I have a home with separate flat on the grounds. Our system, in South Africa, has 230V live and neutral, supplied by the national grid operator through a distribution board, via isolator. It then goes via the earth leakage detection isolator to various circuits. We have a 4 ft earth spike outside the main building, driven into the ground, to which all the earth connections of the building are connected.

I extended and added a flat, supplying it using an 80A capable armour cable from the main house board. The shielding and earth wire for the armour cable is connected to earth at the main house distribution board bar and the flat distribution board bar to supply earth to the flat.

I want to add an earth spike at the flat and connect it to the earth bar in the flat's distribution board for redundancy. Is this a good or a bad idea? I asked on another forum and someone suggested it was bad... going into an explanation about ground loops and huge current... I gathered he is not an electrical engineer so I thought I'd ask here before I make any decisions.

Thanks in advance!

  • Where are neutral and earth bonded? – Jeroen3 Aug 12 '18 at 10:50
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    Assuming that the South African system maintains separate "earth" and "neutral" wires, it should be fine to bond "earth" to a ground spike at additional points. What you must NOT do is create any additional bonds between earth and neutral, which would create problems for the leakage detector. – Dave Tweed Aug 12 '18 at 11:49
  • Is the flat fed TN-C (combined protective earth & neutral) or TN-S (separate protective earth and neutral)? – ThreePhaseEel Aug 12 '18 at 11:58
  • @ThreePhaseEel It's fed separate protective earth and neutral I assume - see my other comments. – wedwo Aug 12 '18 at 14:44
  • @Dave Tweed, Thanks for that feedback, that's my assumption too. From my understanding, in South African homes, earth is there to provide a path to ground for stray induction current and of course protection from faults (short to appliance chassis / ground) on either the live or neutral circuits. Either will trip the earth leakage isolator. – wedwo Aug 12 '18 at 14:45

Go ahead and put the second earth electrode in

Since your neutral is isolated from earth at the flat, you can safely put an earth electrode at the flat and wire it to the earthing terminal bar at the flat's distribution board. (This works irrespective of whether your distribution system is TN-C-S, TN-S, or TT.)

There are no concerns about ground loops here since the only currents that flow on earth wires are fault currents, and the ground itself is too poor of a conductor to carry those fault currents.

  • Make sure you test the earth leakage detectors. – Jeroen3 Aug 13 '18 at 5:45
  • Thanks ThreePhaseEel. @Jeroen3 agree, will test earth leakage. Cheers! – wedwo Aug 13 '18 at 17:35

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