Dapo,
I was under the impression, that if you preformed an Earth-loop test at the switch-board and at each "Point", this would give you a reasonable idea of your Earthing resistance, anything over about 0.75ohm, would have me worried, but in a reasonably new installation, you should be getting readings of 0.25-0.4ohm.
We haven't used the old Earth Continuity test, since the Earth-Loop test, became a means of compliance, in the 2000 Amendment to the Regs, in NZ.
Hope that this helps!. [Linked Image]

[This message has been edited by Trumpy (edited 03-24-2003).]