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Topic Title: Zs rises after bringing down the Ze?
Topic Summary: Tired brain not working today.
Created On: 10 March 2010 04:44 PM
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 10 March 2010 04:44 PM
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sivoodoo

Posts: 85
Joined: 21 September 2008

Hi all,

Domestic property rewire.

Kitchen ring - socket outlet, measured Zs of 14.6

checked the Ze at the board and way up at 580.

Banged in an earth spike, Ze now down to 160

Checked Zs at same socket outlet and it measured 80.5

???

Why would this occur?

Just got home not had time to think cleary, any pointers please.

Kitchen ring
r1 = 035
rn= 0.34
r2 = .54

-------------------------
Regards

Si Micklewright. BSc.
 10 March 2010 04:55 PM
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AJJewsbury

Posts: 11686
Joined: 13 August 2003

Disturbed some of the bonding that was providing some of the original parallel paths to earth? Or left something disconnected that has a N-PE fault?

A TT installation I presume.

- Andy.
 10 March 2010 05:00 PM
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sivoodoo

Posts: 85
Joined: 21 September 2008

Yes TT system, though did look like a TN-S at first glance, G/Y ribbon cable from MET clamped to incoming supply.
Cant thnk what the hell was disturbed, but there is a plasterer on site going round scrounging every bit of copper he can find!!!

Back in the morning, to carry out continuity on all the protective conductors, wonder if he has had away with the middle sections!!

Thanks AJ.
Simon.

-------------------------
Regards

Si Micklewright. BSc.
 10 March 2010 05:01 PM
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daveparry1

Posts: 6328
Joined: 04 July 2007

I also reckon some bonding has gone awol for some reason or another!
 10 March 2010 07:48 PM
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jcm256

Posts: 1921
Joined: 01 April 2006

Interested in TT, what way did you measure the earth electrode, did you have the crocks on the mains side of the RCD and the earth probe directly on to the earth electrode cable that was disconnected from the earth bar, was it a high current loop test at 20 or 25 A ?. Was it AC current loop tester or a DC current tester? How did you measure the earth loop impedance at the socket, was it by switching the loop tester to a current below the RCD trip threshold i.e. 15mA. Why am asking these enumerated questions (which may seem as a lot of balls) is to determine your testing methods. it is possible that there is a simple explanation for your unusual readings, would be grateful when you further investigate to post what it is.
Regards
jcm
 10 March 2010 09:15 PM
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Avatar for 1652.
1652

Posts: 348
Joined: 22 March 2007

Knackered face plate, Poor connections/switch on the face plate.

Had a job 2 weeks ago guy getting elecric shock from equipment plugged into face plate, no shock from the other socket on the double socket face plate.

Internal fault within the face plate meant the earth was not connected to one of the socket outlets hence the earth on the plugged in equipmet was rising to 120V AC.
 10 March 2010 09:35 PM
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sivoodoo

Posts: 85
Joined: 21 September 2008

Jcm,thanks for the comprehensive reply.

I shall carry out all tests again in the morning and report back.

Thank you all for now.

-------------------------
Regards

Si Micklewright. BSc.
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