Ze result different from a few months ago.

[schoe]

Just carried out a ze on a tt istallation and got a reading of 156 m ohms, carried the same test out a few months before and got 132 m ohms, the zs results were slightly higher as well! Could this be due to the changing conditions of the weather as to we're the earth rod is placed.

Thanks chris

 

[Octopus]

Yes. Think temperature and the amount of moisture in the soil. TT in the sahara wouldn't be too good

 

[Engineer54]

Just carried out a ze on a tt istallation and got a reading of 156 m ohms, carried the same test out a few months before and got 132 m ohms, the zs results were slightly higher as well! Could this be due to the changing conditions of the weather as to we're the earth rod is placed. Thanks chris

What earth rod(s) did you use, ...a single 3/8'' non extendable rod, or a single 5/8'' extendable rod?? And how far from the house external wall did you locate your rod??

Yes. Think temperature and the amount of moisture in the soil. TT in the Sahara wouldn't be too good

Not exactly correct, i have installed 9 TT systems on a multi location project in Libya, one being 900Km from the coast into the Sahara desert. The worst value obtained was from memory being 0.87 ohm or thereabouts. But then we were using proper 3/4'' 3.2 metre copper clad rods. Just needed to use enhancement mortar, in this case Bentonite!! The Sand in the Sahara is literary full of sulphates and chlorides, so quite conductive in it's own right. Furthest 2 installation didn't get any annual rainfall, so irrigation systems was also installed to maintain earth field moisture content...


Also susceptible areas of corrosion to the large pipe line, were protected with passive cathodic protection using magnesium strings, also with Bentonite mortar. Results were very positive to say the least!! Not all sands are the same!! lol!!

 

[Marvo]

If it was a new rod installation I'd expect the impedance to improve steadily over the fist year as the soil around the rod settles. Also I'd expect a better result in winter due to higher soil moisture content. If your impedance has increased over the last few months I'd earmark the rod for regular monitoring to try to establish it's stability. If you're in doubt it hopefully isn't too much of a job to add a 2.3 meter extension to it and whack it in deeper.

 

[FAA Greenie]

You could probably go back tomorrow and get a different result buddy.

 

[MarkieSparkie]

... TT in the sahara wouldn't be too good

Sahara sand is actually quite conductive due to the dissolved minerals and salts it contains. Granite areas in Cornwall are a real challenge. Certain limestone areas in Dorset are tricky also, the last installation we did for MOD required a copper mat the size of a football pitch to meet the required specification, because the soil depth was so shallow.

 

[Engineer54]

Sahara sand is actually quite conductive due to the dissolved minerals and salts it contains. Granite areas in Cornwall are a real challenge. Certain limestone areas in Dorset are tricky also, the last installation we did for MOD required a copper mat the size of a football pitch to meet the required specification, because the soil depth was so shallow.

And very expensive too!!

Limestone areas depend on whether the limestone is fractured limestone or not. If it's of the fractured type then bore holes/Bentonite would have been a far better solution, and costs greatly reduced too!! lol!!

 

[moose]

An old Spark once told me they used to wee on them to get a better reading, not something i could do ROFL....

 

[electricpawn]

P on the ground..that should lower it !!!

 

[Clive P]

Hi,

Just to throw a bit more into the mix. I have used Bentonite on a number of occasions as E54's post where the soil resitivity has been very low; and always used Austentitic rods ( Stainless coated rods 12mm dia ) in the presence of Cathodic Protection. One to chew over.

Regards