BS951 Bonding Clamp on the Incoming Supply

[Marcus Vaughan]

Hi all,

Just been to look at a job for a consumer unit changeout, checked the supply and,


Not sure you can see it too well but TNS system with older earthing conductor in green kind of sweated onto intake (connection does not feel too good), but disconnected at the other end (goes into that little 2 terminal connector block).

A BS951 earthing clamp has been put around the incomer and connected in up to the MET on the top left. Ye-hah!

New consumer unit and presumably this, erm, earthing arrangement installed relatively recently in 2009. 25mm tails, 16mm earth, dual rcd etc.

I measured Ze as is and got 0.12 ohms.
Then as an experiment jumped the 16mm main earthing conductor over onto that little 2 terminal block to measure the original Ze - and got 0.41 ohms. Quite a bit of difference, and I suppose might make a couple of circuits non-compliant. There is a bit of insulation stripped from the old green conductor but I can't see how that is relevant?

What to do though?

It's the 2nd example of this I've seen this month, on the first one I contacted my scheme provider and they said that needs sorting first, so I should contact the DNO, but they are under no obligation to supply or repair the earthing. He even mentioned 'earth rod'.

Leave as it?
Reinstate as before the alteration?
Would DNO be interested?

I'd welcome your thoughts - as I say - I keep coming across this.

Cheers.

 

[ChrisElectrical88]

Come across it a few times, phonef DNO as emergency as earth not satisfactory to the house, attending enginner has always noted the earth needs redoing on their side.

 

[Bobster]

If the DNO has provided an earth. They must maintain it.

Which they clearly have if one is sweated onto the sheath.

 

[Strima]

I would get the DNO to inspect, that clamp could well have caused unseen crush damage to the incoming cable which may well go with a bang if disturbed.

 

[ipf]

Looks like whoever was working on it wasn't happy with that original connection and have made an improvement of their own. Their may have been some damage at sweating point, strands damaged, maybe......really that's down to DNO. It's theirs and they should have been called.
Although there's a better reading, the earth clamp connection could well deteriorate and isn't a correct termination to the lead. Contact them to cover yourself.....I'd say.

 

[Marcus Vaughan]

Thanks all.

Good advice I’m sure.

I’m not sure if I’ve won this work yet, so I might now be able to update.

The house is empty and being refurbished - so I’ll send an e-mail through to the developers and tell them who to call.....

 

[Charlie_]

I’ve seen loads of those clamps on dno incomers.
They usually have a ferrule on the inside so the clamp tightens around that and not against the cores

 

[Deleted member 26818]

At least it’s not a Jubilee clip.

 

[Lucien Nunes]

They usually have a ferrule on the inside so the clamp tightens around that and not against the cores

Which is OK when done correctly, but this might be on the lead which isn't. Actually, yes, Marcus, is it on the lead or the armour? Not actually important if the DNO are going to come and fix it which they should.

I guess younger sparks especially have never handled lead either as cable or in general and aren't aware how easy it is for something sharp like the heel of a clamp to dig a hole through a PILC once the armour is removed. In pipe organs, we always have to tell visitors never to touch or hang on to anything metal, only wood. If sombody loses their footing and grabs hold of a lead-alloy pipe it can just rip apart in their hands.

 

[Marcus Vaughan]

Which is OK when done correctly, but this might be on the lead which isn't. Actually, yes, Marcus, is it on the lead or the armour? Not actually important if the DNO are going to come and fix it which they should.

I guess younger sparks especially have never handled lead either as cable or in general and aren't aware how easy it is for something sharp like the heel of a clamp to dig a hole through a PILC once the armour is removed. In pipe organs, we always have to tell visitors never to touch or hang on to anything metal, only wood. If sombody loses their footing and grabs hold of a lead-alloy pipe it can just rip apart in their hands.

It’s on the lead.