding services

[JUD]

when you main bond services, does this not take away the need for supplementry bonding.......???? is what i believe but hesitant now....

As I understand it, supplementary bonding is used to limit the potential difference between exposed or extraneous-conductive-parts to ≤ 50V.

The impedance between any exposed or extraneous-conductive-parts should be low enough to meet the above requirement.

Let's say you have a 7kW shower on a 32A Type B breaker. The current required to operate the breaker is 160A so the impedance between the exposed-conductive-part of the shower and any other exposed or extraneous-conductive-parts of the location should not be more than 50V ÷ 160A = 0.31Ω.

This may not be achievable through main protective bonding alone so supplementary bonding is used. Of course RCDs do away with the need for supplementary bonding in most cases as the maximum impedance increases to 50V ÷ 0.03A = 1667Ω

 

[davie spark]

You crimp a 'doubled over' 10mm2 conductor? In what, a 25mm2 lug? I'm not convinced that will be a reliable connection. Also you're not following the MI for the lug so therefore in breech of BS7671.
As I said above, nothing to stop you cutting the bonding cable and fitting two 10mm2 lugs then loop to the next service. There's a warning label in place at each location to warn about removal.

Yeah, your right it would be awkward to do, might possibly be a struggle but managable to double over a 6mm but not a 10mm so that would indicate the need for two separate conductors. As for cutting the cables, I don't have B.S.7671 in front of me at the minute (which is particularly annoying when you offer advice on this forum only to find someone else who IS sitting with a copy, ready to pounce on you should you suggest advice which is above the minimum standard of the regs), I seem to remember that if you daisy chain a bonding conductor you are not allowed to cut it so that if the first connection IS removed for whatever reason, the conductor by virtue of being continuous ensures that the second bond is still functional. Whereas if it's cut and the first bond is disconnected, neither bond will be functional.

 

[i=p/u]

showers are class 2 construction tho??? does this make any difference jude??

 

[IQ Electrical]

There isn't a regulation saying continuous conductor, it's Guidance Note 8 recommendation, I think I posted the exact wording somewhere in this thread.

 

[IQ Electrical]

it says in chris kitchers book max lengths of bonding conductors ,10mm 27M, 16mm 43M.. so doesnt exceed 0.05 and you saying he is wrong.... i thought was great book too...

Yes, he's wrong, read this thread http://www.electriciansforums.net/e...o-you-work-out-when-go-up-10mm-16mm-so-4.html and find the email from Paul Bicheno from the IET on this very subject.

There is clarification on the 0.05 figure in the new Guidance Note 3 and 8 but you'll have to wait a few months still lol!

 

[JUD]

showers are class 2 construction tho??? does this make any difference jude??

Just using it as an example.

I'm sure you know what I mean.

 

[i=p/u]

yeah but i wan to know this stuff inside out , so many overlapping effects one reg has on another... rcd rcd rcd forget it all

 

[davie spark]

There isn't a regulation saying continuous conductor, it's Guidance Note 8 recommendation, I think I posted the exact wording somewhere in this thread.

That's been the basis of some of the replies I've posted on here 'recommendation' however there are one or two' Regsophiles' on here sitting with their laptop set in 'pounce mode' which is a bit sad and off putting. I can't imagine a life where I'd be sitting at home AFTER WORK with a copy of B.S.7671 open ready to save the cowboy world when I could be watching SKY SPORTS HD. I might join in though when I'm at work if I've got the time.

 

[IQ Electrical]

That's been the basis of some of the replies I've posted on here 'recommendation' however there are one or two' Regsophiles' on here sitting with their laptop set in 'pounce mode' which is a bit sad and off putting. I can't imagine a life where I'd be sitting at home AFTER WORK with a copy of B.S.7671 open ready to save the cowboy world when I could be watching SKY SPORTS HD. I might join in though when I'm at work if I've got the time.

This is a great forum and people tend only to 'pounce' when homemade reg's are quoted and that's because many use the forum for exam revision etc. and it doesn't help when opinion is quoted 'as a regulation'.

As for sitting with open books, I think many here quote from memory alone, there is some excellent knowledge and experience on this forum and it's all free lol!

 

[i=p/u]

your lucky you have a job if on your doorstep, if not on your doorstep you not lucky, so yesy some of us are sad we have no work and waqnt to keep her lit, my woman thinks im bonkers chatting about electric every evening these days but im on level 3(3rd year) 17th edition in 2 weeks and 2391 in january(i think) i dont waste money so they can correct me all they want, when there in the game like yourself probably for years , its second nature... give a little daveeeeeeeeeeeee.pls and stop judgin others, people do what they want to do as you know, im gonna sleep with regs tonight and see if spirts and can weep it from book into my brain

 

[IQ Electrical]

your lucky you have a job if on your doorstep, if not on your doorstep you not lucky, so yesy some of us are sad we have no work and waqnt to keep her lit, my woman thinks im bonkers chatting about electric every evening these days but im on level 3(3rd year) 17th edition in 2 weeks and 2391 in january(i think) i dont waste money so they can correct me all they want, when there in the game like yourself probably for years , its second nature... give a little daveeeeeeeeeeeee.pls and stop judgin others, people do what they want to do as you know, im gonna sleep with regs tonight and see if spirts and can weep it from book into my brain

Now if I did THAT I'd be swapping my reg's for The Big Issue!

 

[davie spark]

Sorry i=p/u, I hope you absorb the 'power' soon, good luck the your course. It's not all 'SECOND NATURE' as you think, especially after the introduction of the 17th changes and the imminent amendments to B.S.7671 and 2391 etc. Sleeping with the book won't work you'll have to do what the rest of us do and read it. Luckily for you, you are still being taught it. The fact that you are on this forum frequently asking questions is commendable for someone in 3rd year, you are a role model. You'll soon be answering the questions.

 

[GaryM]

That's been the basis of some of the replies I've posted on here 'recommendation' however there are one or two' Regsophiles' on here sitting with their laptop set in 'pounce mode' which is a bit sad and off putting. I can't imagine a life where I'd be sitting at home AFTER WORK with a copy of B.S.7671 open ready to save the cowboy world when I could be watching SKY SPORTS HD. I might join in though when I'm at work if I've got the time.

Sorry you feel that way Dave. Personally I don't have BS7671 sat open at the side of me (it's in the van) though I do have a PDF on my computer. I wouldn't say I'm pouncing by quoting any of it in any posts I make, it's more a case of offering help and not points scoring as I'm a little past that now!

 

[i=p/u]

come on dave im awnsering the easy ones already, but have to admit i dont care there first as there is pouncersLOL, SOON THEY WILL BE DESTROYED!!!!

 

[davie spark]

come on dave im awnsering the easy ones already, but have to admit i dont care there first as there is pouncersLOL, SOON THEY WILL BE DESTROYED!!!!

May the force be with you and when it is you should change your log in to F = qvB sinθ.