Supply Earth connection

[Richard]

Hi illuminati,

First post so be gentle.

Just doing a re-wire on an extension.

Customer had a new DB fitted 12 months ago but has no certificates.

1st thing I checked was supply and type of earthing.

TNS though found that the head earth is connected to lead sheath of supply cable, connected with a standard bonding clamp which was loose.

I obviously re-tightened it, though with this being a compression connection on lead will work loose again over time.

I contacted United Utilities to come and check this out. Over the phone they explained that they use a sprung connection now, and would check it out.

They came in my absence and tested the connection and told the owner it was within limits, which it would now after I re-tightened it.

Has anyone else seen this type of supply earth connection and should I leave it that way?

Thanks

 

[Andy™]

951 clamps should not be used on lead, but they often are. they can compress the lead, and too much compression = big bang.

if you hadnt of tampered with it, then they may well have replaced it.

newer method is a constant force spring (used for earth connection in resin joints etc)

 

[Richard]

I could hardly leave then with a loose connection could I.

Should I persist and get them back?

 

[sparkytim]

Millions of them around just like it, if your Ze is now ok then its not your problem, it belongs to the DNO and if they are happy with it then leave well alone.

 

[Andy™]

I could hardly leave then with a loose connection could I.

you could have left it in the time it takes DNO to arrive...

 

[mole2006]

Just think you could have left it and if something had happened before the DNO arrive, it would be on your conscience. Think you did the right thing.

 

[Evans Electric]

That was a typical DNO response in my opinion , they say the standard earth clamp should not be used , turn up on site, presumably do a Ze and declare it safe . Why not fit a constant pressure clip or sweat it on ?? No leave it and lets get down the caff!!!

 

[NozSpark]

IMHO you should have just called the supplier stating that your customer has a loose earth clamp an that their Ze is out of limits. They will then arrange for someone to come out and have a look. They will also tell you to isolate the electrical installation.

Tightening a BS951 clamp on a lead sheathed incommer is not something id do... too risky!!!

 

[Apache]

Give it a week, loosen the clamp and ring them back!

 

[Tooold]

Whatever you do dont forget to note it on your cert if it stays with a clamp. Not sure you could do owt else so as long as customer knows and its documented you aint happy. As said a lot are used and DNO reluctant to change them.

 

[Lurch]

I could hardly leave then with a loose connection could I.

While your intentions were good your actions were incompetent lunacy. I would not tighten a 951 clamp, or any other type of clamp, on a live lead sheathed cable. Would the customer be any happier once you'd blown the front of the house off? There's things we do that aren't quite to guidelines that are accepted practice, but this is not one of them.

 

[Doc Hudson]

Hi illuminati,First post so be gentle.

Just doing a re-wire on an extension.

Customer had a new DB fitted 12 months ago but has no certificates.....

Thanks

Welcome to the forum Richard. Why didn't you pursue the original electrician who replaced the CU for the EIC and the Part-P compliance certificate? Surely if some of his work was non compliant as you suggest, the original electrician should come back and rectify free of charge. Or go through his scheme provider complaint procedure to get someone to do it. Rather than the customer paying for extras that they shouldn't have to pay for. Isn't this what the warranty bit was meant to cover on the Part P scheme?

Doc H.

 

[Doc Hudson]

While your intentions were good your actions were incompetent lunacy. I would not tighten a 951 clamp, or any other type of clamp, on a live lead sheathed cable. Would the customer be any happier once you'd blown the front of the house off? There's things we do that aren't quite to guidelines that are accepted practice, but this is not one of them.

As far as I understand things Lurch has just sligthly paraphrased the NICEIC guidance on this topic. Which is basically you don't mess around with any clamps onto any distributors incoming cable. Its in one of their books somewhere?

Doc H.

 

[a1spark]

Just a thought here !

Now I am well aware of the fact that BS 951 does not allow for the connection of this type of clamp to sheaths of Lead cables or soft metal pipes { Gas, water etc}

How many BS 951 clamps have we seen installed on Lead Sheathed cables....Personally I of course have not counted ,But the vast majority of that type of supply cable I have come across in all my years of Sparking have them fitted, many by the DNO in fact.

Conversely',how many instances of Shorting out of the internal conductors have you come across....personally I have never heard of one instance.

Interesting points dont youi think ?

a1spark.

 

[ianmacd]

A clamp to BS 951 should state in its instructions (if you ever see them) that its not suitable for connecting to a cable but only to a pipe (of sufficiently hard metal).

 

[kme]

I could hardly leave then with a loose connection could I.Should I persist and get them back?

While your intentions were good your actions were incompetent lunacy. I would not tighten a 951 clamp, or any other type of clamp, on a live lead sheathed cable. Would the customer be any happier once you'd blown the front of the house off? There's things we do that aren't quite to guidelines that are accepted practice, but this is not one of them.

I must agree with Lurch here - that particular item, does NOT form part of the customer`s installation; it is owned and maintained by the DNO.

If your live tail fell out of the cutout because vibration had loosened the screws, would you open the cutout to replace it? I hope not.

get an old piece of lead water pipe; and tighten a BS951 clamp onto it; whilst looking down the inside of the pipe. You may then understand what could have happened!

How many BS 951 clamps have we seen installed on Lead Sheathed cables....Personally I of course have not counted ,But the vast majority of that type of supply cable I have come across in all my years of Sparking have them fitted, many by the DNO in fact.

Conversely',how many instances of Shorting out of the internal conductors have you come across....personally I have never heard of one instance.

Interesting points dont youi think ?

Not really, mate. How many house fires have you, personally, heard of which were attributed to a 1.5mm T+E cable on a 20A radial circuit, etc?

I`ve never heard of any, yet have seen this done a number of times. That doesn`t make it safe!!!!!

KME

 

[Andy™]

Conversely',how many instances of Shorting out of the internal conductors have you come across....personally I have never heard of one instance.

ive seen a service head on the wall, with a molten lump of cable/lead on the floor. i dont think it was caused by a 951 clamp being too tight, but if it was, the end result would be almost identical

 

[Richard]

Thanks for the comments, seems I have started some debate.

The original sparky who installed the Dist did a runner, not contactable apparently.

Customer just wants it sorted.

I would have called the DNO as soon as I identified the problem but the customer didn't know who they were. Me not being from that area had to research it later on line.

Is there a standard help line to find this out?

Even then their own technical help line on their website wasn't recognised. Had to ring head office before being put through to right department.

If the risk of shorting the supply cable is so great, shouldn't the DNO have a duty to reduce that risk?

I did consider the possibility of shorting the supply and that the DNO had fitted the 951 clamp or was it the previous sparky, that was why I asked the DNO to check it out as soon as I found out who it was. Sadly I couldn't be there when they called.

Is there some one on this forum who works/worked for a DNO who could comment?

May be I should complain to the DNO.

If I do mark on cert that I ain't happy and some thing happens later who do they persue, me or the DNO?

 

[kme]

You can mark it on the cert (omitting that you tightened it up!), and it doesn`t come back on you.

SparkSS is a DNO jointer- haven`t seen him in a while, though........

KME

 

[Andy™]

If the risk of shorting the supply cable is so great, shouldn't the DNO have a duty to reduce that risk?

why should DNO be expected to make every cable crush resistant so it doesnt get damaged by those who stick a 951 clamp on it.

maybe all T&E should be made with fixing holes, so it doesnt get damaged when i put a nail through to hold into wall, because i dont want to use the correct clips.