The DNO and supplying an earth

[studentspark]

Would appreciate some thoughts on this situation.

Customer has a high Ze reading 720 ohms

The supply cable is the two core lead sheath type.

The earth connection is a BS 951 clamp onto the lead, off to the met.

Now, the person who fitted this clamp managed to clamp it on to the heat shrink and not the lead, hence the poor reading. Looks like it has been like that for many a year. (The fact that a new CU had been fitted, and this not picked up is another matter)

A reading to the lead sheath gives a good reading, but poor from the clamp.

I contacted the DNO, who called and said its not their problem, as they did not fit it.

The only solution is to TT it or pay them to convert to TN-CS.

I think thats a bit harsh on the home owner.

How do we know they did not fit the clamp - I have read of plenty of posts where DNO types have said they used these clamps in the distant past.

So if they supplied it they have a duty to maintain it.


The DNO chap said I should just put another clamp on the cable !

I am not happy screwing a clamp onto an old lead cable, so thats not happening

Do the DNO still attach an earthing conductors to lead sheath?

So if the DNO keep the stance that its nothing to do with them, what about the fact that this is exposed earthed metal coming into a property, so surly this needs to be connected to the MET.
An electrician can't do that. We keep being told we can't touch their stuff- and I don't want to anyway.

If I TT it you could have two different earths ?


Appreciate thoughts
Thanks

 

[ericmark]

The DNO bit can't really answer but multiple earth's is an easy one. I heard it said many times in college that you can't have an earth electrode with a TN-C-S supply which is correct but the only reason that's correct is the earth rod becomes an extraneous-conductive-part all it does is change name.

So there is no reason for not fitting an earth rod and bonding it to the house earth it's only the name that changes be it a circuit protective conductors or a main protective bonding conductors or an earthing conductors it's only the name which changes.

In the past my son found the hard way with DNO you ask them rather than tell them anything. Ask the DNO what is the earthing arrangement on this house and often they don't know so they send a guy to find out. You inform him all the other properties adjoining are TN-C-S and likely he will make that property also TN-C-S. But tell them that their earth is faulty and straight away you risk putting them into defensive mode.

 

[JohnW2]

How do we know they did not fit the clamp - I have read of plenty of posts where DNO types have said they used these clamps in the distant past. ... So if they supplied it they have a duty to maintain it.

Yes, that's what we're always being told. Don't they keep records of whether or not they are providing an earth and, if so, whether it's TN-S or TN-C-S?

The DNO chap said I should just put another clamp on the cable !

Hmmm - I bet you wouldn't be able to get him to say that in writing!

I am not happy screwing a clamp onto an old lead cable, so thats not happening

I don't blame you!

So if the DNO keep the stance that its nothing to do with them, what about the fact that this is exposed earthed metal coming into a property, so surly this needs to be connected to the MET. ... An electrician can't do that. We keep being told we can't touch their stuff- and I don't want to anyway.

That's a very good point. As you say, if you TTd the installation, if there is an exposed sheath of the incoming cable, that would constitute an extraneous-c-p which would need to be main bonded to the MET - and, as you say, you are neither 'allowed' to, nor would want to, do that!

I'll be interested to hear a DNO's perspective on this one - westie??

Kind Regards, John

 

[JohnW2]

So there is no reason for not fitting an earth rod and bonding it to the house earth it's only the name that changes be it a circuit protective conductors or a main protective bonding conductors or an earthing conductors it's only the name which changes.

That's all true - but, in the OP's case, he does not have a satisfactory connection to the incoming cable sheath. That connection is required, whether one calls it an earthing conductor or a main bonding conductor and, not unreasonably, the OP doesn't want to play at clamping something onto the DNO's incoming cable (of unknown condition).

Kind Regards, John

 

[RF Lighting]

Just get a constant force spring and clamp an earth to the sheath with that.

 

[studentspark]

Constant force springs.

Never heard of them, will have a look

Thanks

 

[JohnW2]

Just get a constant force spring and clamp an earth to the sheath with that.

There's presumably still a need to 'clean up' the sheath before applying the clamp, and I'm not sure I would want to be doing that, particularly upstream of the service fuse on a supply cable of 'unknown condition' - or am I just over-cautious (or a coward!)?

Kind Regards, John

 

[studentspark]

OK.

If I used these, what's the legal situation. I think I would be in choppy water should any issue arise, for as I understand it , I can't touch DNO equipment.

 

[westie101]

I contacted the DNO, who called and said its not their problem, as they did not fit it.

I doubt that any DNO employee would fit one in that position

The only solution is to TT it or pay them to convert to TN-CS.

Why TNCS? Why not TNS which would be much easier for the DNO to supply as an earth.
Depending on DNO they may have to do like us do the neutral earth bond in a new joint on the main and install a whole new service as we cannot just bond the neutral to earth at the cut-out of a lead sheath service.
Which as you can guess is not a cheap job
To do such a bond we would class as unsafe as the size of the bond would
be far less that the size of the live & neutral conductors in the main

I really wonder what the fascination with TNCS is, it is no better or safer than TNS.

I think thats a bit harsh on the home owner.

Talk to the relevant government department as that is what ESQCR says, sad to sat that DNOs are not charities, perhaps if they were to supply an earth free you would not charge your customer for the work!

the fact that this is exposed earthed metal coming into a property, so surly this needs to be connected to the MET

So insulate it with a suitable tape or piece of split plastic pipe that it isn't exposed

 

[EFLImpudence]

I contacted the DNO, who called and said its not their problem, as they did not fit it.

I doubt that any DNO employee would fit one in that position

Are you saying the lead sheath is not nor ever has been the earthing method?

Perhaps someone else had to fit it the last time the DNO refused to repair their earth connection.

 

[westie101]

Are you saying the lead sheath is not nor ever has been the earthing method?

That is quite likely, we come across this situation once or twice a week. Generally it goes back to metallic gas and water pipes being used as the earth in times gone by but that method no longer applies.
We tend to find this more in supplies installed prior to the nationalization of the supply industry (1947)

 

[studentspark]

Humm.

I think Ericmark hit the nail on the head.

To Westie..

I don't think the DNO is a charity at all , you levy a charge on every customer.

But I don't want an argument between (us and them).

This is a genuine question..

I just don't get the fundamental idea that you do not have to provide an earth. (But you do in most domestic situations it seems)

Practically all the houses I have worked on, the majority being TNS have a earth lead off the cable.

For some reason this house does not have one, I don't know why.

Why would they have left it with no provision to provide an earth ?

Why do you not have to provide an earth?

Thanks

 

[JohnW2]

I really wonder what the fascination with TNCS is, it is no better or safer than TNS.

I haven't really noticed any 'fascination', particularly not here. There are at least a few people here you repeatedly express their concerns about TN-C-S, suggesting that it is only done as a 'cost-cutting' exercise!

So insulate it with a suitable tape or piece of split plastic pipe that it isn't exposed

Oooh. Logical though that might sound, I've never seen that suggested, least of all in BS7671, as an acceptable alternative to main bonding an extraneous-c-p! The rules about main bonding seem to be concerned about the possibility that someone might creep in one dark night and slip a bit of plastic pipe into what was previously a continuous metal pipe run, so I might have expected them to be equally concerned about possible future removal of your 'tape or piece of split plastic pipe'!

Kind Regards, John

 

[westie101]

Why do you not have to provide an earth?

Why ESQCR was written that way I don;t know and it causes all sorts of issues as you can see.

There are ways round it like reporting a faulty cut-out (but they have to be faulty) and hoping that the jointer supplies an earth as a matter of course.
or
As suggested fit your own using a constant pressure (roll) spring.
As long as there are no signs of cracking on the lead sheath there isn't really an issue, to clean it just needs a gentle rub over with some wet & dry, No files or stuff like that.

As for keeping a record that was always a no way. Think of the space in pre-computer days to keep records of each ser4vice on paper, the patch I cob=ver has about 10,000 customers, but think or the number of customers in a medium of large city,

In terms of reality cut-outs with fused neutrals were outlawed in the 1930s. We are still finding and changing them!

 

[EFLImpudence]

As for keeping a record that was always a no way. Think of the space in pre-computer days to keep records of each ser4vice on paper, the patch I cob=ver has about 10,000 customers, but think or the number of customers in a medium of large city,

They seemed to manage it regarding bills.