bonding gas and water how do you work out when to go up from 10mm to 16mm and so on

[chopper]

were currently doing a job in massive old pub whats going to be a libary, my gaffer says put 10mm bonding to gas and water but how do you actually work out what size is required

 

[IQ Electrical]

Re: bonding gas and water how do you work out when to go up from 10mm to 16mm and so

:smile5:Morning:smile5:

IQ - Thanks for your patience. I hope you're not too jaded covering something you've clearly been over before, so thanks for bearing with me. I just wanted to understand why you said what you said, as, has been pointed out by several other (learned) members, and time served sparks I know, they all believe it to be so (the 0.05 Ohms or less for the main bond...etc etc). And also, recently, as BruceLee points out, on 2391 courses (was taught this on mine a few years ago too, and it was in all the text books I fervently acquired ....)

HOWEVER! I have stuck with it, re read it, re re read it, and I agree with you!

It is a very poorly written piece of English. Its a tricky language sometimes and to get to the bottom of it (what is written) requires a clear head and a freshly woken up mind.

I have it now. The text does as you say require 0.05 or less between the MET and the bonding conductor. Or other examples. It does not say (As I believed and have been led to believe by lecturers, text books, etc like Christopher Kitchers) that the, for example, disconnected (with a safely isolated installation of course) 88 metre run of 10mm2 main bond from one end to tuther has to be 0.05 or less. At last. I am with you!

You move in higher circles than me btw. I suspect you are a learned fellow. Again, thank you for your patience :mad2:

It's a poor piece of text that divides opinion but it's one of the points that should really be black and white.

It's often a criticism that BS 7671 is open to interpretation and indeed it is but that is because it is written to be interpreted by competent persons on an infinite range of scenarios that could not possibly all be catered for.

I bet we move in the same circles, the IET just wanted a contractor's input for the Guidance Note amendments

 

[Engineer54]

Re: bonding gas and water how do you work out when to go up from 10mm to 16mm and so

It's a poor piece of text that divides opinion but it's one of the points that should really be black and white.

It's often a criticism that BS 7671 is open to interpretation and indeed it is but that is because it is written to be interpreted by competent persons on an infinite range of scenarios that could not possibly all be catered for.

The 14th edition managed it, ...but then that was the last Reg edition that was written in Plain English!! lol!!

Now, since the Reg's becoming a BS, a higher legal form of English has been applied, which can and often does confuse issues, ...ie, open to interpretation. There are quite a few areas where the IEE needs to go through and clean up passages. Many should have been sorted out ages ago, even if it was just as an on-line addendum/correction sheets, that could wait till the next revision issue to be included...

 

[Chr!s]

Re: bonding gas and water how do you work out when to go up from 10mm to 16mm and so

Hope this helps, this is an email i sent a while back and one received from the IET.

Hi

Hope you can clarify a issue.

Main protective bonding and its maximum length.

My understanding in general installations TN at 230 v we need a disconnection of 0.4 seconds as part of ADS, bonding needs to be sized as per Reg 544, and as such
there is no restriction upon length, this id due to the fact we have no limit on touch voltage assuming we meet the prerequisite of ADS.

If there is a limit on touch voltage in a general installation which regulation places this limit?

The only limit i see on main protective bonding is that of 415.2.2, this is additional protection and used in locations of increased electric shock. This is shown in Reg
701.415.2 (Note). Where we check the effectiveness of the main protective bonding utilizing 415.2.2.

There is a passage in GN3, though in my opinion the 0.05 ohms is clearly a value for measuring between to points where bonding clamps can not be removed for
example, not applied to the overall length.

Ive looked in GN8, GN5 and BS7430 and i see no limitation other than CSA or when additional protection is required.

Ive spoke to ECA and they are of the same mind, in that in general installation no limit is placed on the length of main protective bonding.

Its probable that many installations have circuits that would drop more than 50v across R2 alone, my understanding is this is ok providing we meet the requirements of
ADS, if additional protection is required then 415.2.2 applys.

Many thanks, hope you can clarify.

Regards Chris

Reply

Hello Chris,

I am required to preface my remarks by saying that I have no authority to interpret the requirements of BS 7671:2008, Requirements for Electrical Installations.
The interpretation of BS 7671 is one of the roles of the Joint BSI/IEE Committee JPEL/64. However, within that constraint, I hope you will find my comments helpful.


BS 7671:2008 does not have requirements that limit the length of a protective bonding conductor. Chapter 41 is based on the fundamental requirements of BS EN 61140 (Refer to Section 410) which includes reference
To the conventional touch voltage limit of 50V. The key technical intent is to meet the requirements for fault protection 411.3 covering protective earthing, protective equipotential bonding and automatic disconnection. Typically you would look to achieve the appropriate disconnection. If disconnection cannot be achieved in the appropriate time then Regulation
411.3.2.6 requires the appropriate supplementary bonding in accrodance with
Regulation 415.2.

GN3 includes reference to 0.05 ohms but this is more to do with proving there is an actual connection between two points rather than making any
Judgement on length. GN3 is currently being updated to clarify this.



Regards
Paul Bicheno
Standards and Compliance
The IET

 

[IQ Electrical]

Re: bonding gas and water how do you work out when to go up from 10mm to 16mm and so

Hope this helps, this is an email i sent a while back and one received from the IET.





Reply

Where the heck have you been lol?
That puts it to bed

 

[SPARTYKUS]

Re: bonding gas and water how do you work out when to go up from 10mm to 16mm and so

Wow Chr!s wish you'd posted that a few days ago you'd have saved me a few hours trawling thorugh OSG/BRB/GN3/GN8 trying to prove IQ wrong :bigcry::earmuffs:

(just kidding IQ)

 

[Chr!s]

Re: bonding gas and water how do you work out when to go up from 10mm to 16mm and so

Where the heck have you been lol?
That puts it to bed

Hello IQ, yes its been a while, not had much chance of late to post, hardly stopped for breath lol

There is a thread somewhere covering this issue, ill try and find it.

Hopefully GN3 will be a little clearer, its confused many, including a lot of 2391 lecturers who used the .05 figure when teaching students.

Regards Chris

 

[Chr!s]

Re: bonding gas and water how do you work out when to go up from 10mm to 16mm and so

Wow Chr!s wish you'd posted that a few days ago you'd have saved me a few hours trawling thorugh OSG/BRB/GN3/GN8 trying to prove IQ wrong :bigcry::earmuffs:

(just kidding IQ)

Yes, you will do well to trip IQ up

 

[Chr!s]

Re: bonding gas and water how do you work out when to go up from 10mm to 16mm and so

The thread was "general testing questions" not sure how to place a proper link.

Pushrod had a reply from Richard from the IET, Richard has the job of updating GN3. His reply followed that of many, that of the 0.05.

Since then This has been clarified and the above reply from Paul is the approach which will be clarified in the new GN3.

Regards Chris