Measuring the earth rod resistance with an efli tester

Discussion in 'Electrics UK' started by TONY144, 6 Apr 2008.

  1. TONY144

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    does anyone know please if it is possible to test the value of the earth rod resistance Ra I believe using a 3 lead tester on an efli robin tester because the niceic book and other literature i have seen only shows a 2 lead tester on phase and earth rod ? any suggestions

    Thankyou :confused:
     
  2. sparkybird

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    yes, IIRC look in Guidance Note 3 (testing and inspection) at method 2 for Ra testing.

    Someone has nicked my copy or else I'd tell you the page!

    SB
     
  3. TONY144

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    thanks will look

    cheers

    Tony
     
  4. Spark123

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    Put the black test lead on Neutral ;)
     
  5. TONY144

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    That will give the ze reading i believe and not the resitance value of the earth electrode but correct me if i am wrong
     
  6. Spark123

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    What is the Ze in a TT system?
    The black (neutral) is required to power the instrument and in some instances such as DLOC for the electronics to lock the RCD.
     
  7. plugwash

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    Assuming you measure with main bonding disconnected it is the output imedanace of the suppply transformer plus the impedance of your live supply condutor plus the impedance of your electrode plus the impedance of your suppliers electode.

    In practice the impedance of your rod is likely to be much higher than any of the other things mentioned above and it is normal to use the Ze measurement as a conservative estimate of the impedance of your rod.

    testing earth rod resistance seperately requires a different type of tester and several temporary test electrodes but there is rarely any reason to do it.
     
  8. Spark123

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    Yep, what is the difference between a Ze measured with a 3 wire efli tester and a Ze measured with a 2 wire efli tester?
     
  9. TONY144

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    Thanks lads between you all i now have the answer to my initial question.
     

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