I am putting my house up for let and have had electrical and gas safety inspections done. The gas one was not a problem, one man came for about an hour and issued the certificate there and then. By comparison the electrics one has turned out to be a nightmare. Two men were at the house all morning and they found several things "wrong". One of the items was "No main earth to gas or water". Most of the water pipes are plastic but I now realise there were odd short lengths of copper like the washing machine pipes which were not earthed. I can rectify this but I don't know what they mean about the gas. I have visually checked and taken resistance readings on the gas pipes, meter and all the gas boiler pipework and everything shows earth continuity. The only thing I'm wondering is if these earth cables should go to an earth block outside the CU? They currently terminate at the earth block inside the CU. The earthing was also checked for the gas safety certificate and was passed.
Earth Bonding
- Thread starter fidom
- Start date
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H
holmslaw
..
Always find it amusing with people carrying out inspection and testing and not knowing the difference between exposed and extraneous conductive parts.
Who on earth (pardon the pun) would wish to EARTH water or gas services?
Bonding is not Earthing and Earthing is not Bonding.
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Agreed, but bonding something to something else which is earthed results in the first something being 'earthed', whilst earthing two things (to the same earth) results in them being 'bonded' - which is what results in a lot of the confusion, particularly given that when one bonds two things together, at least one of them will usually be 'earthed'!
In practical terms, the distinction obviously becomes relevant in terms of the sizing of the conductors, depending upon the reason they were installed.
Kind Regards, John.
Just to clarify, I'm not having a go at the person who posted up the thread but rather those who wrote the report and made nonsensical statements. These people should be competent to carry out the work and surely competent people should understand the difference, and indeed the requirements of the Wiring Regulations against which they are supposed to be assessing the installation!
Of course they should. I agree totally and, like you, certainly don't think that the OP deserves any criticism.
Kind Regards, John.
Here we go.
No - only parts that are earthed may need to be bonded.
No - they may still need to be bonded elsewhere.
No - they will each already be earthed.
Only if you want it to!
(Main) bonding is required to an e-c-p which may ('be liable to') introduce a potential - usually (but not necessarily) earth potential.
I don't understand your 'No', but agree that they might still need to also be bonded eleswhere (or more effectively - higher CSA).
As above, not necessarily. It is the fact that an extraneous-conductive-part may ('be liable to') represent a path to earth (or, exceptionally, a potential source of a non-earth potential) which creates the need for bonding. It is, after all, the fact that one of these 'already earthed' conductors might rise to above earth potential that results in the need for bonding; if one could guarantee (which one never could) that both would always be at true earth potential, there clearly would not be a need for any bonding.
Kind Regards, John.
Just 'liable to' and 'generally earth' so nearly always because it is earthed i.e. in the ground.
I was going to write "Yes but No". However if two parts need supplementary bonding (elsewhere e.g. bathroom) then I would consider that to mean that they are not bonded (satisfactorily).
Not necessarily - that would be supplementary bonding.
Again, just "liable to" not 'may be liable to' (does that mean definitely liable to i.e. probably does).
Otherwise - yes but that's the whole point?
Maybe I'm wrong, but I would take 'liable to introduce' to mean 'may introduce'. If I meant 'does introduce', I think I would say so!
My point was merely to indicate the reason for some of the confusion between bonding and earthing. As I said, if one 'bonds' to something earthed, then one is effectively earthing as well as bonding. If one earths two things by connecting them both to the same earth terminal (e.g. a MET), then one is 'bonding' them together, albeit not necessarily 'as well' (in terms in conductor CSA) as would be required by the regs for bonding.
Kind Regards, John.
An illustrative example has just occurred to me. A neighbour of mine has a metal oil tank sitting on a plastic/wood stand which is connected by a metal pipe (which does not go underground) into his house. I would personally say that should count as an e-c-p which needs main bonding, because it 'may' ('is liable to') introduce earth potential, even though it will not usually (if ever, certainly under dry conditions) introduce any potential. What would you say?
Kind Regards, John.
I would say he should make the whole lot live in case a bad man tries to steal his oil.
Jest ye not - it's a big problem in my part of the sticks. At least they haven't found a way of helping themselves to my LPG yet (although it might be fun to watch them trying!)!
Kind Regards, John.
I did say probably does.
One dictionary defines liable as 'given or inclined to' which I would take as more than 'may' (which the definitions do not use - (may, that is)). I would say likely to. I suppose we could have a few pages on this.
Yes that is obviously so but only exposed (already earthed) and extraneous (already bonded because liable to be naturally earthed) parts need to be bonded to equalise potential in fault conditions.
Assuming a correctly installed installation, if a metal part is not already bonded or earthed then it does not need to be bonded.
This is where you're confused - If two exposed parts are earthed it would be at the earth bar in the CU (to operate a CPD).
Extraneous parts connected to the MET would be bonded (to equalise potential in the event of a fault).
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