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Lightning electrodes

lyledunn

A relatively small parish church has 8 down conductors connected to rod electrodes. Each electrode measured separately ranged from 215 ohms to 12 ohms with the overall value being around 8 ohms. Now I am aware that the overall value should be less than 10 and that each individual electrode should be no more than 8x10. We have one at 215 and one at 135, the others meeting that requirement. It is easy for me to advise that the system does not meet code but I do not have the expertise to assess the implications of the situation. I would appreciate your opinion. 

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    Thanks Mike. Yes it is a complex subject. I rather think that is the attraction for me but unfortunately reports, plans, invoices, quotations and general day to day business prevent me from any deeper diving. I am glad that this forum has people like you who are infinitely more clued-in than me!

    I have test instruments that allow the FOP and stakeless methods, as well, of course, as the standard earth loop. Just out of interest, we used all three with results being fairly similar. Comparing the FOP result with the loop results we figured that the DNO connection to earth was around two ohms or below. 
    So our results show an electrode well outside acceptable as far as code recommendations are concerned but the overall resistance below that required 10 ohm value. As David Z indicated, the resistance may only be a lesser component in what is a non-linear arrangement. 
    With the greatest respect to the LPS contractors, I doubt whether they could offer an answer as to the seriousness of the situation other than to say it’s outside code and here’s a quote for fixing it. 
     

     

     

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  • 0

    Thanks Mike. Yes it is a complex subject. I rather think that is the attraction for me but unfortunately reports, plans, invoices, quotations and general day to day business prevent me from any deeper diving. I am glad that this forum has people like you who are infinitely more clued-in than me!

    I have test instruments that allow the FOP and stakeless methods, as well, of course, as the standard earth loop. Just out of interest, we used all three with results being fairly similar. Comparing the FOP result with the loop results we figured that the DNO connection to earth was around two ohms or below. 
    So our results show an electrode well outside acceptable as far as code recommendations are concerned but the overall resistance below that required 10 ohm value. As David Z indicated, the resistance may only be a lesser component in what is a non-linear arrangement. 
    With the greatest respect to the LPS contractors, I doubt whether they could offer an answer as to the seriousness of the situation other than to say it’s outside code and here’s a quote for fixing it. 
     

     

     

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