Andy Wade wrote:

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.


I'd say that's exceptionally low for a single 4 ft. 50 - 100 ohms is
more common, so you've clearly got very good soil.

Yup, I was quite pleasently surprised. When we moved in the *only* earth
connection was to the gas supply (also about 12 ohms), so I was
wondering what reading I would get from a rod on its own without any
contribution from the gas and water bonds. After some experimentation it
seems that close to the house any length of rod that goes more than a
few inches into the ground gets you about 12 ohms.

My workshop earth was reading about 22 ohms (probably in dryer soil with
lots of tree roots about). So I added a second rod in parallel about 14'
away to that to get it down to the same as the house.

For my workshop & shed installations I've got two 8 footers in parallel
(one of them deliberately near a soakaway) and find a consistent 7.5 to
8 ohms.

What sort of earth connection would they have at a typical substation?

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/