"If"
as the Spartans said.
It is however improbable.
I think they are trying to fob you off.
OOI, my house was built long before 2002, and is PME. It has been common practice around the country for more years than I can remember.
No Main Earth Connection
- Thread starter firapara
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"If"
as the Spartans said.
It is however improbable.
I think they are trying to fob you off.
OOI, my house was built long before 2002, and is PME. It has been common practice around the country for more years than I can remember.
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That makes little/no sense to me. All that is required to convert a non-PME supply to a PME one is for them to add one additional connection from the neutral to an earth rod (most usually, I gather, at the end of the DNO's cable run) - no 're-laying' of cable is required
The 'M' of PME means 'multiple', and I once thought that this always meant that there were several connections from the neutral supply cable to earth along its length. However, we were told by someone who knew (unfortunately no longer with us) that, as above, the 'M' often mean just one additional earthing of the neutral, at the end of the run (in addition to the earthing at the substation) - such that ''multiple' commonly means just two.
Kind Regards, John
True. However, it has always been my understanding that IF the DNO supplies and earth and that earth is used by the consumer, then it is the responsibility of the DNO to maintain a satisfactory earth connection for the installation. Is that not the case?
IF that is true, and IF what we're seeing is a DNO-supplied TN-S earth (like others, I'm not convinced), then they would presumably be responsibly for maintaining a satisfactory earth - either by repairing the TN-S one (unlikely) or (much more likely) converting it to TN-C-S ('PME').
Kind Regards, John
In some cases it could be M = Missing. ( from the 1980's )
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Some of my training with BT included input from DNO, he brought along a sample of cable to demonstrate PME. It had plated copper wires embedded in the outer pvc layer such that they made contact with the mud they're buried in to provide a very long earth electrode.
I came out of BT in 1994.
I came out of BT in 1994.
Interesting, maybe they use such things for 'new cable installs', but I seriously doubt that they would dig up and replace a whole cable to to achieve 'conversion to PME'.
As I said, westie used to tell us that when a TN-S earth failed, a very common DNO practice was to 'convert to PME' simply by adding an earth electrode (to earth the neutral of the existing cable) at the far end of the existing cable run, such that (including the one at the transformer) 'Multiple' = 2.
Kind Regards, John
...incidental earthing.
Indeed. However, increasingly no so, as water/gas supply pipes change to plastic - so one certainly could not 'rely upon' that.
However, don't forget that it was only at the 11th hour that a requirement was removed from BS7671:2018 for every installation (including TN-C-S ones) to have an earth rod. I therefore would not be at all surprised if it rears it's head again in "the 19th", if not an Amendment to "the 18th".
Kind Regards, John
bit tricky if you are the homeowner, and have a 12th-floor flat.
Indeed. I suspect that is amongst the reasons why that new reg got 'pulled', just in time.
Kind Regards, John
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It was always my understanding that the DNO was responsible for providing an earth connection if the supply was TN.
If the supply is TT, they are not responsible.
My personal opinion of that supply cable is that the earth connection looks like an amateur job.
The pipe clamp is not designed for use on cable.
Your supply cable could be TT.
I have seen many a subterranean TT supply. But I think it unlikely in a block.of flats as putting in rods for each flat would be a nightmare.
I would try and get access to other flats to look at their supply cables to see what they are like.
Get photos and then (assuming there is an official DNO earth terminal) you could use them to persuade the DNO to install a proper earth connection.
If the supply is TT, they are not responsible.
My personal opinion of that supply cable is that the earth connection looks like an amateur job.
The pipe clamp is not designed for use on cable.
Your supply cable could be TT.
I have seen many a subterranean TT supply. But I think it unlikely in a block.of flats as putting in rods for each flat would be a nightmare.
I would try and get access to other flats to look at their supply cables to see what they are like.
Get photos and then (assuming there is an official DNO earth terminal) you could use them to persuade the DNO to install a proper earth connection.
Is that not inevitable since, doesn't "the supply is TN" means that they are providing (or, at least, 'offering') an earth?
As I've said, it's always been my understanding (not necessarily correct
) that once a DNO has 'provided' an earth, they have an obligation to maintain an adequate earth, even if that means changing a ('failed') TN-S earth to a TN-C-S one.Again, I think that is an inevitable truth, since DNOs do not (to the best of my knowledge) provide TT earths. They do provide supplies consisting of just L and N (like I have), but it's then down to the customer to provide an earth (which obviously has to be TT).
What do you mean by that? Are you, as above, talking about a supply which is just L and N (like mine)?
Kind Regards, John
when I had a house with a 1920's supply cable in outer London, looking like the OP's, there was a wound-on steel "bandage" armour (which went rusty in the ground, might originally have had bituminous paint), and a bituminous cloth bandage, inside which was a lead sheath with two conductors (I have an idea they might have been wax-paper insulated).
An electrician had previously incorrectly put a pipe clamp on the armour, but when a new meter was fitted, the iron service-head was replaced with modern grey plastic, the fitter stripped back the armour and put an earth clip on the lead sheath. I had an idea they would change it to PME, but I don't think they did. I wrote and asked if they would, and they said yes, but only if I had an EICR done first.
I think the iron head originally provided some kind of earth as it must have clamped the steel armour and the lead sheath.
An electrician had previously incorrectly put a pipe clamp on the armour, but when a new meter was fitted, the iron service-head was replaced with modern grey plastic, the fitter stripped back the armour and put an earth clip on the lead sheath. I had an idea they would change it to PME, but I don't think they did. I wrote and asked if they would, and they said yes, but only if I had an EICR done first.
I think the iron head originally provided some kind of earth as it must have clamped the steel armour and the lead sheath.
That's an interesting one. Did they give any indication (or did you have any thoughts/theories) as to why they wanted an EICR?
Kind Regards, John
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