Type of earthing system?

timhoward

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• Aug 6, 2021

• #2

This one causes confusion
SNE = separate neutral and earth
The sticker looks fairly recent and I’d put a fiver on TNS
Last time I had this I measured pscc and pefc and found them sufficiently different to conclude it was certainly TNS.

 

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newfutile

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• Aug 6, 2021

• #3

The ZE is 0.1 ohms and similar line to neutral , do they use different size cable for the earth and neutral ?

 

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westward10

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• Aug 6, 2021

• #4

Unlike the old TN-S supply cables we expect to see modern SNE supplies will use split concentric cables.

 

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timhoward

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• Aug 6, 2021

• #5

I was about to say splitcon? In which case you may not detect difference.
I guess next thing is to look at reasons it might mattter since you are below tncs threshold anyway.
Is main earth/bond at least 10mm?
Any relevant special locations or car charger about to be installed?
I see no reason not to believe the sign anyway!

 

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Resu

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• Aug 6, 2021

• #6

newfutile said:

The ZE is 0.1 ohms and similar line to neutral , do they use different size cable for the earth and neutral ?

Click to expand...

See this link.

 

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UNG

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• Aug 6, 2021

• #7

newfutile said:

What type of earthing system is this?

Click to expand...

Is this in a flat as the red fuse holder would suggest it's a solid link and it's fed from a Ryefield or similar distribution set up

 

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pc1966

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• Aug 6, 2021

• #8

UNG said:

Is this in a flat as the red fuse holder would suggest it's a solid link and it's fed from a Ryefield or similar distribution set up

Click to expand...

Could be like my flat: TN-S at the head (red link) but seems to be TN-C-S at the Ryefield (actually Lucy) board down in the hallway.

Determining TN-S or TN-C-S by measurement is hard to do. If the PEFC is much lower than the PSCC then it is clear, but on split con cable back to some linked point both N & E are often identical conductors so your measurements will be very similar.

If you have a low-ish PFC, so Ze in the 0.3 ohm or more region, then you have a sporting chance of measuring N-E resistance (with care, power off but at input of isolator, MET not bonded to avoid links via service pipes, etc) to see if it is comparable to Ze (so a long length of N linked to E way back and similar to the estimated L distance/impedance). If you get near-zero then it is clearly linked at the cut-out! Here having Ze near 0.1 is surprisingly low hence my original though about where the N-E link really is (as it is always linked somewhere/somehow).

But as I found in my flat being TN-S at the cut-out is no guarantee that are not really on a PME supply. However, they say SNE so TN-S and unless it is ground floor for EV charger, etc, it is simpler just to go with that!

 

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newfutile

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• Aug 9, 2021

• #9

They are flats fed from a Lucy board i am conducting an EICR for the communal areas , just wondered what box to tick ? Although i have been told almost everything is PME at some point these days.

 

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MJPD29

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• Aug 10, 2021

• #10

newfutile said:

They are flats fed from a Lucy board i am conducting an EICR for the communal areas , just wondered what box to tick ? Although i have been told almost everything is PME at some point these days.

Click to expand...

You can only tick the box for what you have in front of you

 

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• Sep 7, 2021

• #11

If you remove the black X shaped bung you should be able to see if the block is one piece between neutral and earth, if it is you have PME.

 

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James

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• Sep 8, 2021

• #12

The notice label to the right of the cut out says PME

 

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telectrix

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• Sep 8, 2021

• #13

James said:

The notice label to the right of the cut out says PME

Click to expand...

maybe they don't have labels printed with SNE?

 

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