TNCS High ZE at origin

[AdamGiguere]

Hi there

Testing at origin of a domestic property, I have found:

L-N: 0.44 Ohms
L-E: 9.89 Ohms

I had the DNO attend clients address, there response was that it was quite high and confirmed readings of 0.44 for ZE. (Pleasee attached document with their response)

My concern is they don't seem to have checked the reading between L-E......

Anyone know what could be the cause of this? MET connections are tight and in good condition....

Many thanks in advance.

Adam

 

[AdamGiguere]

I cannot see anywhere that it states that the property is currently a PME system. In fact, the OP says “the 25mm earth comes from elsewhere - I'll have to investigate further” so it looks like it is currently a TT or TNS system. The DNO actually seem to be saying they made a decision to provide PME tails for an electrician of choice to connect into the excising setup. I suspect they have not done this yet and will do the actual conversion when an electrician is present.

Are you sure this is not a TT system?

Hi Davisonp

This sounds like a good translation of their wording.

I'm pretty sure it's not a TT system/although could be mistaken.

I did think perhaps maybe a TNS due to the 0.44 on the L-N

But have been advised by a colleague who came to site with me originally that it's a TNCS.

Hopefully they have a log of their visit and can advise what system it definitely is

 

[westward10]

Is there no earthing conductor from the service head.

 

[AdamGiguere]

Is there no earthing conductor from the service head.

No there isn't possibly could be a TNS then...as I do believe it going out of the meter cupboard and into trunking which then goes in to the ceiling of the porch area....

 

[AdamGiguere]

In future I'll always be getting detailed pics I appreciate all your time guys!!!

Great forum!!

 

[Des 56]

I thought it was only myself that was confused so i refrained from posting anything
Having read the later replies it appears to me I am not alone

Op,can you give a definitive description of the head and the supply type
Is there a separate earth conductor entering the property?

Can you confirm or deny a installation earthing conductor connection has been made
to the Pme at the cut out or elsewhere even?

 

[AdamGiguere]

I thought it was only myself that was confused so i refrained from posting anything
Having read the later replies it appears to me I am not alone

Op,can you give a definitive description of the head and the supply type
Is there a separate earth conductor entering the property?

Can you confirm or deny a installation earthing conductor connection has been made
to the Pme at the cut out or elsewhere even?

Will retrieve pics and post ASAP...I've asked the tenant (family friend) to take a pic or two of the meter cupboard

 

[westward10]

They need to go outside and see if a green/yellow wire drops down the wall.

 

[AdamGiguere]

They need to go outside and see if a green/yellow wire drops down the wall.

I'm pretty certain it doesn't...

If it did it would be unnoticeable/covered from sight...

 

[AdamGiguere]

If they are telling you it is PME and you are getting those readings then you have no link between the earthing conductor and supply neutral.

If there was no link - would I be getting a reading similar to 9 ohms?

I'd expect no reading...?

If so and there is no link - where is the 9 ohms coming from?

 

[westward10]

If there was no link - would I be getting a reading similar to 9 ohms?

I'd expect no reading...?

If so and there is no link - where is the 9 ohms coming from?

We need a clearer picture of what is going on because this has become very confused. I think I wrongly assumed the earthing conductor was connected to the head hence my assumption there was no link to this conductor from the supply neutral.

 

[buzzlightyear]

The cut out does not come with the earth brass bar as shown above the 25mm earth comes from elsewhere - I'll have to investigate further.

.
but reading between the lines i think it is TT supply,read post 1 (tested at supply pole)

 

[AdamGiguere]

.
but reading between the lines i think it is TT supply,read post 1 (tested at supply pole)

I did think this when reading it - supply pole would indicate earth rod...

But if this is the case then they have said 0.33 at the supply pole, I shouldn't be getting a reading of over 9 ohms at the MET should I?

 

[soms]

Are you measuring the Ze with all earthing and bonding conductors connected to the MET? This could result in your 9 ohm reading through an earth path formed by some other extraneous-conductive-part(s)?

 

[buzzlightyear]

 

[buzzlightyear]

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