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Topic Title: Where is the earth?
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Created On: 13 August 2014 06:45 PM
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 13 August 2014 06:45 PM
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alanblaby

Posts: 389
Joined: 09 March 2012

I did an EICR today on a flat.
Typical late 1940's/50's install, everything original, apart from the meter.

My first look was at earthing and bonding.
No (visible) earth conductor, and no bonding to gas or water.
OK, so I do a R1+R2 for a socket outlet, IR, then a Zs.

Amazingly, the Zs was 0.55 Ohms.

So clearly there was an earth coming from somewhere, I looked again at the really old metal clad fusebox, but nothing evident there, though not all cables could be identified.
The fusebox was mounted on a wooden board, with no conduit feeding it.
OK, one of the cables in the earth bar could be an earth, possibly a TT install with a buried rod and plastered over cable.

Any other ideas where it could have got the earth from?

And, overall, the install was truly dreadful, but no C1's, but 30+ C2's.
Thanks
Alan.
 13 August 2014 06:54 PM
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John Peckham

Posts: 7509
Joined: 23 April 2005

CPC to boiler, immersion or gas cooker. Or perhaps neutral earth fault which is very common as it passes the 240V bang test.

-------------------------
John Peckham

http://www.astutetechnicalservices.co.uk/
 13 August 2014 07:08 PM
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daveparry1

Posts: 6239
Joined: 04 July 2007

Quite possibly there's a bonding conductor buried in the wall and going to the lead water main, now if next door is on the same water pipe
and happens to be tncs you will get a very good Zs/Ze!
 13 August 2014 07:24 PM
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Gutterball

Posts: 15
Joined: 28 June 2011

the water pipe used to be used for an earth.
 13 August 2014 07:31 PM
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daveparry1

Posts: 6239
Joined: 04 July 2007

Yes it did up until around the mid sixties.
 13 August 2014 07:50 PM
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alanblaby

Posts: 389
Joined: 09 March 2012

Yes, thanks, it could well be a buried pipe - I havent seen such an original condition place before, it has had new kitchen units - all 2 of them, in around the lates 1970's I'd guess, and 2 socket outlets have new faces, but otherwise it looks totally original.
Not in a nice way, it is mouldy everywhere.

I didnt want to disturb any wires as they were flaking away, so I'll just be giving it aload of C2's and it can be sorted then.
Thanks
Alan.
 13 August 2014 09:09 PM
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Jaymack

Posts: 4668
Joined: 07 April 2004

Originally posted by: alanblaby
I did an EICR today on a flat.
No (visible) earth conductor, and no bonding to gas or water.
So clearly there was an earth coming from somewhere, I looked again at the really old metal clad fusebox, but nothing evident there, though not all cables could be identified.
OK, one of the cables in the earth bar could be an earth, possibly a TT install with a buried rod and plastered over cable.
Any other ideas where it could have got the earth from?

Flat and old installation rings a bell! I've come across a main earth connected to the main water pipe at the header tank, this pipe entered the loft space from the stair well, and was in the top flat of a 2 storey building with a TN-S supply! There was no bonding to Gas or Water pipe entering the property at that time, ....... there is now and there is a change to PME!

Regards
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