Tn-c-s pme

[West Kernow Ele]

Visited a house last week to correct a supplier fitted RCD in the tails that they had wired incorrectly. Supply tails on wrong side of RCD. Current supply is TT but post in garden indicates that PME supply is available. Place needs a 17th board and total rewire which will be done in Nov but meter needs moving for builders to remove wall 1st.
I suggested that when they have meter moved that they request upgrade to the PME supply (the TT rod is burried under a concrete path and has a relatively high ohms reading).
They have been told by supply company (SWEB) that they cannot have PME as they have an overhead supply from the post, even though the post is marked PME and all supplies from it are overhead. They went on to say I was passing the buck as I should fit the PME earth conductor to their kit!!!!!!:dozey:

Question has anyone come accross issues with having PME supply on overhead cables?? Or been told to access the Supply companies kit to do it themselves.

Tom

 

[Knobhead]

To be honest get a new stake in and ignore the DNO’s suggestion. Regard it as TT.

If anything goes wrong they’ll be the first pointing the finger. Unless of course you have it in writing from them, then slap a bill in to them for up grading their system.

Oh look, there’s a flying pink pig!

It may be PME up to the pole in the garden, but the DNO can’t guarantee the last section to the house!

 

[Engineer54]

Most of the Original DNO PME supplies were ''All Overhead supplies''. All these supplies were originally TT. PME supplies were the old electricity boards answer to supplying a Low cost (compared to supplying a TN-S earth) good maintainable earth connection for these suburban and semi rural domestic/commercial and small industrial installations.
We all know that these day's the DNO are in the process of converting all DNO supplies to PME, even the existing TN-S supplies....


This DNO company is talking out of there arse, if the overhead neutral conductor is a PME Neutral, then it will remain so at the cut out. In fact it's already a PME'd neutral, it only needs a suitable cut-out to combine the installations main earth conductor. I would advise the homeowner to take this further with the DNO company!!!

 

[Knobhead]

So am I wrong in what I said?

 

[Engineer54]

If there was no other alternative, i'd totally agree with you, but i don't like to see TT on domestics, and will always go with getting a DNO earthing system if and whenever possible.

I'm going by what was written in the OP, where the DNO came out with a ridiculous statement, and then told the poster to make the connection themselves.

As the connection to the property is also overhead, and no mention has been made as to the house being at the very end of the string, i can't see any problem for them NOT making the PME connection, can you??

 

[Jimmyb]

i had same problem, i test it and found a ze value of 0.48 so put it down to that

 

[Engineer54]

You've lost me there Jimmy, What Problem, what did you test and put what down to that ???

 

[Richard Burns]

I have just done work on a house with an overhead PME supply and my Ze was a little high (0.42ohm) DNO (actually EDF) came out and tightened the connections and all OK. But he did say that if there was a more significant problem they would drop another earth point down from the last pole (about 20m away) to sort it out.
So it is possible and relatively cheap for them to fix (so long as the rest of the supply is OK).

However the DNO will not sort it out, as they say, then I would go with Tony's suggestion
To be honest get a new stake in and ignore the DNO’s suggestion. Regard it as TT.

If anything goes wrong they’ll be the first pointing the finger. Unless of course you have it in writing from them, then slap a bill in to them for up grading their system.

 

[platty1005]

If the pole says PME system then that is the system from the local transformer and is the DNO's responsibility to comply with the ESQCR. Ring back and threaten to report them. Ring NICEIC helpline for more advice in my opinion they are talking B*****s and it is their LEGAL responsibility to put it right so get tough an don't take any s***!!

 

[netblindpaul]

OK the DNO has a statute law responsibility to maintain the earth IF they supply it.
Else they do not.
They are allowed not to supply one and they unfortunately can withdraw it at any time with the notice required under statute law.
Just PME it yourself, but DO NOT CONNECT the PME at the head yourself, as this would be a statute law offence.
Drop a rod at the origin and any other DB's, with earthing conductors sized at S or above and any other convenient points.

I also prefer the DNO earth as it is rare that TT earths on domestics are correctly installed.

 

[Engineer54]

OK the DNO has a statute law responsibility to maintain the earth IF they supply it.
Else they do not.
They are allowed not to supply one and they unfortunately can withdraw it at any time with the notice required under statute law.
Just PME it yourself, but DO NOT CONNECT the PME at the head yourself, as this would be a statute law offence.
Drop a rod at the origin and any other DB's, with earthing conductors sized at S or above and any other convenient points.

I also prefer the DNO earth as it is rare that TT earths on domestics are correctly installed.

Now you really have surprised me ...lol!!! I would have thought you the last person to suggest such a connection.

So where are you suggesting the Neutral/Earth link to be, ...in the CU between the the N-E bars??

 

[netblindpaul]

Eng,
I'm NOT suggesting connecting it at the head as my sentence goes on to say.

P-Protective
M-Multiple
E-Earthing

The clue is in the M!

Nothing to do with TN-C-S

I am suggesting that you fit MULTIPLE earthing points thought the consumers side distribution.

What ever you do you must NEVER tamper with or change before the meter.

 

[malcolmsanford]

To be honest Paul I think like E54 I was thinking you were advocating a proper PME within the installation which you know is not on as per the ESQCR.

You are right in that there is nothing wrong and in many cases advantages to tieing earth rods together throughout an installation but as like E54 I was taking your PME as the literal using a combined PEN conductor inside the installation.

 

[netblindpaul]

OK guys sorry for the confusion.
I tend to treat TN-C-S & PME as 2 separate issues.

 

[Engineer54]

Eng,
I'm NOT suggesting connecting it at the head as my sentence goes on to say.

P-Protective
M-Multiple
E-Earthing

The clue is in the M!

Nothing to do with TN-C-S

I am suggesting that you fit MULTIPLE earthing points thought the consumers side distribution.

What ever you do you must NEVER tamper with or change before the meter.

You certainly confused me!! ...lol!!

The fact is, there is a bona fide PEN conductor sitting at the cut-out in this instance. All it requires is the DNO to install a link between that PEN conductor and the MET, what objection can they have to complying with this request?? I can't think of a single one, which is why i advised the author of the OP to get the home owners to take the matter further. Let's face it, the excuse they gave was to say the least absurd, especially when suggesting the electrician should make the CNE connection himself!!