A cople of earthing questions

[Lectrician]

Here is my current service head and meter.

I only moved in at the end of November - believe me, a new CU is on the cards - Plenty of other things to be done first

You can clearly see this is a TN-S system, but looks very much like a TN-C-S with the covers on. A trained eye can distinguish bewteen a 16mm split concentric and a 16mm straight concentric, but a 25mm straight concentric looks very very similar to a 16mm split concentric.

 

[bernardgreen]

To me it look like half the outer strands are into the neutral block and the other half of the same layer are into the earth block.

If that is the case then it is the same as having the N E link fitted.

 

[Lectrician]

To me it look like half the outer strands are into the neutral block and the other half of the same layer are into the earth block.

If that is the case then it is the same as having the N E link fitted.

You clearly have no idea what a SPLIT CONCENTRIC cable looks like then

This is why I posted this, as FAR TOO MANY PEOPLE assume a single cable to a head is PME - In atleast 50% of the cases in my area they ARE TN-S!!!

Notice that the N to E link IS NOT INSTALLED.

Take a look into split concentric in other posts, look for my pics of it being stripped back, my link below:

CLICKY

 

[Paper Spark]

Pre Harmonised Split Concentric

RF Lighting wrote:

Who else can get away with cables in a cavity?

It seems the old NORWEB could as well

 

[securespark]

RF Lighting wrote:

Who else can get away with cables in a cavity?

It seems the old NORWEB could as well

In my experience, all the DNO's did WTF they liked, reg or not.

Same with BT.

Especially with regard to cable routes.

UU (ex-Norweb) came to fix some cable damage in the road outside my driveway.

The cable joint ended up 2" below the concrete slabs laid next to the kerb.....

BTW, I agree with you Lec, I see many completion certs filled in with TN-C-S as the supply type, but often they are TN-S. It is sometimes very difficult to tell, as the cut-out is sealed up, but in my experience, the pvc cable used for TN-S supplies is fatter than that for PME.

Lads see the earth leaving the cut-out & think "PME", but it is often TN-S.

 

[bernardgreen]

You clearly have no idea what a SPLIT CONCENTRIC cable looks like then

This is why I posted this, as FAR TOO MANY PEOPLE assume a single cable to a head is PME - In at least 50% of the cases in my area they ARE TN-S!!!

OK I admit to being ignorant. But based on what I have seen on at least one occasion where there was NO separation between the strands of the outers.

Regards

 

[RF Lighting]

You clearly have no idea what a SPLIT CONCENTRIC cable looks like then

This is why I posted this, as FAR TOO MANY PEOPLE assume a single cable to a head is PME - In at least 50% of the cases in my area they ARE TN-S!!!

OK I admit to being ignorant. But based on what I have seen on at least one occasion where there was NO separation between the strands of the outers.

Regards

There are two types.

Tho one you describe is a straight concentric cable it has a live surrounded by just the combined uninsulated earth/neutral strands

The type in the photos above is a split concentric cable. It has a live surrounded by insulated neutral conductors, and uninsulated earth conductors.

This is straight con cable

 

[kai]

That was naughty, dismantling a live service fuse unit, didn't the bitumen compound normally found in these units, fall out of the bottom of the unit when you opened it?

 

[securespark]

The modern-cabled cut-outs are not filled.

 

[Lectrician]

Old lead cutouts are filled, and I would never go near one of those

Naughty, yes - But informative

My link above has good piccies

 

[securespark]

It's not naughty. Lec found them like that, and did a service to the customer by pointing out the dangers and getting the DNO in to rectify.

Didn't you, Lec??

 

[DJM]

Thanks for the PEM information.

Sorry if I am being slow, but anybody wnat to expand on my second question

How bad is unsheathed twisted (steel?) earth running around the house

DESL replied

older systems (60's) had twin VIR with seperate multi core steel wire as cpc. Also main earthing conductor of steel wire was used normally connected to outer sheath of incomer via a clamp or sometimes sweated on.

but nobody expanded, or I missed the sublties of the reply.