TNCS bonding for additions and alterations

Deleted member 9648 · Apr 29, 2016

Wonderwall said:
Does this thread not just prove, that the scenario of bonding water/ gas etc is extremely ambiguous throughout the electrical industry ?
I often come across the scenario where pipes are not bonded, and explain to the customer why I must carry this task out , and they always quite rightly, tell me they have stayed there for 40 years and had no problem. It's a minefield.
its makes us sparkies feel like we are creating work when all we are doing is try to confirm to the latest regs.
In my experience the test between any complete copper pipe pipe and an earth terminal is very low ohms. A fortitious earth no doubt.
I have never seen an earth clamp with charring on it. Ever . It should, if ever only carry some fault current, there is no serious load on it. If there is they have more serious problems surely.
Interested in other people's thoughts on this , as it's quite a bug bear of mine.
I have seen some installations where there is no earthing at all!! It has simply been disconnected or never been at all.
We then have to correct it, but it's not a one off scenario, I have seen it many times.

Not in the case of a TNCS system.
If you think about it the neutral is linked at the service head to a potential parallel path through bonded services which may well have a low resistance return path. Under load a very significant proportion of the neutral current may divert down that path.
I have never seen a bonding clamp with thermal damage either, and my argument is that a competent person should be able to make an assessment of the adequacy of undersized...(to present standards)...bonding which has nonetheless been satisfactory over many years.

Midwest · Apr 29, 2016

wirepuller said:
Common sense dictates that where a system has been in place for a considerable time with 6.0mm bonding, and is perfectly satisfactory without problems, then as long as an alteration or addition does not add a significant load then it will remain satisfactory.

I suspect this new guidance is part of the dumbing down of our industry. Because through no fault of their own those who have done the fast track courses do not have the knowledge to make those decisions, so the rest of us are not permitted to either .

In fairness wirepuller, I'm thinking THEY are actually agreeing with your statement.

The previous 'recommendation' was a carte blanche authorisation, for an electrician not to assess the condition of the installation. Now that decision has to be made locally by the electrician, involving knowledge and experience and a risk assessment process, and not some edict from a person sat in an office.
:thinking:

Of course there is another interpretation, in that their legal team have peered over their previous advice and seen that was not replicated anywhere in BS7671, which could make them responsible, should things go Pete Tong.

Deleted member 9648 · Apr 29, 2016

Midwest said:
In fairness wirepuller, I'm thinking THEY are actually agreeing with your statement.

The previous 'recommendation' was a carte blanche authorisation, for an electrician not to assess the condition of the installation. Now that decision has to be made locally by the electrician, involving knowledge and experience and a risk assessment process, and not some edict from a person sat in an office.
:thinking:

Of course there is another interpretation, in that their legal team have peered over their previous advice and seen that was not replicated anywhere in BS7671, which could make them responsible, should things go Pete Tong.

Good points....but the article seemed to make the case that if main bonding does not meet current requirements then no work should be carried out,no assessment etc....just no,full stop.

Midwest · Apr 30, 2016

wirepuller said:
Good points....but the article seemed to make the case that if main bonding does not meet current requirements then no work should be carried out,no assessment etc....just no,full stop.

The line given to me by Elecsa technical, was that it was the electrician to make that decision or risk assessment and that they weren't going to give everyone a get out of jail card, if you get my meaning.

Pete999 · Apr 30, 2016

Midwest said:
The line given to me by Elecsa technical, was that it was the electrician to make that decision or risk assessment and that they weren't going to give everyone a get out of jail card, if you get my meaning.

Some technical line that is then.