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Topic Title: Cross bonding
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Created On: 08 January 2013 09:11 PM
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 14 January 2013 12:51 PM
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marclambert

Posts: 311
Joined: 23 June 2010

Back to the OP.
Some boiler manufacturers require "cross bonding" to incoming pipework. Even though the pipes are connected to a common brass manifold with compression fittings. Which is obviously a better conductor than a bit of 4mm! If you ring them to ask why they put it in the instructions..surprise surprise they can't tell you why!
So my answer would be, if it's in the manufacturers instructions and it makes the customer think they're getting value for money, then fine go ahead and do it. As they are all already connected you are not making the situation any worse (or better)
Did anyone think to ask David 911 to write a book about this
Regards
Marc
 14 January 2013 01:12 PM
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AJJewsbury

Posts: 11587
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I thought I covered mixed disconnection times and RCD's in my post Andy.

You did, I was just worried about people reading the "1667 Ohms" bit out of context - the regs don't directly say 1667 Ohms, just 50V/Ia without being at all clear which device's or devices' Ia it's talking about. A lot of people seem to think that they only need to consider bathroom circuits, hence only think about 30mA RCDs, and then get the meter out, measure something below 1667 and say the requirements for supp bonding are met.
- Andy.
 14 January 2013 03:21 PM
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Parsley

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Originally posted by: AJJewsbury

I thought I covered mixed disconnection times and RCD's in my post Andy.


You did, I was just worried about people reading the "1667 Ohms" bit out of context - the regs don't directly say 1667 Ohms, just 50V/Ia without being at all clear which device's or devices' Ia it's talking about. A lot of people seem to think that they only need to consider bathroom circuits, hence only think about 30mA RCDs, and then get the meter out, measure something below 1667 and say the requirements for supp bonding are met.

- Andy.



I think that includes the NIC as well Andy.
http://www.niceic.com/en/account/media/17thpg1and2.pdf
See note bottom of page 1.

I was given an NIC learners guide when I did the 17th with them in 2008, it states all circuits in the location must be RCD protected and uses 50V/Ia 30=1667. There's no thought about circuits outside the location as far as I can see.

Regards
 14 January 2013 05:10 PM
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AJJewsbury

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I think that includes the NIC as well Andy.



Looks like they've got the main bonding bit wrong as well - they say "the installation is fitted with effective protective main equipotential bonding" whereas the regs say "All extraneous-conductive-parts of the location are effectively connected to the protective equipotential bonding".

Oh, and half of their window recess seems to be colour coded for the wrong zone.

Then they wonder why we prefer to do our own thinking...

- Andy.
 14 January 2013 08:27 PM
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ebee

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I thought they did not allow us to do our own thinking.
Whoops there`s me thinking again.
Sorry


-------------------------
Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 15 January 2013 10:52 AM
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MrP

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God forbid Andy are you saying the NICEIC got something wrong you will tell me next that the NICEIC imply the DI box should be ticked if you fit one of those fancy plastic light fittings

MrP
 15 January 2013 11:30 AM
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OMS

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Imply ? - they have a whole DVD that covers why the NICE people think you should tick the box if class 2 luminaires are installed

Regards

OMS

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Failure is always an option
 18 January 2013 11:28 AM
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marclambert

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Another oddity from the NICE people is that "overfusing" a cable should be a C2. Whereas an open RFC is a C3?
According to the latest guidance on completion of the EICR from the NICE website.
I stand to be corrected but aren't the two examples of the same thing?
 20 January 2013 10:48 PM
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Westonelectrical

Posts: 85
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Originally posted by: geoffsd

There is no requirement to connect supplementary bonding to the MET.



There is no requirement to 'cross bond' (as in the meaning in this thread).


Not even bonding between plastic pipe fittings... I recall it saying that??
 21 January 2013 03:52 PM
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geoffsd

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I'm not sure of your meaning.

Do you mean around plastic fittings?

You recall what saying what?
 22 January 2013 12:52 PM
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mark2spark

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My mate that does house bashing informs me that they don't even run a 10mm from the CU to the incoming water pipe these days, - and haven't for some time.
"What's the point?" is the reasoning. Well, errr, yes, what *is* the point in bonding 2 inches of copper pipe between plastic fittings/pipes?

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I am prone to talking complete bol***ks at times, please accept my apologies in advance.
 22 January 2013 06:44 PM
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geoffsd

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Originally posted by: mark2spark

My mate that does house bashing informs me that they don't even run a 10mm from the CU to the incoming water pipe these days, - and haven't for some time.

"What's the point?" is the reasoning. Well, errr, yes, what *is* the point in bonding 2 inches of copper pipe between plastic fittings/pipes?

I don't think the time is relevant.

In answer to your rather specific question, there is no point.

However, I presume this is not the only copper pipe in the installation.

If that which comes out of the ground is metal then it must be bonded.
Any other copper should be tested to determine if it is extraneous.
 22 January 2013 09:38 PM
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MrOther

Posts: 539
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Originally posted by: mark2spark

My mate that does house bashing informs me that they don't even run a 10mm from the CU to the incoming water pipe these days, - and haven't for some time.

"What's the point?" is the reasoning. Well, errr, yes, what *is* the point in bonding 2 inches of copper pipe between plastic fittings/pipes?


Are we saying that there is metal water incomer, a metal stub, then all metal?

If this is the case then depending on circumstance/use then maybe the reasoning is that incase the plastic piping is refurbed for metal then the metal is bonded?
 23 January 2013 12:32 PM
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mark2spark

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No, it's brand new housing, so a blue plastic water pipe comes out of the ground, there's a short bit of copper either side of the stop cock terminations, the plumbing installation then reverts to plastic.
It's been like that on sites for about 10 years or more now, but we still used to bond it because it was a trained monkey type of thing to do.
Gas is still bonded obviously.

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I am prone to talking complete bol***ks at times, please accept my apologies in advance.
 29 January 2013 10:29 PM
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Westonelectrical

Posts: 85
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Originally posted by: geoffsd

I'm not sure of your meaning.



Do you mean around plastic fittings?



You recall what saying what?



Must have read it wrong, I thought you you said no need too bond in between plastic pipes..
IET » Wiring and the regulations » Cross bonding

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