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Thread: Missing or hidden earth spike

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    Missing or hidden earth spike

    Here's a fun one. For a house built in the mid seventies in Cape Town no sign of an earth spike (or associated cables) can be found.

    Now it's possible that it was removed or covered over during subsequent additions, alternatively it was never installed.

    Has anyone come across anything like this? E.g. was it a common practice to not add earth spikes in those days? Or is removing them common place?

    I know those questions call for speculation so I'll provide some alternative questions for those who prefer not to speculate:

    Have standards with regards to providing an earth to a property changed since the mid seventies?

    Are there any acceptable (read: code compliant and effective) alternatives to using an earth spike?


    And yes I find this sort of thing fascinating.

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    Diamond Member AndyD's Avatar
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    Quote Originally Posted by smitty View Post
    Here's a fun one. For a house built in the mid seventies in Cape Town no sign of an earth spike (or associated cables) can be found.

    Now it's possible that it was removed or covered over during subsequent additions, alternatively it was never installed.

    Has anyone come across anything like this? E.g. was it a common practice to not add earth spikes in those days? Or is removing them common place?
    I don't do domestic electrics but in my very limited experience even the old Cape Town houses I've seen all had an earth spike. I'd speculate it might be more likely to have been a steel one that corroded and was never replaced.


    Quote Originally Posted by smitty View Post
    Have standards with regards to providing an earth to a property changed since the mid seventies?

    Are there any acceptable (read: code compliant and effective) alternatives to using an earth spike?


    And yes I find this sort of thing fascinating.
    Not sure about the regs in the 70's, I'm not that old. There is an earthing arrangement (TN-C) that is no longer permitted. In TN-C installations there was no separate earth wire (CPC) and in some installations the neutral and earth was linked in the back of each socket. The problem was if the main supply neutral ever became open circuit or disconnected then the entire earthing system of the premises and all appliances became live and killed the users of the installation. It was also before the advent of earth leakage protection so likelyhood of death by neutral fault was pretty high so this type of earthing arrangement quickly became unpopular. I've only ever seen one installation that was configured this way so it's unlikely your house has this system.

    TN-C-S earthing which is very common nowadays is also prone to this type of fault although it's less likely to occur than with TN-C but this is why every property should have its own earth spike and usually the council or Eskom have numerous earth spikes along the length of their supply cable. This system of many earth spikes is called PME.
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    I seem to recall my old house that I grew up in the Southern Suburbs had that copper cable, but it was attached to the downpipe/external metal air vent.
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    Quote Originally Posted by AndyD View Post
    I don't do domestic electrics but in my very limited experience even the old Cape Town houses I've seen all had an earth spike. I'd speculate it might be more likely to have been a steel one that corroded and was never replaced.


    Not sure about the regs in the 70's, I'm not that old. There is an earthing arrangement (TN-C) that is no longer permitted. In TN-C installations there was no separate earth wire (CPC) and in some installations the neutral and earth was linked in the back of each socket. The problem was if the main supply neutral ever became open circuit or disconnected then the entire earthing system of the premises and all appliances became live and killed the users of the installation. It was also before the advent of earth leakage protection so likelyhood of death by neutral fault was pretty high so this type of earthing arrangement quickly became unpopular. I've only ever seen one installation that was configured this way so it's unlikely your house has this system.

    TN-C-S earthing which is very common nowadays is also prone to this type of fault although it's less likely to occur than with TN-C but this is why every property should have its own earth spike and usually the council or Eskom have numerous earth spikes along the length of their supply cable. This system of many earth spikes is called PME.
    You may not do domestics but you're still a fountain of knowledge! Even though you're not that old. :-)

    Ja it could easily have rusted away over the four decades since it was installed. Looks like R2000 to have one installed and connected...

    I also don't think this is a TN-C. The installation seems a bit more modern than that and the electrician didn't mention anything of the sort. It's obviously not that modern an install either because the 20 mA earth leakage breaker tripped when it was tested at that rating (every circuit - yes it was a thorough CoC inspection). I recall that detail because the electrician specifically mentioned it was tested at 20 mA because it is rated at that rather than 25 mA which (most) newer ones are rated at.

    I also watched while the distribution board was being inspected. There are a lot of earth cables from the various circuits all being tied (screwed in) to a central point on the metal DB casing.

    Funnily enough while the plug points all passed their earthing tests there where quite a few earth faults picked up on lights fittings and switches. When inspecting one of those light fittings that didn't have a (good) earth reading it was found to be connected to the supplied earth wire in addition to live and neutral.

    I suspect some of this may have to do with the original part of the house using metal conduit as the earth while the newer part is using on twin and earth / surfix. Bonding the metal conduits together with copper strap was mentioned as the fix for that.

    I'm not sure why some of the lights connected to the twin an earth are not getting a good earth reading. Perhaps a lose connection somewhere in a junction box or at the DB.

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    The commonly used earth leakage breakers in houses are 30mA rated but they often trip anywhere above 20mA on a test (usually around 25mA). If the steel conduit was used as the earth for the circuits it often gives poor test results especially near the coast due to corrosion. Usually pulling a new earth wire in is the answer but copper straps across the joints would also work.
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