Brian Gaff wrote:

Also of course when dealing with such low impedance systems the way you
connect them together will matter as well. some very thick copper?
Brian

I don't think domestic earth systems are as low impedance as one might
think. Someone said between 10ohms and 150ohms, and these are the sort
of figures attainable without burying huge amounts of copper. Conductor
diameter is more governed by possible fault currents than anything else.
Also mechanical strength may be relevant if exposed. You won't go far
wrong in a house using 16mm^2 and that may be unnecessarily big.

There are, of course, regulations you can look up if necessary. But
huge bus bars are probably not useful.

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Roger Hayter