Earth clamp on incoming cable

securespark · 30 Nov 2021

They would have fitted a constant pressure spring to the lead sheath of the incoming cable. The pipe clamp you have is dangerous because it can crush the cable and cause a short circuit.

The spark should have known what the protocol was and shouldn't have bodged it.

If I come across that situation, I would call the DNO to report a dangerous situation, explain what it is and then within 2 hours, they would be there to sort it.

The only proviso is that the DNO will often only maintain an earth connection if there was one existing already. If you have never had an earth connection to the incoming cable, the DNO may refuse to fit one.

I must say that I am assuming he fitted a pipe clamp, but I may be wrong.

Please take a photo of what he did and post it here for us to see.

Harry Bloomfield · 30 Nov 2021

Thank you Securespark - that is the absolutely correct answer.

Harry Bloomfield · 30 Nov 2021

Vicario said:
But my EICR now says that my installation is satisfactory. (Same guy who fitted the new earth). So what is the 'correct way' Harry? How would the DNO have done it differently?

So the guy who did the botch, checked the work he had just done and passed it as satisfactory? What do you think would be the likelihood of him failing his own work?

333rocky333 · 30 Nov 2021

Vicario said:
How would the DNO have done it differently?

Proberly with a "roll spring"

The-earth-wire-is-cut-to-1.5-times-the-length-of-the-removed-section-of-the-outer-protective-coating.jpg

Vicario · 1 Dec 2021

Thanks everyone for the useful answers and pictures. Rocky...I can't find those rings you mention, can you send me a link to where I can buy one? (thanks). I have been reading up about this issue and apparently using this type of clamp to provide an earth is very common and even used by some DNOs. One electrician did query it and reported it to the DNO who said that if he got good readings they weren't bothered. Previously I had no earth and now I do, but clearly you guys are concerned so I won't ignore your advice. UKPN are coming in the New Year to do a site visit about a fuse upgrade so I'll ask them what they think. If I get a ring clamp do you think they'd fit it for me?

333rocky333 · 2 Dec 2021

I have never seen them for sale as singles , only in jointing kits, I would leave the clamp personally till your visit, you provided no pictures so the cable type is not known, i believe the issue with your clamp type is when used on swa, as the inner sheath is soft they do not work as good, when swa cables new a metal sleeve can be slid over first then the armour is clamped between the clamp and that sleeve thus getting maximum pressure similar to when clamping onto a copper water pipe.

Obviously now you cant fit a sleeve as the wires terminated, many Dno supply cables are not swa or modern swa, so your clamp may be onto something solid anyway. sometimes even lead.

We fit a lot of lampost cut outs, they use a similar principle and use Jubilee clips as pic below
.
Best not to fiddle with it personally, as you say, your earths good.
https://www.google.com/search?q=rol...i57j0i512l4.5679j0j7&sourceid=chrome&ie=UTF-8

Vicario · 2 Dec 2021

Thanks rocky. Here's a photo. I'll leave it until January and then ask the UKPN fuse blokes. I contacted my electrician, who also said not to worry. It is on the lead incomer.

AdrianUK · 2 Dec 2021

Vicario said:
Thanks rocky. Here's a photo. I'll leave it until January and then ask the UKPN fuse blokes. I contacted my electrician, who also said not to worry. It is on the lead incomer.View attachment 252918

So your "Electrician" has fitted a pipe clamp, intended for use on a hard copper water pipe to a soft lead covered PILC cable and hes says no need to worry! Hmmmmm

The problem is two fold:

Lead is very soft and will flow, at room temperature, when a force is applied. This means that it will move under the clamp and the clamp will become less effective over time (hence why the proper clamp uses a constant pressure spring) - the result of this is that the earth loop impedance will rise. This may lead to a poor contact which might heat up in the event of an earth fault.

Secondly its not unknown that squashing the lead sheath under an inappropriate clamp can lead to the underlying paper insulation being compromised and a short circuit occurring inside the cable.

Harry Bloomfield · 2 Dec 2021

AdrianUK said:
Lead is very soft and will flow, at room temperature, when a force is applied. This means that it will move under the clamp and the clamp will become less effective over time (hence why the proper clamp uses a constant pressure spring) - the result of this is that the earth loop impedance will rise. This may lead to a poor contact which might heat up in the event of an earth fault.

I agree and yes I have come across it. You cannot clamp lead, to make a connection, either a tinned copper wire in a terminal, nor using that style of clamp on the lead sheath of a cable - the lead just creeps out of the way.

Vicario · 24 Jan 2022

Just a quick update. UKPN have fitted a new earth clamp, as recommended on this forum. When my electrician took a reading on the original pipe clamp he got 0.23 ohms. Is there any way that I can get a new reading? I'm a total amateur.

EFLImpudence · 24 Jan 2022

Not really.

It is a reading with a special meter(Earth Fault Loop Impedance meter) of the circuit impedance(resistance) from your house to the substation and back which by necessity has to be done on the live circuit with the earth disconnected from the house installation.

Harry Bloomfield · 24 Jan 2022

Vicario said:
Just a quick update. UKPN have fitted a new earth clamp, as recommended on this forum. When my electrician took a reading on the original pipe clamp he got 0.23 ohms. Is there any way that I can get a new reading? I'm a total amateur.

Not without a major amount of spend for one use of the equipment to test it - maybe ask your electrician?

Vicario · 24 Jan 2022

So will this new clamp do any better?

chivers67 · 24 Jan 2022

I doubt the reading will be much different but the new clamp won't damage your incomer.

Vicario · 24 Jan 2022

My electrician will be coming in the spring to fit an EV charger so I'll ask him to do a test. Just thought I'd post to show that the forum's advice is taken seriously by us amateurs!

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Earth clamp on incoming cable

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Harry Bloomfield

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Vicario

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AdrianUK

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Vicario

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EFLImpudence

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