Work on TN installations come "the 18th"

[JohnW2]

No-one yet seems to have offered any view/opinion on a question I posed in a recent thread (which perhaps became too long and tedious for most people to bother reading it!), and I would be interested to know what people think....

... after the appearance of "the 18th" in a week or two (or, I suppose, more correctly, 'afer its requirements become required' next January), do people feel that a combination of 132.16 (unchanged) and the new 542.1.201 will mean that work (any 'addition or modification') on a TN installation will only be able to be undertaken in compliance with BS7671 after an earth electrode has been installed?

Kind Regards, John

 

[EFLImpudence]

It depends what they initially meant by "adequate" and for what it has to be "adequate".

I doubt they have realised or remembered the connection between the two.

 

[Risteard]

They aren't going to require you to do something which was dropped from the final draft and only appeared in the Draft for Public Comment. (Not sure why you have wrongly assumed as fact that this is a pending requirement - I am reliably informed that it is not and will probably appear instead in the 1st Amendment. That said it's not a big deal as the rest of the world already installs Earth Electrodes in TN-C-S installations.)

 

[JohnW2]

It depends what they initially meant by "adequate" and for what it has to be "adequate". I doubt they have realised or remembered the connection between the two.

Indeed. In the other thread, an opinion was voiced that 'adequacy' can only be judged in relation to the requirements of current regulations (in which case it would be "not 'non-retrospective") - do I take it that you disagree with that view?

Kind Regards, John

 

[JohnW2]

They aren't going to require you to do something which was dropped from the final draft and only appeared in the Draft for Public Comment. (Not sure why you have wrongly assumed as fact that this is a pending requirement - I am reliably informed that it is not and will probably appear instead in the 1st Amendment.

Interesting. As you are presumably aware, throughout the thread which spawned this one (not to mention plenty of other threads), I liberally included the qualification "if it remains true to the DPC" - but I forgot to do so in this one. It won't be long before we know for sure, anyway. In any event, assuming that it is going to come (even if not until Amd 1), my question still stands.

That said it's not a big deal as the rest of the world already installs Earth Electrodes in TN-C-S installations.)

It's not the requirement (which, per DPC, would also apply to TN-S), per se, but the change to having such a requirement that could be a fairly 'big deal' - particularly if, as per my question above, it will mean for a few years that electrical work will very often have to start by installation of an earth rod.

Kind Regards, John

 

[ban-all-sheds]

It depends what they initially meant by "adequate" and for what it has to be "adequate".

I doubt they have realised or remembered the connection between the two.

542.1.201 The main earthing terminal shall be connected with Earth by one of the methods described in Regulations 542.1.2.1 to 3, as appropriate to the type of system of which the installation is to form a part and in compliance with Regulations 542.1.3.1 and 542.1.3.2. Additionally, there shall be an earth electrode, supplementing any earthing facility provided by the distributor, in accordance with one of the requirements of Regulation 542.2.3, to prevent the appearance of a dangerous touch voltage in the event of the loss of the main connection to Earth.

Hands up all those who think that t'committee simply did not think about the consequences of that and a requirement to ensure that earthing is adequate when there cannot possibly be any definition of "adequate" apart from "complies with {list of all regs imposing requirements for earthing}"?

And ditto all those who think that in Wiring Matters they will publish a piece explaining how the regulations don't actually mean what they can only mean.

 

[bernardgreen]

it will mean for a few years that electrical work will very often have to start by installation of an earth rod.

And on the 13th floor of a tower block this earth rod will be ?

installed in the window box

 

[securespark]

 

[SUNRAY]

And on the 13th floor of a tower block this earth rod will be ?

installed in the window box

Sad to say I've seen that, someone altered their patio and built raised beds, then moved their shared service phone line earth into the said bed.

On a different phone line, customer was complaining their phone didn't work but the dog did knew when it was ringing. Their gas supply was replaced with a plastic pipe and the dog was chained to the internal steel pipe.

 

[ban-all-sheds]

http://msgboard.snopes.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=74;t=001085;p=1

 

[JohnW2]

And on the 13th floor of a tower block this earth rod will be ? installed in the window box

Indeed. That's an issue we've discussed before, and no-one seems to have a clue as to how one is meant to handle such a situation.

The nearest to a sensible solution I can think of would be that the requirement would be to connect an earth rod just to the incoming supply to the building, before it was distributed to the various dwellings within the building - but what it said in the DPC gave no hint about that.

Of course, if Risteard happens to be right, we should have at least a couple more years to think about this, and an opportunity to comment in relation to a further DPC.

Kind Regards, John

 

[ban-all-sheds]

That "solution" is one thing.

Who would pay for it is quite another.

 

[bernardgreen]

and no-one seems to have a clue as to how one is meant to handle such a situation.

One opton would be a ground rod ( at ground level ) and a substantial conductorm a raising earth, ran up to the top of the building.

Each flat then connects it's MET to the rising earth.

Provided the rising earth does not penetrate the equipotential zone of a flat then that is OK. If however the rising earth does penetrate the equipotential zone of a flat then is has to be considered as an extraneous conductor and would therefore need to be bonded to the MET.

One could be forgiven for having two 10mm cables from the MET to the rising earth. One 10 mm would be the Earth cable to the Ground rod bringing the safety Earth into the flat and the other 10 mm cable would be the bonding cable needed to prevent any extraneous voltages entering the equipotential zone of the flat.

Confused, yes, apply common sense and label the cables appropriately

 

[ban-all-sheds]

One opton would be a ground rod ( at ground level ) and a substantial conductorm a raising earth, ran up to the top of the building.

Each flat then connects it's MET to the rising earth.

So who would/should pay for that if it's required because the bloke in Flat 13A has a new CU?

One could be forgiven for having two 10mm cables from the MET to the rising earth.

No, one couldn't, because....

One 10 mm would be the Earth cable to the Ground rod bringing the safety Earth into the flat

That cable would be an extraneous conductive part, as it would be the rising earth penetrating the equipotential zone of a flat.

and the other 10 mm cable would be the bonding cable needed to prevent any extraneous voltages entering the equipotential zone of the flat.

So therefore that bonding cable, like any other, should be connected to the e-c-p (i.e. the first 10mm cable) as near as possible to its point of entry after it enters the equipotential zone.

Confused, yes, apply common sense and label the cables appropriately

Common sense says that the ESQCR should be amended to require the earth rod to be connected to the supply neutral on the network side.

 

[SUNRAY]

http://msgboard.snopes.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=74;t=001085;p=1

I didn't know this has become a 'my friend says'. This was a real situation and took several visits to find as the chain would often be in contact with some other earthed item and test OK. I was called in to make it into a 2 man team (basically to foot the ladder and never actually went inside) to run a wire down from the 2nd floor flat to a new earth rod. In those days an earthed gas or water pipe was permissible for phone signalling if an earth rod was not practicable and the mass introduction of plastic pipes created many telephone faults. Obviously the easiest fix was convert to non shared if copper pairs permitted.