DNO's responsibility for TNCS

[riveralt]

I am doing a house rewire at the moment. The old set up included a TT earthing system. Though a visual check at the main fuse suggested that it may also have been updated to a PME system at some stage in the past.

Scottish Power have now been out, checked and confirmed that a PME system is fitted to these premises.

Scottish Power are stating that there is nothing more for them to do.

The problem I have is that there is no earthing cable running from the incoming head to the main earthing terminal.

Who is responsible for running the earthing cable from the pme head to the main earthing terminal?

 

[safesinbad]

not you thats for sure, unless you want scottish power to bitch about you cutting the seals lol

 

[STI]

Am i missing something here , if the Earth cable is missing how could it be confirmed it is a PME.

 

[skenk]

Does anyone have any actual evidence that Scottish Power have ever taken action against an electrician who has cut a seal on a cutout?

 

[safesinbad]

Am i missing something here , if the Earth cable is missing how could it be confirmed it is a PME.

Just test the Ze between live and neutral if its a 2wire supply

 

[STI]

Safesinbad, thanks that makes sense but wouldnt it still be possible with a reading of less than 0.35 to be a TNs or TT. If there is no earth wire present. I accept less likely but possible?

 

[LoveRocket]

Am i missing something here , if the Earth cable is missing how could it be confirmed it is a PME.

Just test the Ze between live and neutral if its a 2wire supply

I think you mean test the Ze between the Phase and Earth terminals directly on the head - by means of shoving a probe in the earth hole!

Testing between Phase and Neutral tells you nothing about Ze. At all. Ever.

So if you did as you say on this installation and got 0.2ohms, would you say all is fine and dandy despite there being no bloody main earth conductor?

Remove that thanks, STI!

 

[Steve]

In answer to the original question, many PME cutouts have an accessible earth terminal. But many do not. If he needs to, your electrician might cut the seals. The DNO wont connect an earth wire to their terminal if you dont have one ready for them. Similarly, metering guys wont connect tails to the meter if you dont have any ready for it. Because that'd just be stupid anyway, but similar scenario.

 

[safesinbad]

Am i missing something here , if the Earth cable is missing how could it be confirmed it is a PME.

Just test the Ze between live and neutral if its a 2wire supply

I think you mean test the Ze between the Phase and Earth terminals directly on the head - by means of shoving a probe in the earth hole!

Testing between Phase and Neutral tells you nothing about Ze. At all. Ever.

So if you did as you say on this installation and got 0.2ohms, would you say all is fine and dandy despite there being no bloody main earth conductor?

Remove that thanks, STI!

yes i would. If you took some time to read the first post then read what i posted why wouldn't it be fine and dandy as you like to put it. You're here to advise, not to be a smart ass

 

[LoveRocket]

Because doing what you say would show nothing other than show that there's continuity between phase and neutral. It shows nothing of the earthing arrangement.

You could be on the end of several miles of supply cable, with the only earth rod being back at the distro transformer. That is not PME.

It is only a TN-C-S supply if ti's specefied for it, the DNO say it is, and install a suitable service head.

Do you really think that continuity between P&N = a perfectly acceptable earth?

Please tell me you're not a professional electrician?

 

[STI]

OOps just got back from eating. I wont remove my thanks from safesinbad as i didnt read the post properly and i now see the mistake about phase and neutral. When i first read it i just thought the answer was tke the Ze reading. I can understand the principle of and thanks for the guidance (so half a thanks at least)but i still come back to, if there is no earth wire present and as Loverocket says if my reading is 0.2 have i proved its a TNCS or could it still be a bl**dy good reading from a TT or TNS however unlikely. Or is there something else that could be done to confirm its a TNCS

 

[safesinbad]

no i am not saying that testing between p&n is an acceptable earth but what i am saying is testing between p&n for earth after scottish power have confirmed that it is a pme confirms that there is pme, i aint sayin that i would go into the cut out myself but the evidence is there that there is earth wouldn't you agree.

 

[LoveRocket]

no i am not saying that testing between p&n is an acceptable earth but what i am saying is testing between p&n for earth after scottish power have confirmed that it is a pme confirms that there is pme, i aint sayin that i would go into the cut out myself but the evidence is there that there is earth wouldn't you agree.

What are you saying?

What do you mean "Testing between P&N for earth"? That makes no sense.

 

[electronicsuk]

no i am not saying that testing between p&n is an acceptable earth but what i am saying is testing between p&n for earth after scottish power have confirmed that it is a pme confirms that there is pme, i aint sayin that i would go into the cut out myself but the evidence is there that there is earth wouldn't you agree.

What are you saying?

What do you mean "Testing between P&N for earth"? That makes no sense.

Agreed. Safesinbad, I think you might just have to grit your teeth on this one and stop digging any further, as what you've said so far is pretty much, to put it nicely, a load of rubbish. That is, apart from the bit about the DNO visiting and confirming the earthing arrangements. If they say that PME is provided at the property after a site visit, then that should be the case.

Whether it's right or not, the spark would usually make the main earth connections to the cutout. As Steve mentioned, this is sometimes possible without removing the fuse and earth terminal cover.

 

[safesinbad]

ok. when your testing your Ze you test between p&e right. Inside the cut-out there is a neutral block and also an earth block. These two blocks are connected together by use of a copper bar. I've checked google for images but can't seem to find any. This is what i mean by testing to neutral. Your neutral is your earth on a pme system