Difficult Service head

[Lorzor]

Hello all,

I've recently put a new circuit in a house and when filling out my EIC, I needed to access the service head (attached).

I'm relatively new to this and I'm struggling here.

In order to access ANY part of this, you have to pull the main fuse and I had to cut a few metal tallys off. As you can see on the left is where the main fuse sits, to the right there is a cover for the MET and underneath is a cover for the incoming cables. The black box between the meter and thefuse housing is not removable - I can't see where the main earth is. The earth cable you can see is bonding from the gas pipe.

Also, immediately I thought it was a TNS system but it gets quite strange. The what looks like SWA is not SWA, it looks and feels like copper!! IT DEFINITELY isn't steel. Additionally, I can't find a neutral anywhere, I can't see if it is in with the red incoming wire but I'd be pretty surprised if it was.

Could the copper SWA (I know) actually be the PME neutral and we are actually looking at a TNCS system here?

Either way, I have never seen anything like this cable before.

Thanks in advance, I genuinely don't know if I'm just being stupid or inexperienced here but I'm kinda stuck with a way ahead.

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[sparksburnout]

Well, I'm sure the guy from WPD will be very impressed with those qualifications when he comes to put his service head back together. Let us know what he says?

 

[DPG]

I understand that I may have been hasty to take apart the service head but I have a job to do and I don't want to be wasting time. I'm not going to lose any sleep about cutting some tallies off. I'll phone up the suppliers, If they're going to get upset about it then I'll take it up with them.

Now to sound like a complete -------: while I'm new to the domestic game (and service heads!), I am an electrical engineer trained to degree level through an apprenticeship with 15 years experience in industrial electrics.

Back to the original problem: I've finally found the water bond behind a kitchen panel underneath the sink. I have absolutely no idea where it goes. Every single cable that exits the consumer unit goes up some trunking straight in to the ceiling void. There is no TT spike or cabling anywhere to be found.

What continuity reading do you get between the water bond cable in the kitchen and the consumer unit earth bar?
Daz

 

[Lorzor]

Well, I'm sure the guy from WPD will be very impressed with those qualifications when he comes to put his service head back together. Let us know what he says?

It is back together. It is just missing 2 metal tallies.

If someone is going to call me poorly trained then I think I have a right to reply to that.

 

[SparkyChick]

Back to the original problem: I've finally found the water bond behind a kitchen panel underneath the sink. I have absolutely no idea where it goes. Every single cable that exits the consumer unit goes up some trunking straight in to the ceiling void. There is no TT spike or cabling anywhere to be found.

My advice is Isolate the property, disconnect the bonding conductors from the CU earth bar and use a wander lead to continuity check each conductor in turn to try and identify where they go from the CU. This verification is part of the EIC anyhow so you're not going to lose anything by doing this.

 

[Taylortwocities]

There is no TT spike or cabling anywhere to be found.

That may be because somebody decided to turn the TT into a DIY TNCS.

But as above. It doesn't matter if you have a job to do. Unless you really know what you are doing, (and with respect, you have demonstrated that you don't) what you have done is dangerous. There's nothing between the base of that old, shaky looking service head and the substation, maybe a 600A fuse there. Instant meltdown and ambulance if you get it wrong.

 

[Lorzor]

That may be because somebody decided to turn the TT into a DIY TNCS.

But as above. It doesn't matter if you have a job to do. Unless you really know what you are doing, (and with respect, you have demonstrated that you don't) what you have done is dangerous. There's nothing between the base of that old, shaky looking service head and the substation, maybe a 600A fuse there. Instant meltdown and ambulance if you get it wrong.

I understand that I would be shaking hands with the grid should I come in contact with that. I have industrial matting and gloves for just such an occasion.

I know this looks like I've just started willy nilly taking stuff apart and yes my inexperience shows but I can assure you that it was at least conducted safely.

Thank you to everyone who has pointed that out - I won't do it again

 

[DPG]

And faceshield hopefully.

 

[hightower]

What have your Ze tests shown (with any bonding removed)?

 

[Lorzor]

What continuity reading do you get between the water bond cable in the kitchen and the consumer unit earth bar?
Daz

I've just got out the wandering lead and it's 0.02 ohms, so I'm pretty sure it's connected directly to the consumer unit earth bar.

I'm still no closer to finding how this place is earthed. I give up. I'm going to phone someone.

 

[SparkyChick]

How many earthing conductors do you have in the CU (obviously excluding the CPCs for the various circuits)?

 

[Lorzor]

What have your Ze tests shown (with any bonding removed)?

This is the whole problem.

IF the supply is TNCS then technically I can't do the test without taking the service head apart and people get really shitty about that, apparently.

Because you shouldn't have to take the head apart - it may suggest that this is a TT system so I'm going to conduct the test from the consumer unit - in hindsight, is something I should have done right at the start. If it's a nice high reading then I would have known this was a TT system from the start.

 

[PEG]

Hi dude,the world won't end,and we have all done madder things...just don't talk about it,and provide pictures.
The original information you seek,may have been found with a phone call.

What type of property is it?

Do some deleting,have a think,and come back to us.

 

[Des 56]

That 10mm or 16mm green /yellow is probably your earthing conductor from the cut out to your consumer unit
You can verify with a continuity test
At the consumer unit you may then find some bonding cables for services

At the consumer unit disconnect the earthing conductor and measure Ze,if the reading is within the 0.35 it may likely be Tnc-s,however,only the supplier can verify that it is indeed Tnc-s and we have to rely on a Pme sticker telling us or to ask them
They have an obligation to inform you of the type of earthing that they may or may not provide

 

[Midwest]

To add my measly morsel, that service head would 'appear' to bear the resemblance of a PME supply, with a very poorly terminated neutral, normally covered in a nice black plastic boot not a black plastic box?

I also see the main fuse, and the detachable cover to the service head neutral. Worryingly, there doesn't seem to be an earthing conductor connected into the service head neutral (OP suggests the one in the picture is connected to gas service pipe?), which suggest it's missing or it's not a PME supply. Phone to the DNO in that case, to clarify (unless you find an earth rod somewhere!), and perhaps they might have a view on their service cable termination?

As an aside, removal of DNO seals (please no Pinnipeds jokes ), varies by different DNO. Mine SSEN, allow electricians in government approved schemes, to remove seals where necessary, remove main fuse, to carry out work on customers tails. Replace main fuse, put on SSEN temporary seal and ring them with details. Check with your DNO to find their policy on seal removal.

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[hightower]

This is the whole problem.

IF the supply is TNCS then technically I can't do the test without taking the service head apart and people get really shitty about that, apparently.

No mate, you disconnect at the MET (within the Consumer Unit) if that's all you can do (I say that as some modern heads have holes in the head for test probes).

If it's a high reading it'll probably be TT. If it's a low Ze reading, it could be TNCS - one way to affirm more (apart from phoning DNO) is to then carry out a Zl. If Zl is the same reading as Ze, then there's a good chance it's TNCS.