Andy Wade wrote:

If you achieve the OSG recommendation of 200 ohms in normal conditions
then I really don't think you'll need to worry too much about the ground
drying out or freezing in extreme weather, unless you're on very rocky
ground (literally).

If a 100 mA is involved the figures become 500 and 250 ohms, so the
margin is reduced somewhat. IME (which is limited to chalky and clayey
soils) you're unlikely to have any worries if an 8 ft earth rod is used.

From the measurements I have taken from my installation (heavy clay
soil) a 4' rod will give a resoanably consistent 11 - 13 ohms year round.


--
Cheers,

John.

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