Earthing Supply Type help -High Earth Loop Impedance reading

[grhughes74]

Hi - Wondering if someone can help. I have recently had an extension built on my house. When the electrics were tested the power company reported that I have a High Earth Loop Impedance reading.
The Power Company are saying that my building manager needs to get an electrician to install an Earth Rod to resolve this. My building manager is saying that it is the power company's responsibility to fix this.
I have looked at the wiki about earthing types and I think that mine is either a TN-C-S or TN-S but am hoping that someone could confirm that for me.
I have attached a photo below.
Many thanks
G

//media.diynot.com/53000_52473_48121_96644692_thumb.jpg

 

[grhughes74]

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• grhughes74
• 11 Jul 2012
• 1

This should be the correct photo....

G.

 

[ban-all-sheds]

I think that mine is either a TN-C-S

Picture too murky - I can't see anything linking the earth block to the cutout. Is there anything?

Hard to envisage how if you had a TN-C-S supply which was working OK you could also have a high Ze.

or TN-S

Ditto I can't see a connection between the earth block and the cable sheath.

 

[JohnW2]

Hi - Wondering if someone can help. I have recently had an extension built on my house. When the electrics were tested the power company reported that I have a High Earth Loop Impedance reading. The Power Company are saying that my building manager needs to get an electrician to install an Earth Rod to resolve this. My building manager is saying that it is the power company's responsibility to fix this. I have looked at the wiki about earthing types and I think that mine is either a TN-C-S or TN-S but am hoping that someone could confirm that for me.

Assuming that it is a TN- supply (as BAS says, can't really tell from your photo - any chance of getting a better one?), opinions seem to vary (and/or practices/interpretations vary between DNOs in different parts of the country).

There seems to be general agreement that a DNO has no duty to supply an earth in the first place (i.e. when they first provide an electricity supply). However, if they do (i.e. if it is TN-S or TN-C-S) then some people say that they have a duty to 'maintain' it (i.e. rectify the situation if it ceases to be adequate), and in some parts of the country that certainly happens. However, it seems that this is not necessarily true country-wide.

Kind Regards, John.

 

[grhughes74]

Thanks for all the advice - I appreciate it.
I have added some new, clearer photos below.

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• grhughes74
• 11 Jul 2012
• 1

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• grhughes74
• 11 Jul 2012
• 1

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• grhughes74
• 11 Jul 2012
• 1

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• grhughes74
• 11 Jul 2012
• 1

Many thanks
G

 

[ban-all-sheds]

There seems to be general agreement that a DNO has no duty to supply an earth in the first place (i.e. when they first provide an electricity supply).

(4) Unless he can reasonably conclude that it is inappropriate for reasons of safety, a distributor shall, when providing a new connection at low voltage, make available his supply neutral conductor or, if appropriate, the protective conductor of his network for connection to the protective conductor of the consumer’s installation.

 

[ban-all-sheds]

Hard to envisage how if you had a TN-C-S supply which was working OK you could also have a high Ze.

Flaky connection inside the cutout, I guess..

 

[ban-all-sheds]

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• grhughes74
• 11 Jul 2012
• 1

Well you can't open it up to see, but that looks like TN-C-S to me.

 

[JohnW2]

There seems to be general agreement that a DNO has no duty to supply an earth in the first place (i.e. when they first provide an electricity supply).

(4) Unless he can reasonably conclude that it is inappropriate for reasons of safety, a distributor shall, when providing a new connection at low voltage, make available his supply neutral conductor or, if appropriate, the protective conductor of his network for connection to the protective conductor of the consumer’s installation.

Yes, I should have been careful about the tense of what I wrote. You are quoting 2002 legislation. I was think of those millions of 'well-established' supplies (many of which are 60+ years old), dating from a time when I suspect that no legislation such as that applied to 'new installations'. Even though that cutout appears to have been installed in 1994, 'the supply' (I agree probably now TN-C-S) probably dates back decades earlier than that.

In any event, even today, "unless ... inappropriate for reasons of safety" can presumably mean nothing more than that the TN 'earth', if provided' would have too high a Ze - which is a bit of a potential cop out!!

Kind Regards, John.

 

[Spark123]

I'd have gone for TN-S, what is the Ze reading?

 

[JohnD]

looking at this picture

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• grhughes74
• 11 Jul 2012
• 1

it does not look like TNC-S to me, and I see no PME label.

The bright new earth block looks to me as if it has been positioned so that, when the "installed" label was positioned to hide it, it would give the impression of being TNC-S. No doubt this was an innocent act and not intended to mislead.

I would start by asking if the DNO is willing and able to provide an earth, possibly convert to PME, and what, if anything, they would charge. the incoming cable looks relatively modern, and by no means a 60-year old lead and paper one.

p.s.
those tails look rather thin. The sheathing has been cut back a long way too far outside the enclosure.

 

[JohnW2]

I'd have gone for TN-S, what is the Ze reading?

What do you think that incoming cable is, then - SWA? I had guessed that it was proibably straight con, or something like that.

Kind Regards, John.

 

[JohnW2]

those tails look rather thin.

They do - but, there again, the cutout only appears to be rated for a 60A fuse.

Kind Regards, John.

 

[GaryMo]

I'd have gone for TN-S, what is the Ze reading?

What do you think that incoming cable is, then - SWA? I had guessed that it was proibably straight con, or something like that.

Maybe split concentric and a TN-S supply.

 

[JohnW2]

I'd have gone for TN-S, what is the Ze reading?

What do you think that incoming cable is, then - SWA? I had guessed that it was proibably straight con, or something like that.

Maybe split concentric and a TN-S supply.

That's obviously a possibility - but I thought I'd heard that DNOs didn't use split con very much?

Kind Regards, John.