Main earthing conductor

[gazdkw82]

I took a glance at my CU the other day and noticed the main earthing conductor was terminated into a terminal block and then terminated to the supply earth. This seemed odd to me and also it didn't look very good. Why not terminate it straight to the supply earth? Should I contact my supplier?

 

[rustynails]

TN-S earthing from the sheath of the incoming cable looks very short. You shouldn't.... attach a BS951 clamp to the incoming cable as the cable is the property of the distributor. The looks like a 60amp chocolate box. Depending on the fabric of the wall there you could plug and screw an earth block to the wall then connect into that.

 

[Andy78]

Well it's not right clever is it ? a fixed MET would be the usual method of connecting to the earthing conductor. If you are asking if you can fiddle with the sheath clamp and fix directly to that, that would be a no.

 

[gazdkw82]

isn't that an henley block? or was you referring to the plastic terminal block as a choc box?

 

[gazdkw82]

Well it's not right clever is it ? a fixed MET would be the usual method of connecting to the earthing conductor. If you are asking if you can fiddle with the sheath clamp and fix directly to that, that would be a no.

no im not asking If I can fiddle with it. I was pretty sureit is the responsibility of my supplier, I’m asking if it needs reporting atall. I don’t understand why its cut and then connected to a terminal block andthen another suspect looking green cable goes from other end of that terminalblock onto the earth sheathing. Is that common practice? Isn’t it just interruptingwhat could be a continuous connection between MET and supply earth

 

[Octopus]

no im not asking If I can fiddle with it. I was pretty sureit is the responsibility of my supplier, I’m asking if it needs reporting atall. I don’t understand why its cut and then connected to a terminal block andthen another suspect looking green cable goes from other end of that terminalblock onto the earth sheathing. Is that common practice? Isn’t it just interruptingwhat could be a continuous connection between MET and supply earth

What's the Zl and Ze?

You could get your supplier to look but unless the readings are high I doubt they will be interested!

 

[Richard Burns]

I would suggest that someone at some point has looked at the earth cable on the sheath and said, oh that is too small (probably incorrectly) and then cut the cable and added this new larger green and yellow cable.
This will have no effect, since they left the last bit of cable to the sheath, except to make things more complicated at a later date, such as now.
So long as the terminal block connection is sound and, as Murdoch says, your test results are good then this will be OK ish.
Changing the terminal block to an earth block fixed in place would look better.
Effectively the current state is that the suppliers earth is now just the clamp and small section of cable. So the MET should be directly after that.

 

[gazdkw82]

I get my new MFT soon so ill do a ze reading

 

[hightower]

As others have said, stick an earth block in, something like this maybe. https://www.tlc-direct.co.uk/Products/TLEB4.html

It will essentially just be doing the same job as the current choc block, but will look a little better.

 

[gazdkw82]

If I replace that terminal block with a earth terminal,where do I fix the terminal?? Cant leave it hanging, There’s only about 2 “ onthat little green cable

 

[hightower]

If I replace that terminal block with a earth terminal,where do I fix the terminal?? Cant leave it hanging, There’s only about 2 “ onthat little green cable

Well we can only go off the photo you've posted, but to me it looks like there'll be just enough length to fix it to the wall right next to the clamp.

 

[gazdkw82]

I can try

 

[Octopus]

Well we can only go off the photo you've posted, but to me it looks like there'll be just enough length to fix it to the wall right next to the clamp.

Are you sure. The dno cable looks too short to me and hence why I suspect the choc block was used.

A closer up picky would help.

 

[hightower]

Are you sure.

I'm not, hence why I said we can only go off the photo - to me it looks like it should just be long enough, but the only person who can really say is gazdkw82.

 

[gazdkw82]

worst case scenario I can always fix a timber block to the wall next to It which should make it closer

 

[Risteard]

It's standard practice here to use an ISCO for the MET.

 

[gazdkw82]

What's an Isco?

 

[hightower]

What's an Isco?

Google is your friend:

https://www.google.co.uk/search?q=i...xePMAhXsAsAKHcWABbAQ_AUIBygB&biw=1440&bih=775

 

[gazdkw82]

Is this the same thing

5-Way SP 100A Service Connector Block 25mm² | 100A Connector Block | Screwfix.com

 

[Midwest]

To be honest, the whole thing looks a mess. I personally would call the DNO to have a look at their earth & your suppler to have a look at their tails. Then I would ask the property owner (think that's you), what do they want to do with their tails from the meter to the Henley blocks (i.e. get rid of Henley blocks) and how about supporting that white cable properly, or is it redundant? And quite frankly, the cupboard could do with a bit of a hoover.

 

[gazdkw82]

totally agree it needs a good hoover!! ill make sure the better half knows she is really starting to slack! ;-)

I will call the DNO. I want to get it sorted out because it is a mess!

that white cable is from the house alarm so has nothing to do with anything. Id like to get rid of the Henley blocks. I plan to change the CU, sort tails out and sort the whole thing out. However that will have to wait until I have the right knowledge and experience to do such a job

 

[Midwest]

totally agree it needs a good hoover!! ill make sure the better half knows she is really starting to slack! ;-)

I will call the DNO. I want to get it sorted out because it is a mess!

that white cable is from the house alarm so has nothing to do with anything. Id like to get rid of the Henley blocks. I plan to change the CU, sort tails out and sort the whole thing out. However that will have to wait until I have the right knowledge and experience to do such a job

That's told her! Seriously, wouldn't hurt to ask the DNO to have a shufty at their earthing terminal.

 

[gazdkw82]

Called western power. An electrician called and said its not something they deal with because I'm on a TN-S system. If I was on PME then they would come and sort it. They said to call an electrician who can replace the cable. There's enough of the cable to just undo the existing little bit that's connected to the rod and connect the existing cable from the cu board

 

[telectrix]

undo the clamp nut and bolt replace cable in 1 piece to the henly/MET with a lug on the end for the clamp.

 

[DPG]

I'm confused !?! Daz

 

[gazdkw82]

It will do.

6mm² Copper Tube Lug 6mm Stud Hole Pack of 10 | Crimp Terminals | Screwfix.com

that clamp will be ok won't it?

 

[Midwest]

Flipping DNO's. It's their kit, and it looks carp. I suppose the only way you'll convince them is a high Ze reading. Personally wouldn't replace it myself, case it goes bang, when you tighten it too tight! Think you just gotta whinge a bit, if the reading is bad. Common problem it appears, here's one that 'we' prepared earlier: http://www.electriciansforums.co.uk...ctrical-forum/86475-tns-earth-clamp-bust.html. Hepworth clamp, is what you want, I think that's what they're called.

 

[gazdkw82]

How could it go bang?

 

[davesparks]

How could it go bang?

Don't know until it does it!

 

[Richard Burns]

The clamp looks as if the screw for tightening is the same as the screw for retaining the cable in place.
Admittedly the clamp looks very loose and appears to be held off from the cable sheath by something, however if you were to firmly affix a cable lug (the cable in the picture looks to be larger than the 6mm² you are referencing in the link to the lug you gave) to the clamp then the force applied to clamp the lug will also be applied to tightening the clamp, if the clamp can tighten enough to compress the cores and damage them then they could short to the lead sheath or each other.

That said it does not appear from the picture as if that clamp can tighten beyond a certain point which looks as if it would still be a loose fit on the cable sheath.

A hepworth clamp needs a special tool to close it and uses an earth braid for connection so is not ideal in this case, a constant force spring would be OK but they seem to be hard to obtain easily at a reasonable price.

Since you have had verbal authorisation from the DNO to change the cable it would be worth looking at the job in detail to see what it entails and only proceed once you are sure it is safe and your resulting solution will be secure and effective.

 

[Octopus]

I wouldn't do ANYTHING until you have conducted both a Ze and Zl tests.....

 

[sparksburnout]

is it me or is this thread getting a bit silly? What is the Ze? If there are problems then it is down to the DNO to sort you should not be messing about with any clamp on that cable. Have you asked them if they can supply a PME? Would be by far the best solution for the sake of what it costs, although it would help greatly if you SUPPLIED THE Ze!
Sorry I have just noticed you are a trainee, maybe you need to get an experienced spark round?

 

[gazdkw82]

I am a trainee but I'm capable of doing a Ze. I'll do it this week and see what it says.

Tbh if it's an acceptable reading I'll leave it because although it looks simple to get rid of that terminal block and then terminate the existing cable to the existing clamp it's clear it's not that simple with many factors

 

[sparksburnout]

I am a trainee but I'm capable of doing a Ze. I'll do it this week and see what it says.

Tbh if it's an acceptable reading I'll leave it because although it looks simple to get rid of that terminal block and then terminate the existing cable to the existing clamp it's clear it's not that simple with many factors

If I were you I wouldn't go near the clamp, either leave it alone or get the DNO to sort it. WPD are normally very good over this sort of thing I can't understand why you say the were not interested.

 

[sparksburnout]

The clamp looks as if the screw for tightening is the same as the screw for retaining the cable in place.
Admittedly the clamp looks very loose and appears to be held off from the cable sheath by something, however if you were to firmly affix a cable lug (the cable in the picture looks to be larger than the 6mm² you are referencing in the link to the lug you gave) to the clamp then the force applied to clamp the lug will also be applied to tightening the clamp, if the clamp can tighten enough to compress the cores and damage them then they could short to the lead sheath or each other.

That said it does not appear from the picture as if that clamp can tighten beyond a certain point which looks as if it would still be a loose fit on the cable sheath.

A hepworth clamp needs a special tool to close it and uses an earth braid for connection so is not ideal in this case, a constant force spring would be OK but they seem to be hard to obtain easily at a reasonable price.

Since you have had verbal authorisation from the DNO to change the cable it would be worth looking at the job in detail to see what it entails and only proceed once you are sure it is safe and your resulting solution will be secure and effective.

Your winding him up Richard are you not???

 

[Richard Burns]

Your winding him up Richard are you not???

Just pointing out the less likely problems, in practice I would not think all that much, except about altering the DNO's connections.

 

[Midwest]

How could it go bang?

You might find out if you mess around with that cable, that's been sat there since before the War, annoying no one. I expect that's why the DNO electrician said to crack on, save him a new pair of safety glasses. :wings:

 

[gazdkw82]

I don't understand how it could go bang by sorting the cable? keep in mind im a trainee, can you explain more??

do you mean it could go bag if there is a fault current? or do you mean if the clamp touches the wrong part of the rod whilst moving?

 

[hightower]

I think the guys are saying the insulation could have broken down over all the years it's been installed, but because it is unmoved you might not find out whether it has or hasn't until you come to move it.

 

[Midwest]

I don't understand how it could go bang by sorting the cable? keep in mind im a trainee, can you explain more??

do you mean it could go bag if there is a fault current? or do you mean if the clamp touches the wrong part of the rod whilst moving?

Apologies gazdkw82 for my rather jocular reply. Paper insulated lead sheathed cables (I think that is what you have) have been used by utility companies for quite some years, the 1920's and possibly before, for electrical power distribution. There is no way you could tell the installation date of your installation, but it could be as old as your house. Whilst these cables can withstand the passages of time, and allegedly have very good reliability, your cable has not been moved for some time, and a bit like me, has become set in its ways. Therefore there is not certainty of the state of the internal insulation coverings. Hence in short, if your were to attach a clamp, and tighten said clamp too much, it 'could' cause the internal conductors to short. I'm sure you will understand the consequences of that. Therefore IMHO, I would not alter the earthing clamp on the service cable, leave that for your DNO.