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Discuss Main Bonding issue. in the Electrical Forum area at

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  1. wcampbell

    wcampbell Guest

    Hi all.

    I 'm getting 1.58ohms continuity on this main 10mm Earth bonding to water. The bond continues up to the flat upstairs and who ever did the work threw in 12" length of 4mm earth for good measure. Am I missing something or is this a case of new E Bond. Fitted a new clamp but did little to reduce the figures.

    Any thoughts please.


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  2. tony mc

    tony mc Electrician's Arms

    I think you have answered your own question in that the figure is too high and if it was 10 mm cable you would be looking at a lenth of 863meters.

    You have already found a bodge job with the 4mm so IMO put it right by installing a new cable.
  3. Welchyboy

    Welchyboy Guest

    Even 4mm should give u a better reading than that, replace it!
  4. Archy Styrigg

    Archy Styrigg Forum Mentor

    What a mess, hope that's the before picture!
    Put in new separate 10mil bonds from where the water enters each flat to the respective METs.
    Scrub the pipes to shinyness before fitting the clamp then test from the pipe to MET, what I was taught.
    And use ring crimps.
  5. Engineer54

    Engineer54 Guest

    Disconnect this cable to the upstairs flat, it should not be leaving your equipotential zone or be influenced/connected to/by another equipotential zone. As others have suggested, if required replace the bonding conductor back to the MET.

    Just to be certain, why not check this water service, to see if it is an extraneous earth!!! might just be a section in plastic!!!
  6. Mfctitch

    Mfctitch Regular EF Member

    Southend on Sea

    Not sure if this comment helps but looking at the photo, it looks like the mains water supply is plastic.
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  7. wcampbell

    wcampbell Guest

    Thanks all.

    The pipe work is all metal apart from main incomer. Will replace main bond this coming week.
  8. Engineer54

    Engineer54 Guest

    Then you need to do an IR test from the MET to the metal side of the water service pipe. If it's under 23000 Ohms (23 KOhms) it requires bonding, if over, then it's not an extraneous earth, and no bonding is required. But you'll still need to isolate/remove that bonding cable that is going to, or coming from the flat above....
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