Earth supply by dno

[bengasman]

Does the DNO come out to install an earth supply for TNS system if there is no earth at all?
I stumbled upon a situation where the whole house seemed to be a bit outdated in terms of utilities and it looks like one of those places where the earth is still supplied by the lead water mains.
No sign of a proper earth connection anywhere near the cutout nor near the CU.
Incoming supply is a clearly visible tar coated cable and no chance of anything ever having been taken from there.
Croydon postcode; who is DNO there these days?
Number to call would be most appreciated, as is an opinion about their common attitude to this situation with respect to timeframe and cost.

Thanks folks.

 

[plugwash]

IIRC DNOs are not required to supply an earth but are required to maintain it if one has been previously supplied.

 

[JohnW2]

Does the DNO come out to install an earth supply for TNS system if there is no earth at all? ... Incoming supply is a clearly visible tar coated cable and no chance of anything ever having been taken from there.

It sounds as if you are describing TT, not TN-S - i.e. the DNO has never supplied an earth connection, with the expectation that the consumer will provide their own TT electrode (rod).

As plugwash has indicated, it is generally said that DNOs are under no obligation to provide an earth, but do have to maintain an earthg they have previously supplied (although it's not clear that all DNOs actually work to this 'rule'). However, even by that rule, if they have never provided an earth, they would be under no obligation to provide one now.

Kind Regards, John

 

[JohnD]

if asked, they will often provide one for a fee. I have an idea EDF used to quote £150 in London, which I think is worth it.

Some might even do it for nothing if you are very lucky.

It is important to provide a good main earth conductor beforehand, preferably 16mm going to your own earth block, and long enough to reach the cutout, otherwise they are liable to connect to the thin bit of bare copper often found in old installations. Am 8-way block is very inexpensive and can become your MET and have services such as gas and water connected to it, as well as the 16mm to the CU(s)

An MET is one of the few things you are permitted to fix to meter board, if necessary.

You can often get PME now, even in rural locations with an overhead supply.

You aren't expected to know your DNO, if you contact your electricity supplier (preferably by short letter) they are supposed to pass it along until it reaches someone who knows what they are doing. Phone calls are often fobbed off.

http://www.nationalgrid.com/uk/Electricity/AboutElectricity/DistributionCompanies/

 

[bengasman]

Does the DNO come out to install an earth supply for TNS system if there is no earth at all? ... Incoming supply is a clearly visible tar coated cable and no chance of anything ever having been taken from there.

It sounds as if you are describing TT, not TN-S ...

Defintely not TT, there is no 100 mA rcd; this is in a fully build up area where everybody has DNO supplied earth. Owner has lived there 40 years and leccie never been upgraded from the days earth was taken from the lead watermains.

 

[sparkybird]

EDF (as was) will never provide a 'free' earth. If you can get them to strap onto the lead sheath expect to pay at least £250 + VAT.

An earth rod might be an easier (or the only) option, but then you'd be looking a board upgrade.....


Good luck!

 

[westie101]

I suspect the o/p is suggesting that he wants a TN-S earth installed as it is no doubt a PILSTA service cable, asking for a TNC-S would be pointless

 

[AdrianUK]

Defintely not TT, there is no 100 mA rcd; this is in a fully build up area where everybody has DNO supplied earth. Owner has lived there 40 years and leccie never been upgraded from the days earth was taken from the lead watermains.

Think you have your answer there, Ben..... 40 odd years ago we didnt really have RCD's ... so a "true" TT installation using the watermain would have been the norm..... and it would probabley have been OK, miles & miles of lead water pipe buried in the ground would have made a decent electrode with a low enough impedance that the fault current would be big enough to open the rewireable fuse.

 

[JohnW2]

It sounds as if you are describing TT, not TN-S ...

Defintely not TT, there is no 100 mA rcd; this is in a fully build up area where everybody has DNO supplied earth.

Maybe the others have all been upgraded? You said "Incoming supply is a clearly visible tar coated cable and no chance of anything ever having been taken from there.", which is close to saying that it has never been TN-S. The fact that no-one has ever installed an RCD (even if they should have) obviously doesn't prove it's not TT. Furthermore, you imply that nothing has been done to the installation in the last 40 years, and I'm not atr all sure that RCDs even existed 40 years ago.

Owner has lived there 40 years and leccie never been upgraded from the days earth was taken from the lead watermains.

'Earth taken from watermains' (rather than provided by DNO) is TT. If it's never been unpgraded in 40 years, then it's presumably still TT.

Kind Regards, John

 

[westie101]

Report it to their emergency line one morning as a smell of burning/crackling noise or something similar.
If lucky the jointer will probably change the cut-out & fit an earth as no doubt their CoP will require it

Just don't mention earthing to the call centre!!

 

[bengasman]

Probably poor choice of words on my side. What I meant by "not TT" was no spike or anything like that.
I'll bring my tester next time I go over and see what sort of reading I get for pfc.
Thanks guys.

 

[JohnW2]

Probably poor choice of words on my side. What I meant by "not TT" was no spike or anything like that.

Fair enough. It sounds like good old-fashioned ('water pipe') TT - which obviously should now have a dedicated electrode/rod/spike, since it is no longer acceoptable to rely on supply pipes. Whether or not the DNO would be able/prepared to upgrade it to TN (TN-S or TN-C-S) and for what (if any) cost appears to depend upon such factors as which DNO they are and which side of the bed they got out of on the day in question!!

I'll bring my tester next time I go over and see what sort of reading I get for pfc.

Unless the installation is lucky enough to be 'enjoying' an indirect TN earth connection from a neighbour via the pipework, you'll almost cefrtainly not get Zs figures low enough to achieve required disconnection times (even if/when a TT rod is fitted) - so the installation is likely to need everything to be RCD protected unless you can get the earth upgraded to TN.

Kind Regards,John

 

[westie101]

Or, as a lot do get the customer to ring & just report a high ZE.
It is likely the water supply will now be plastic so the ZE will be very high. In theory the Water Company should, note that word should, have ensured it was OK after changing the water service - they never have done in my experience! They should also pay any costs involved - fat chance!

 

[bengasman]

We shall see what testing shows and what the DNO offers. Personally, I don't like TT systems of any form. Nice TNCS with big earth connections and very low Z values that click out the breakers without fail, is what I like.

Not all is lost thouch as the lead mains is still there and will stay there until it is compulsory to replace. Even better, various underground little streams help to keep ground damp all year long even during sever drought. Maybe addition of long spike hammered into the center of one of the damp spots can help things for the time being. Only cost a couple of quid and takes 5 minutes.

 

[bengasman]

...Water Company should, note that word should...

Indeed. Water company around here can't even fix a water leak, let alone look at anything else.
When I moved in, they were repairing leaks at more or less the same spot as where they now blocked off half the road AGAIN . 5 years of messing about, and it's still not sorted.