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Topic Title: PILC Earth Clamp
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Created On: 04 December 2013 07:04 PM
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 04 December 2013 07:04 PM
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Avatar for AncientMariner.
AncientMariner

Posts: 513
Joined: 14 December 2004

Often in this forum reference is made to the use of EC15 or EC14 earth clamps onto the lead sheath of PILC.

Our current house with a TN-S supply, prior to 2002 had a supply via underground PILC into the original cutout as fitted by MANWEB in the late 1950's. Prior to 2002 all electrical works had been carried out by MANWEB's staff/contractors, so could be assumed to comply with both IEE and DNO regs.

The earth connection to the lead sheath was by the use of a clip like this:-

https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcS3rAcvLZCnTkp8CltR7DLgHiCDgHPwYdXnAxqii3vPN8IxemFiwA

Sorry for long link.

Whilst I can understand how an EC14 or EC15 clamp can cause damage, I cannot see how the clamp that we had could be expected to provide a low resistance connection long term. A sweated connection would have been better,

But the question is, why was it in the 1950's/60's where PILC was the norm for underground use that there was no internal provision for an earth connection to the lead sheath? There were then plenty of skilled PILC jointers.

In 1973 our newbuilt house, again TN-S, was supplied with split concentric cable (looped from next door who were supplied via PILC) Our cut out terminated all three connections, Live, Neutral and Earth. Yet back to our current house, in 2002 we had the cutout/meter moved and split concentric was jointed underground to the PILC and the PILC brought into a built in meter box (previously the cutout and meter were under the stairs). The new cutout had no provision for the earth conductors so these strands were left long and after taping with gn/yl tape were connected into a SP PowerSystems earth terminal screwed to the meter board.

Progress?

(I have posted before that when the cut out was moved in 2002, the jointer asked whether I - as a mere householder - wanted PME. I declined.)

Cheers!

Clive

-------------------------
Clive S Carver GCGI IEng MIET
 04 December 2013 08:47 PM
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Avatar for UKPN.
UKPN

Posts: 501
Joined: 17 January 2012

If your query is why was the sheath of the lead cable not plumbed, the answer is, it was, in many, many cases. but It was time consuming, cost, and the loop was not a great impedance. Furthermore, the facility was not always used, the water main was invariably better!
As regards splits,SWAs, CNEs-thats another story. Hope this helps!

Regards.
 04 December 2013 08:56 PM
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Avatar for OMS.
OMS

Posts: 19602
Joined: 23 March 2004

but It was time consuming, cost, and the loop was not a great impedance


Really ? - I've wiped a few in my time and the impact on loop impedance is almost imperceptible if done properly. I fyou know what you are doing then they are not a long job, and cost is minimal.

Difficult to imagine a water main being a better R2 than the cable lead sheath itself as there will be a big chunk of mud between it and the source electrode

Regards

OMS

-------------------------
Failure is always an option
 04 December 2013 09:09 PM
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Avatar for UKPN.
UKPN

Posts: 501
Joined: 17 January 2012

In this case, you are ahead of me with experience, but in the London/Essex area the sheaths are returning .7s and above on a regular basis and I see many plumbed 7.029s just wound up behind the meter
board. With bonds just on the water you can get .5 and lower. Add gas and even lower.
 04 December 2013 09:59 PM
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daveparry1

Posts: 6163
Joined: 04 July 2007

That 0.5 ohms on the water is due to a neighbouring property being tncs though isn't it UKPN? I see that quite often in my area where there's a lot of overhead supply, (lots of 1960's properties) quite often the only earth is to the water main in which case when I do a c/unit change I put a rod in and get say 60-80 ohms on the rod but when the bonding is back on I often get a Zs of 0.5 ohms!

Dave.
 04 December 2013 10:20 PM
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alancapon

Posts: 5760
Joined: 27 December 2005

We are still replacing these clips with sweated connections. We were the last DNO in the British Isles to be installing PILC, and I suspect we are the last to carry out hot works on lead.

Regards,

Alan.
 05 December 2013 08:25 AM
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John Peckham

Posts: 7408
Joined: 23 April 2005

I understand that in the old LEB/EDF/UKPN area the practice of sweating earthing conductors was stopped as it involved hot works inside the consumers premises and the attendant risks with a few incidents thrown in. They now use constant pressure springs and a braided earth connected to an MET. They were using BS951 clamps up until 2005 to my certain knowledge.

-------------------------
John Peckham

http://www.astutetechnicalservices.co.uk/
 09 April 2014 08:12 AM
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kmu47

Posts: 1
Joined: 08 April 2014

Hello John, isee this is an old forum discussion, but i have used these clamp meters a while now and i am very thrilled about them, they have been a great help for me at home and at work, i canĀ“t really describe here how they work, it would be too long i reckon for this forum but i know where you can get more info and products, Clamp Meters are very handy tools to establish currents indirectly and easy to use. You do not have to interrupt the circuit to make a measurement with your clamp meter, because clamp meters measure the magnetic effect of the electricity field around the wire or conductor.
I will keep a look here if any reply comes, and hope I can help along the line ok.
best regards
kmu
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