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Topic Title: Trouble with a rod imedance reading
Topic Summary: My 3 lead meter strugling
Created On: 06 May 2010 11:07 PM
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 06 May 2010 11:07 PM
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ady1

Posts: 766
Joined: 19 April 2005

Hi
I was working on a rewire in France and the only supply to the house was a temporary entention lead from a neighbours house 100 metres away. Whilst my temp voltage was ok at 232v my meter didn't see its earth so could not perform any kind of earth loop...
I needed to test my house rod, but again - using my temp L&N and my rod to earth, it was not allowing me to take the reading.
So i cranked up my generator, but that too is of TT arrangement. I tried L&N from the generator and my house rod to earth - still no good.
Over there, the EDF only use an earth megger, but as i very rarely do any TT work, i don't have one.
BTW. Again, over there, the EDF only connect when a dead test has been performed on the whole installation for a 'certificate de conform' independant test.
That said ... any suggestions - i need to test that rod, because its very dry out there and they want to see around the 50 ohms mark.
Regards
Ady

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Resistance is futile.
 07 May 2010 10:08 AM
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sparkyali

Posts: 7
Joined: 26 October 2007

hi ady,
i also work in france and have this issue from time to time, i don't see how EDF can expect you can perform an earth loop test without a supply?
maybe EDF just want insulation resistance etc before they hook you up.


i have a tester i got from REXEL made buy metrix MX435D that does all the tests required for the normes. it came with a probe kit for testing the earth prior to choosing a spot for the stake. this allows you to test the earth rod resistance without a supply.

if you only have loop impedence tester can you just take the temp supply you have with out the earth and connect the rod in it's place? you normaly have the removable plate on the earth rod connection so you can test the rod without getting a false reading from plumbing pipes etc. i think you should get a reading.

you won't get a reading from the genset unless the windings are L-N with the neutral/earth point staked at he genset as well. i would just run an earth cable with the supply for the genset and connect the earth directly to the distribution board. then make sure the genset windings are configured L-N in otherwords one side tied down to earth.

good luck
ali
 08 May 2010 10:51 PM
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ady1

Posts: 766
Joined: 19 April 2005

Hi Ali
Thanks for your reply...
Testing from the temp supply L&N whilst connecting the rod to the earth didn't work.
I also tried different combinations from my generator, i did rod my generator, but are you suggesting i should have connected my Neutral from the generator directly to my generator rod ?
Wouldn't that be like linking my neutral and earth together at my meter and connecting that to the house rod and my L to supply Live ?
Sorry for all the questions.... i'm a tad baffled with it.

BTW what do you think to their push fit connectors for inside their junction boxes... I love em

Au revoir

Ady

-------------------------
Resistance is futile.
 08 May 2010 11:18 PM
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John Peckham

Posts: 7382
Joined: 23 April 2005

Your loop tester is probaly aborting the test due to the high earth loop impedance. You need a 3 or 4 wire earth resistance tester to get your earth electrode resistance. Using your generator will not help as you would be measuring the impedance of the generator winding.

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John Peckham

http://www.astutetechnicalservices.co.uk/
 08 May 2010 11:36 PM
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alancapon

Posts: 5746
Joined: 27 December 2005

I agree with John here. You need the correct tester to enable you to carry out a three-lead or four-lead measurement of the earth rod resistance.

Regards,

Alan.
 09 May 2010 11:47 AM
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ady1

Posts: 766
Joined: 19 April 2005

Well that's good enough for men gent's... I will beg, steal or borrow one
It was certainly worth a try with my loop tester.

Regards
Ady

-------------------------
Resistance is futile.
 09 May 2010 11:51 AM
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Avatar for Testit.
Testit

Posts: 2962
Joined: 06 August 2007

buy yourself a nice fluke 1653 that will do it all for you... one tool for the job....

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