Discuss Cross bonding - 3 reasons why we don't anymore in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

E

ed-ectrician

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Hello there,

I am in college training and the bloke I work with gave me a question that he said NICEIC ask you during assessment - what are the 3 reasons why we do not cross bond anymore?

They were
1.Everything is protected by RCD now
2. You bond the main incoming gas and water so why bond everything to each other?

and I couldnt work out the third...

Any help please?

Also, is this even the case? I thought you had to cross bond in bathrooms and other special locations?!

Thanks
 
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E

ed-ectrician

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I am doing the 2330 I have done level 2. Doing level 3 next year! I have a regs book but it is at home and i wanted to know now!!

I have on site guide but no joy there as far as i could see.
 
E

ed-ectrician

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Do you not know then Jimmy Boy?
 

Jimmy Boy

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Arms
I am unsure as to how the exact wording of the question was presented to you ?
what are the 3 reasons why we do not cross bond anymore?

There are reasons why Equipotential bonding may be omitted but it is by no way a given.

They were
1.Everything is protected by RCD now..Really ? He must have a different regs book to us then
2. You bond the main incoming gas and water so why bond everything to each other?. Well because there may be a difference in potential between Extraneous conductive parts and exposed conductive parts ?

Also, is this even the case? I thought you had to cross bond in bathrooms and other special locations?! The answer to this is quite clearly stated in the OSG I found it in 5 minutes.:)
J








 
D

Deleted member 9648

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Are you refering to supplementary bonding?
 

darkwood

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Have regs book but at home and i wanted to know now!!! Classic!.... just got visions of OP spitting dummy out shouting I wanna know NOW!..

Clearly thats not the way it was written and no offense to OP just my weird mind lol
 

ruston

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Have regs book but at home and i wanted to know now!!! Classic!.... just got visions of OP spitting dummy out shouting I wanna know NOW!..



Clearly thats not the way it was written and no offense to OP just my weird mind lol



It' POETS day today you know, could be having a jar and a quiz lol.
 
E

ed-ectrician

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  • #10
I am unsure as to how the exact wording of the question was presented to you ?
what are the 3 reasons why we do not cross bond anymore?

There are reasons why Equipotential bonding may be omitted but it is by no way a given.

They were
1.Everything is protected by RCD now..Really ? He must have a different regs book to us then
2. You bond the main incoming gas and water so why bond everything to each other?. Well because there may be a difference in potential between Extraneous conductive parts and exposed conductive parts ?

Also, is this even the case? I thought you had to cross bond in bathrooms and other special locations?! The answer to this is quite clearly stated in the OSG I found it in 5 minutes.:)
J








I must admit i was a bit confused as i thought that the whole reason why you bonded stuff together was so no potential could exist in the event of fault conditions and simultaneously touching a metal sink etc. Not everything is attached to mains gas and water intake and also with resistance if it's miles away then you will have potential existing?!

This bloke's mustard so i reckon either i was not listening properly or he wasn't explaining himself. Most likely the former! He wouldn't make a mistake like that he's been in the game nearly 40 years and knows what he's doing.
 

ruston

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Supplementary bonding can be omitted a room containing a bath or shower if the regs in previous post are satisfied . I think this is what he was asking. Good luck with the course mate.
 
S

SirKit Breaker

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Supplementary bonding can be omitted a room containing a bath or shower if the regs in previous post are satisfied . I think this is what he was asking. Good luck with the course mate.
Other considerations maybe that the central heating system is piped in plastic, but has copper tails going through floorboards. So in effect the radiator cannot become live, if you supplementary bond it, then think about what could occur in a fault condition.

Cheers...........Howard
 

ruston

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Other considerations maybe that the central heating system is piped in plastic, but has copper tails going through floorboards. So in effect the radiator cannot become live, if you supplementary bond it, then think about what could occur in a fault condition.


Yeah good reason to get the wander lead out lol
 
L

Lucas

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  • #14
I'm probably wrong and only just thought of this but is it possible that the radiator COULD become live under fault conditions because the water that run's through the pipework is a conductor?
 
I'm probably wrong and only just thought of this but is it possible that the radiator COULD become live under fault conditions because the water that run's through the pipework is a conductor?
No.............................
 
E

ed-ectrician

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  • #16
Supplementary bonding can be omitted a room containing a bath or shower if the regs in previous post are satisfied . I think this is what he was asking. Good luck with the course mate.
What a legend thanks loads Ruston and thanks to everyone else who put in constructive comments! It feels good to help and instruct each other doesn't it?

Peace
 
W

wallyanker

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  • #17
I'm probably wrong and only just thought of this but is it possible that the radiator COULD become live under fault conditions because the water that run's through the pipework is a conductor?
I clearly remember my teacher telling us this aswell and I thought it wasnt correct and questioned him. He then went on about whats in the water and how that can conduct.. etc... wish I never ask...lol Still dont know if its true or not.
 

ruston

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I clearly remember my teacher telling us this aswell and I thought it wasnt correct and questioned him. He then went on about whats in the water and how that can conduct.. etc... wish I never ask...lol Still dont know if its true or not.

If you go on the IET site and search the "wiring matters" magazine . You will have to use the search because it was a few years ago , but there was an article of the conductivity of water in different regions of the UK.
 
A

aprillove1719

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  • #20
hi!!! what cross bonding are you referring to?
 
E

Edd

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......
 
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M

Mainman

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In BS7671, Appendix 6, you will see the Schedule for inspections for new installations (in the form of tick boxes). In the Left hand column at the bottom, the heading is "additional protection" and two methods are listed - Protection by RCD and Protection by Supplementary Bonding.

In the same column half way up, the heading is "Automatic Disconnection of Supply" and there you will see Supplementary bonding listed again

Additional Protection using RCD's or Supplementary bonding is where BS7671 state you must install it (Mainly found in Part 7 - including Locations containing a bath or shower)

Supplementary bonding by Fault protection can be used where disconnection times cannot be met and it is unreasonable to use RCD protection eg Industrial machines etc

Therefore Supplementary bonding has not been taken out, it's just the application of BS7671 on how its applied
 
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