Earth Rod Resistance is high

[weston]

Hello All,

I hope somebody can give me some guidance.
I have an installation that is a TT system, the area is very sandy, down the hill from the distribution board is a lake, approx 70 Meters away. The rise is about 10 metres from the lake to the level of the DB.
Next to the DB enclosure I have installed an earth rod 5/8 extendable, this is 3M deep in the ground, reading 612 ohm.
I have installed 9 x 1.2M (11M approx) 5/8 rods straight down approx 5M from DB enclosure, reading 658 ohm.
I have installed 3 lots of 3 x 1.2M (3.6M) 5/8 rods stright down at a distance of 3M apart in a triangle arrangement down at the lake level, reading 512 ohm.
I can't seem to get the reading down low enough.

Any ideas before I install enough rods to raise the copper and steel content of the area.

 

[Guest123]

Earth Testers - Earth Resistance Test Kits

 

[Engineer54]

Sounds as if you driving into the worst type of sand, ....Washed sand that have little to no salt sulphates chlorides or minerals.... not that you would want too much sulphates and chlorides...lol!!

If after checking that your test equipment is confirmed good, then other than keep banging in rods, your only other courses are, ....Straight Chemical enhancement, Bore drilling, followed by chemically enhanced Bentonite mortar, Bore drilling followed by enhanced Conductive Portland mortar (very high carbon dust/particle content)...


Personally, i don't think i've ever had readings on any of my projects, that are as high as your reading. What may be happening is, (if there are other close by underground cables) your getting erroneous reading due to electrical noise etc... Any chance of you borrowing an earth tester, or at the very least another MFT to check your own tester against....