Cofused earthing arangement

[ajelec10]

Has any body come across an eathing arrangement like this it just cant make its mind up TN-S or TN-C-S
lol.
AJ

 

[Spudnik]

ummmmm why have you taken the whole cutout apart????

Anyways, is the neutral incoming connection point linked to the earth block?

If not then its tns.

A quick Ze would tell you.

 

[Mark.W]

Looks like a TN-S to me, is that a clamp on the sheath in pic1?

 

[mechelec]

It is TNCS supply I think. If you look closely it looks like there is a link between the neutral and earth blocks. there is also what looks like a hepbond from the cable sheath to the neutral block. Agree with Jason why have you stripped the DNOs cutout. try to remember that the cutout you are messing with could be protected by up to 630A fuses at the sub!!!! they rely on service cables burning themselves back to clear faults so my advice is dont play

 

[baldsparkies]

Check for continuity between the earth block and neutral (I don't think its linked looking at the picture)
My own opinion it's TN-S. What Ze are you getting ? thats the clue. if its above 0.35 TN-S is the safer option. Talking of safe,

Pleeeeese be careful you are in harms way with the cut out exposed like that. PFC under short is going to be a whopper

 

[ajelec10]

There was a clamp on the sheath and there is a link between n-e, can't rememver the ZE off the top of me head, and the reason i took the cut out appart is to investigate the type of earthing arangement as it was not clear, you are allowed to remove the suppliers cut out to replace the meter tails if there is not an isolation switch provided. if the cut out is the only point of isolation then you can remove it don't do it under load though.

 

[Gravid]

I'd go for TNS as well, because of the clamp.

 

[Mac]

Definitely TNS.Clamp on the incomer.

 

[ajelec10]

But can you just asume that with out taking it apart and taking more readings which as aleady said you shouldn't be messing around with it, it could of been a TN-S eathing arangement and for some reason the connection became unstable in the road so instead of repairing it they coverted it to TN-C-S eatrhing the sheath from the nutural block as there is certinly a link between N-E,

 

[Mac]

But can you just asume that with out taking it apart and taking more readings which as aleady said you shouldn't be messing around with it, it could of been a TN-S eathing arangement and for some reason the connection became unstable in the road so instead of repairing it they coverted it to TN-C-S eatrhing the sheath from the nutural block as there is certinly a link between N-E,

If it was converted,why is the 16mm still coming from the earth clamp on the incomer.What are your ZE readings mate.Where do the 3 10mm earth cables go

 

[not clever]

TNC-s because the link is in place between the neutral terminal & MET.

Probably a converted TNS, my money would be on a high Ze as TNS so dno converted to TNC-S.

What Ze reading are you getting when doing PSCC & PFC?

 

[baldsparkies]

If the Ze with all bonding disconnected is higher than 0.35 I would go for tn-s maximum there is 0.8. My only reservation on this is it doesn't look like a Supply PME system from the photo's. The danger is that someone other than the supply authorities have put the link in, and that doesn't make it a true pme system. The substation type and proximity to your cut out are all important factors, You really need to verify your Ze as a starting point to verify the earthing type.

 

[Mac]

Sorry mate,looked at the picture again.Looks like it may have been connected up wrong.16mm from incomer should go to the board,and then your 10mm to the gas and water supplies.IMO that's what it look's like.Definitely TNS

 

[baldsparkies]

Sorry mate,looked at the picture again.Looks like it may have been connected up wrong.16mm from incomer should go to the board,and then your 10mm to the gas and water supplies.IMO that's what it look's like.Definitely TNS

I agree with Mac TN-S would not be happy calling what we see PME TNC-S.

 

[ezzzekiel]

the only way to really tell is by looking for the link between neut/earth behind the neut terminal cover, which of course is not allowed as you dont have a pto to open the cutout, so taking a reading and comparing it with your visual is the only way to get an idea of the system type or ring the dno for confirmation.