High earth reading

[ebee]

I have seen many a TN system in a neighbouring "Board area" where the sheath was clamped with a buckle type thingy and frankly I would prefer a Temby earth clamp as superior, they were quite common years ago .
Of course, nothing beats a good old sweat joint roviding the earthwire is more substantial than a bit of thin fusewire.

 

[Guitarguy]

Does that not imply that the DNO didn't do it (and therefore may not have "provided an earth")?

Most probably, someone has ‘helped themselves’

 

[Jurassicspark]

the 'bet' presumably needs to be on what sort of installation the DNO regard it as being, doesn't it?

And that can be easily identified.

Don't you agree?

 

[JohnW2]

And that can be easily identified. Don't you agree?

Well, I agree that, in simplistic terms, it 'looks like' TN-S - but, as I just wrote, it also seems likely thst at least the present connection to the cable sheath (be it the right cable or not!), and maybe the only connection to the cable sheath, was installed by someone other than the DNO - in which case (given that it's certainly not TN-C-S), that would presumably wouldmean that the DNO regard it as TT.

If yoy believe that the type of 'earth' (in the eyes of the DNO) can be "easily identified", perhaps you could explain your thinking? Thanks.

 

[JohnW2]

Most probably, someone has ‘helped themselves’

Exactly, and if (as is possible) the DNO has never 'provided an earth', then they presumably regard it as a TT instalation, hence with no responsibility on their part to 'maintain the earth'??

 

[Guitarguy]

That’s right, and also years ago the earth was provided by lead water mains and since those have mostly been replaced with plastic, many houses are left with no earth

 

[JohnW2]

That’s right, and also years ago the earth was provided by lead water mains and since those have mostly been replaced with plastic, many houses are left with no earth

Indeed - and those installations presumably were always regarded by DNOs as TT ?

 

[Jurassicspark]

If yoy believe that the type of 'earth' (in the eyes of the DNO) can be "easily identified", perhaps you could explain your thinking? Thanks.

If it has been fed with a split concentric cable then it will be TNS. Next door supply needs checking if that is a TNS or even TNCS then the chances of that individual installation being TT is rare.

 

[JohnW2]

If it has been fed with a split concentric cable then it will be TNS.

Do we know that it's split con?

Next door supply needs checking if that is a TNS or even TNCS then the chances of that individual installation being TT is rare.

If the next door supply is TN-S or TN-C-S, then the OP's certainly wouldn't need to be TT - but there are a good few "ifs" in all that

 

[Jurassicspark]

Do we know that it's split con?

No, but the DNO will be able to know if it is.

If the next door supply is TN-S or TN-C-S, then the OP's certainly wouldn't need to be TT - but there are a good few "ifs" in all that

Mhm, not impossible though.

 

[Jurassicspark]

That’s right, and also years ago the earth was provided by lead water mains and since those have mostly been replaced with plastic, many houses are left with no earth

If the pipe is made redundant and doesn't serve a purpose and has an acceptable ze value then it can be used as the main earth. It is much feasible than banging several rods in the ground too.

 

[JohnW2]

If the pipe is made redundant and doesn't serve a purpose and has an acceptable ze value then it can be used as the main earth.

Yes, but isn't that a fairly big IF? - since it's not uncommon when metal water supply pipes are changed to plastic for little, if any, underground metal pipe to remain (electrically) connected to any pipes within the building (if, indeed, a metal pipe entering the building still exists)?

 

[JohnW2]

No, but the DNO will be able to know if it is.

One would hope so- but isn't it tooold to be split con?

Mhm, not impossible though.

Little in this world is totally impossible

 

[ebee]

The DNO will/should have declared it but in real life might want to take a look themselves before declaring..

Yo might take the view that a self declaring DNO might, at times, not be fair but what , if anything, in life is ?
Where I live the majority were TNS and would have been declared so but in the past few years so many repairs near and far have rendered to be more than a bit TNC-S like in many ways tgat TNC- S is probably the defacto they would declare in most instances , TT is fairly rare except if someone splits off from their own TN system to make a TT island nearby..
In fact tge DNO always insisted that if we did a temporary supply to allow work to commence after a disconnection tgat we had an Earth rod and RCD before they would connect for for building works to proceed as the incomming earth connection could not be relied upon until works completed and they had actually tested their own TN network nearby that installation on completion.

 

[pete01]

Right.

Regarding the connection, it should be either a sweated connection or constant force spring.

A lot of people say it's a C2 and a call to the DNO, so I'm sure they might/can do something? No one wants to see a situation of a shorted incomer.

I agree those clamps are made for pipes not cables.