Which earthing system is this?

[hillbillie]

I recently passed my part P but don't have much experience. I'm rewiring my flat and am conused/perturbed about much of what I see.

The kitchen fitters called my earthing arrangements TN-S when they did the kitchen in 2008, presumably because they saw a bit of twisted unsheathed wire connected to a screw above the neutral bar. I took their word for it. However, yesterday EDF's subcontractors came to fit a cut out for me and opened the service head. They walked out refusing to touch it as it was VIR and they were worried it would break.

Anyway, they left the service head open and I have a set of tails I can use to replace the old ones (though the supply cables coming in seems also to be VIR).

My problem is that I can see no earth. The bit of wire above the neutral bar in the C/U disappears behind the fuses but does not come from the sevice head and I can see no clamp etc as the incoming cable is in a metal conduit right up to the service head. I don't want to remove the fuse bar in case the old VIR tails snap (I'd rather not replace them until I have my new C/U in place and wired up)

Can anyone help please? Am I missing something obvious or should I either contact the DNO or go and buy a spike and create a TT system?

Please have a look at the photos:

 

[jpmiff]

have you checked the Ze with a meter, this will confirm if you have an earth or not

 

[Spudnik]

Not 100% sure, but most flat installations of this age are TNS, as the earth is supplied via the conduit or trunking system throughout the building.

Yours is connected to the service head via conduit.

Put your meter on there and see what Ze reading you get.

 

[dsb electrical]

make sure to remove external earthing paths to make sure you have a main incoming earth and not relying on the water or gas pipe work for a main earth

 

[DurhamSparky]

looks like TN S as already stipulated...

 

[Jon Bridges]

So if this is TNS does that mean the MET is the 100% green cable which is screwed to the really old style CCU. What BS no is this type?

 

[Spudnik]

Yes it is, and just below it, you can see the cpc's twisted together and screwed to the enclosure also.

 

[hillbillie]

Many thanks for all the replies. Another flat in my block has an obvious earth coming from the sheath of the incoming cable. I see none and assumed the main earth must be the twisted bare wire connected to the CU case. I now realise this twisted wire is actually 2 CPCs. I have a small block above the CU, connected to which is the bonding from the water pipe the earth from my second (economy 7 storage heater) CU and the 100% green earth visible in the jpegs connected to the casing of the CU.

Wifey is watching strictly come dancing, I'll ask her permission after it is over to switch off and check the Ze. I presume I'll have to just remove the 100% green earth connecting the CU to the block, at the block and put my earth lead on this

 

[nickblake]

As they guys have said looks like a TNS what i would do is to Call the DNO and say your supply cable is in poor condition they should come and replace it , it does need replacing urgently especially as you have said you are starting to rewire ,

 

[hillbillie]

As they guys have said looks like a TNS what i would do is to Call the DNO and say your supply cable is in poor condition they should come and replace it , it does need replacing urgently especially as you have said you are starting to rewire ,

I will call them tomorrow and no doubt I'll have to persist when the DNO try to pass the buck to someone else.

And I did get a Ze...0.23 ohms. I removed the green earth wire from the block and also disconnected the cpcs from the enclosure too.

I had a look at my (fellow ground floor) neighbours system and they also have no obvious earth from a cable sheath but the have cpcs connected to the metal enclosure, so I'm guessing you were all right and the earthing is through the metal conduit.

Many thanks again for all your replies.

 

[hillbillie]

The DNO are sending someone within the next 24 hrs!

And a bloke from Napit suggested I set up a TT system if the DNO won't change anything.