Grounding in desert

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440doublebuck

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Baytown, Tx
I leave at the end of the month for Afghanistan. I'm sure you all have seen the news reports of soldiers being electrocuted in improperly grounded bath houses. Never been there so i can only assume that the soil is mainly rock and sand and that a single ground rod would have more than 25 ohms of resistance what would would be the best grounding system? Ground loop of bare 4/0 around base? Given the company is willing to pay for it.
 
The loop may not be deep enough to encounter moist soil.

If you could jam a 20 ft rod straight down. Be it copper or galvanized if temporary. The main thing is you need some damp soil. Perhaps you could tale a baco and dig a large hole then sink the rods even further then the botom.

Good Luck
And Salute to you !
 
If there is a concern with people getting shocked from the plumbing, I would think bonding is the issue more than lack of properly installed ground rods.
 
081007-0641 EST

440:

You need to analyze your circuit.

Some basics:
Pure water, distilled, is a near perfect insulator. However, it can provide capacitive coupling.
Add some salts, normal tap water, and the water becomes slightly conductive, but very poor compared to copper.
Add lots of salts or acids and conductivity becomes much better, but not like copper.

Build the shower enclosure with copper, a copper floor around the shower, and copper piping. All the copper surfaces and the water coming out of the shower head are at the same potential. Thus, no shock problem within this area and while a person was in this shower the potential of the copper could be raised to 1,000,000 volts relative to earth and still no shock within the shower. You may call this a Faraday shield if you want.

So grounding an electrical system, other than the step potential of getting into this shower, is not the problem.

Thus, you have to analyze where the problem is.

If the shower floor is conductive to one side of the power source, the shower walls are insulators, the water piping is an insulator, the water has normal mineral content, and the water supply is in contact with the other side of the power source, then there can be adequate current flow thru the person taking the shower to cause electrocution.

The step potential problem needs to be considered separately.

So I believe what you need to do is use copper piping for some distance before the shower head and connect this piping to the shower enclosure, floor, and drain. This should make all these items, the showering person, and the water coming into the shower at the same potential. Basically any current flow from the power source thru the water would flow into the copper water pipe and back to the power source thru some path. You want the copper pipe and other shower components to be bonded back to the common of the power source.

My comments are extremes to to set the outer bounds. Fundamentally you want to prevent current flow thru the person in the shower which means zero voltage across the person.

25 ohm, 100 ohm, 1 ohm, and 0.001 ohm ground rods probably have no bearing on the real problem other than step potential.

.
 
Good point, from my understanding there are more permanent like facilities being constructed verses the temps where the hazard was higher. I'll know more in a few weeks.
 
I imagine they are having the same problems there as in Iraq. Ground rods are not going to keep people from getting electrocuted in the showers. The ground rods are mainly for lightning.

The problems they are having in Iraq is that they never established a neutral/ground bond, so there is no return path for fault current. I would guess the issues you will be fixing will mainly be grounding and bonding.

As for the showers, they didn't bond the copper pipes from the ones I have seen.
 
ultramegabob said:
If there is a concern with people getting shocked from the plumbing, I would think bonding is the issue more than lack of properly installed ground rods.
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I am sure there is a big hubbub over how to lower the ground resistance to insure safety. I am almost positive government engineers are writing specs thicker than the dictionary on how and what to put in the earth when in reality IMO they should drive a rod or two and BOND, BOND, BOND.
 
From what I am seeing here in Iraq, its all bonding, and crappy workmanship. We have checked ground rods with a clamp-on, and surprisingly we are seeing anywhere between 6-11 ohms.
 
440doublebuck said:
... Never been there so i can only assume that the soil is mainly rock and sand and that a single ground rod would have more than 25 ohms of resistance what would would be the best grounding system? Ground loop of bare 4/0 around base? Given the company is willing to pay for it.
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fourfourOh -
As has been said, grounding may not help the perceived problem.

Still, for grounding methods, I'd get a copy of Soares Grounding and take it with you. Ufer did most of his work in the desert - that probably will apply.

carl
 
mxstar211 said:
From what I am seeing here in Iraq, its all bonding, and crappy workmanship. We have checked ground rods with a clamp-on, and surprisingly we are seeing anywhere between 6-11 ohms.
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If you are getting 6 - 11 ohms in the desert you should be smiling. The ground loops or rods are not the problem. As stated bond well and check the circuits. Grounding is also very important. EGC can do wonders if the circuit tries to fault but if the EGC is not connected you could have some real safety issues and faults going thru people rather than back to the source.
 
Dennis Alwon said:
If you are getting 6 - 11 ohms in the desert you should be smiling. The ground loops or rods are not the problem. As stated bond well and check the circuits. Grounding is also very important. EGC can do wonders if the circuit tries to fault but if the EGC is not connected you could have some real safety issues and faults going thru people rather than back to the source.
Click to expand...

Yes, we were pretty shocked with 6-11 ohms, but I am just here inspecting contractors work. As for the bonding issues we are seeing, usually there is no main bonding jumper. If they did install one, it is way undersized. Such as 35mm^2 main bonding jumper for a 630 Amp main breaker.
 
mxstar211 said:
Yes, we were pretty shocked with 6-11 ohms, but I am just here inspecting contractors work. As for the bonding issues we are seeing, usually there is no main bonding jumper. If they did install one, it is way undersized. Such as 35mm^2 main bonding jumper for a 630 Amp main breaker.
Click to expand...

This is a problem and they will continue to be shocked, literally!

The bonding jumper completes the circuit for a short to route through the neutral and to the source "XO". Without the bonding jumper fault current does not have an effective path to source to open circuits. Fault current is not trying to return to earth it is trying to return to its source. The earth is not an effective ground fault path.

An earth ground can be missed in premises wiring and the system will still function safely, but a bonding jumper cannot.

I am curious how you check ohms to earth with a clamp-on (amp meter)? Normally the earth connection to the electrode is measured at interval distances away from the electrode like 25', 50', & 75'. A ground [rod] tester is an instrument that uses dc to measure resistance from a connection at the electrode through earth to test electrodes at specific distances.
 
tryinghard-

We were not using a clamp-on ammeter, we were using a clamp-on ground resistance tester.

dereckcbc-

I totally agree with you that it is a bonding issue, not a grounding (earthing) issue.
 
mxstar211 said:
tryinghard-

We were not using a clamp-on ammeter, we were using a clamp-on ground resistance tester.

dereckcbc-

I totally agree with you that it is a bonding issue, not a grounding (earthing) issue.
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Kool, I'm not familiar with a clamp-on ground resistance tester.
 
fault protection

fault protection

440,
Additionally to a good EGC system that is effectively Bonded back to the energy source, using GFCI protection is needed. I stress this in any book I publish and emphasize a quality installation. Bonding impedances are a factor due to variables of wiring size-distance and interfacing metal parts that can be flawed by rust, corrosion and inadequate surface cleaning methods. rbj
 
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081009-1237 EST

tryinghard:

An assumption that I do not believe is generally presented is the following:

A clamp on ground resistance measurement is based on an induced current into a closed loop and measurement of that current. To induce a current you need a closed conductive loop. This closed loop and where it is located is the assumption to which I am referring.

If you put a single ground rod out in the middle of a field with no wire connecting the rod to somewhere, then you do not have a closed loop, and no current flows and you do not get a measurement of the resistance of the rod to earth (ground).

Next consider a residence that is supplied by a pole transformer with no ground rod at the pole and the transformer only terminates at this one residence. The supply neutral only connects to earth thru the ground rod at the service entrance. Still no closed loop thru the ground rod.

Next connect the pole neutral to a ground rod at the pole and maybe in many other backyards also thru other ground rods that are all connected together by a common neutral. Now we have a closed path with a combined resistance to earth much lower than the one rod we are going to test. In this case the clamp on resistance gage may give a useful reading.

This gage will use a frequency of excitation uncorrelated with the line frequency so that any ground currents from the power system won't affect the resistance measurement.

In the fall of potential method a current injection rod is used at some distance from the rod under test and that is how the closed path is supplied for this measurement.

.
 
tryinghard said:
Kool, I'm not familiar with a clamp-on ground resistance tester.
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