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Earth Electrode Concern.

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I was working in a large back garden today. The garden shed was connected to an old caravan supply (caravan gone) and the underground S.W.A. cable from the house had been  converted to TT earthing originally for the caravan and now for the shed sockets and lighting. As an earth electrode somebody had used a length of  10mm galvanised threaded rod (studding). What are your views about its suitability please?


Z.
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    RE the 10mm dia threaded galvanised steel rod.


    In manufacture, is that a 10mm galvanised steel rod which has then been threaded and thus removed the galvanising off the threads, or a 10mm steel threaded stud bar which has then been threaded?

    Clive
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    new rods in dry ground are always a bit loose, joins or not as the hammering gives them a radial vibration, and you can speed them up in reaching a lower Ze a bit by watering them in.

    There are various ways the beer disposal squad may do this if they have been busy trenching and hammering  in the sun after a pub lunch, the finer details rather depend who is watching.

    Nowadays the SDS drill makes it easy in some soils, and in other cases if you have water available at pressure, then a water drill is better. In really hard substrates a flat or near flat electrode or a doped concrete slab may be considered. If you are in a hurry, and moving on tomorrow, then lay the rod flat on the soft and park the truck with the tyres over it.
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    I tried watering a 3.6 metre rod I had knocked in, it went from 27.69 ohms to 25.05 ohms after having a hose pipe on it until the pit flooded. 

    So that is three sections of rods and wet, one section on it own was 584 ohms.

    Depth makes more difference than water. 

    Andy
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    Sparkingchip:

    Depth makes more difference than water. 




    Not if the deepest part is saturated. Adding water would not be expected to change things to any great extent.

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    AncientMariner:

    RE the 10mm dia threaded galvanised steel rod.


    In manufacture, is that a 10mm galvanised steel rod which has then been threaded and thus removed the galvanising off the threads, or a 10mm steel threaded stud bar which has then been threaded?

    Clive





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    How about a length of steel conduit? ?
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    I have always thought that the copper plating on steel earth rods is just to bling them up a bit more than galvanising or other types of plating.


    Andy B.
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    25.05 ohms after having a hose pipe on it until the pit flooded. 

    So that is three sections of rods and wet, one section on it own was 584 ohms.

    Depth makes more difference than water. 

    Andy 




    That will be one of those where the text book simplifying assumption the ground conductivity is uniform is clearly so untrue as to be utterly risable. I imagine if you were to dig a trench you would see clear strata of different materials and varying moisture  content, with something deeper down that is much more conductive covered by an almost insulating skin. Is the top soil light and sandy or very pebbly by chance,  sitting on clay ?


    I recall being surprised by the high surface conductivity of Essex clay  at a scout event with lots of earth rods when compared to Hampshire's finest gravelly loam with which I am more familiar.

    This year of course after almost 4 years of planning to do the next one, it has had to be cancelled due to this virus business.


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    Chris Pearson:

    How about a length of steel conduit? ?




    Yep Chris, I have seen that too, as well as galvanised water pipe used as an earthing rod. The water pipe survives well.


    Z.

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    With increased depth a rod gains length and surface area, as well as the depth, which is more beneficial than temporary solutions such as a bucket of water.


    Andy Betteridge.

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