Why did this ground rod fail?

[gimbo2]

Forget all the fancy meters and metal types.

We had the same problem or similar years ago.

Easy fix.

Piece of 3/4" galv pipe 6'-0" long ,bottom "pinched closed", drill 2 X 1/8" holes an inch up from the bottom.

Get bloody big heavy hammer and drive it into the ground until about 4" above the ground. Use 1 or 2 good strong hose clips and clamp your house earth wire to it.

Now the "Trick" fill the galv pipe with old engine oil. Top it up once a year. NEVER had a problem, and yes we also earth the steel roof through this pipe so for sure its earthed some lightening over the years and it is still like new.

Old ways are many times better than the so called "High Tech" ways, they are proven.

Grumps

[Crossy]

NICE meter, you obviously didn't buy that in Thailand LOL.

If you have someone in the UK that can post it to you there are some pretty good Ebay deals on "16th Edition" testers, like this one http://www.ebay.co.uk/itm/Robin-KTS1630-Multi-Tester/121473539425?_trksid=p2045573.c100033.m2042&_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20131017132637%26meid%3Dcd9f8f94be7b4bf9a3eb5ac29b85a9ec%26pid%3D100033%26prg%3D20131017132637%26rk%3D2%26rkt%3D4%26sd%3D321566086446

Mine is w-a-y out of calibration but is also w-a-y better than the usual 'bang' test performed by our local sparks.

[MW72]

You need a resistance of less than 10 ohms. The reading will depend on the type of earth as well as the rod you use. Some types of earth just don't conduct well. If you can't get less than 10 ohms you can buy an earth mat which will give you a much larger surface area for any charge to go to ground. Copper is the best conductor.

[Crossy]

You need a resistance of less than 10 ohms. The reading will depend on the type of earth as well as the rod you use. Some types of earth just don't conduct well. If you can't get less than 10 ohms you can buy an earth mat which will give you a much larger surface area for any charge to go to ground. Copper is the best conductor.

Why if you have a 30mA RCD? (required for new installations in Thailand)

Without an RCD a 10 ohm ground (L-E short) isn't going to interest a 20A breaker and the 40A on your water heater won't bother waking up.

Any idea where to buy an earth mat in Thailand?

Remember we're not in Kansas Houston any more.

[ksamuiguy]

would be interesting to know what you find if you dig the old rod up.

If a lighting strike there may be "Sprites" that have formed in the sand/soil (irregular shaped glass type beads) caused by the arc fusing the sand.

[Crossy]

Bu99er, I'm going to have to actually dig the thing up

[RichCor]

Bu99er, I'm going to have to actually dig the thing up

Yep. Digging it up would possibly illuminate what happened to it. I'm certainly curious.

Was only a small section affected or was the whole thing leached? Acid, galvanic, cathodic corrosion ...

Gone in 2 years?? Hope you don't have any other buried metal conduits.

Would be funny if you had to put in place a set of sacrificial magnesium or zinc anodes and set up a direct current between the inert anode and your structure to ensure the structure does not produce electrons. Everyone would think you were daft. Well, more daft than usual.

[RigPig]

Bu99er, I'm going to have to actually dig the thing up

Actually you don't have to dig it up Crossy, just get 2 substantial sticks and tie the (fix) at the top with a small cross over, then use a crow bar (or another substantial sick) and use it as a lever, tying the end of it to the rod and levering it out. When I was young in Aus we used to do this to pull what they call "star" pickets for fencing out of the ground. I have used this method for removing earth rods too, you will be surprised how easy it is to pull it out. If you need a diagram (not sure how good my explanation is) PM me and I will draw a picture and email it to you.

Hope this helps...

[steve73]

I've also had problems with a copper clad earth rod corroding - I've jut replace one with a 2m stainless steel pipe....which I thought would be better than galvanised.... (I'm very close to the sea, so it's into damp, saline sand)

Anyone able to confirm if I am correct in this....or would I be better sticking to galvanised steel?

[ksamuiguy]

Stainless Steel is a very poor electrical conductor. Copper/galvanized rod best, Suppot has proper 5/8 ground rods up tp 2.4 meters long.

The key to copper is that Copper oxide conducts electric the copper oxide protects the copper from further corrosion/oxidation.

[ksamuiguy]

I have information on Earthing, Grounding and Bonding. Some requires some engineering background some is written for the Safety Conscious home user.

There are also some very informative videos and how to's on YouTube,

Just search for Earthing, Grounding and Bonding.

I believe the next thing we need to discuss is Bonding, why didn't my circuit breaker trip?

[ksamuiguy]

Things don't need to blow up, we have the devices here and they are locally available.

But Earthing, Grounding and Bonding has to be done right for them to work.

Just a question I was asked, answer "Safety Cut Breaker" it trips by measuring the current leakage between Hot and Neutral conductors, usually most here trip at 30 ma. lower trip should be used in kitchens, bathrooms and lower still in Hospitals.

You still need a good ground on your water heater even with a Safety Cut. again good informative easily understood information on YouTube.

Earthing, Grounding and Bonding work together to protect you, your family and your electrical devices.

[ksamuiguy]

Ground is a source for unwanted currents and also as a return path for main current. While earthing is done not for return path but only for protection of delicate equipments. It is an alternate low resistance path for current.

Earth is used for the safety of the human body in fault conditions while Grounding (As neutral earth) is used for the protection of equipment.

[Daffy D]

Many years ago when I was living in a shack on the beach the computer was giving out tingles. I "cured" this by connecting a wire from the computer case to a copper clad ground rod in the sand.

When I moved after about a year I tried to take the ground rod with me (cheap Charlie) but could not pull it out of the sand. I would have thought sea sand was be about the worst environment for a metal rod but it was stuck fast and I had to leave it.

"Crossy" are you shure you house is not built on a toxic waste site

Some time ago I watched as guys from the electric company were putting in a ground rod next to one of their utility poles. This rod looked like it was made from aluminum and was about 12ft long. They had to go up a ladder to hammer it into the ground.

Presumably the electric company would be using the best material for the job, so why have I never seen aluminum ground rods for sale?

[Crossy]

Aluminium is probably the worst material that you can use for a ground rod, in fact you can use pretty well anything metallic except aluminium. The problem is that, unlike copper oxide, aluminium oxide is a very good insulator.

The rod that the electric company were using was probably hot-dip galvanised, cheap and reasonably long lived.

EDIT On the subject of YouTube. There is indeed some excellent advice on YouTube, there is also plenty of incomplete, misleading or outright dangerous advice. Mr Average Joe is never going to determine which is which.

Rather than just say 'look on YouTube' please link to your recommended videos.

[topt]

This is probably two stupid questions but if you don't ask........

How can you tell if you (may) have an earth rod and if you think you have is there any way to locate it - Ie is it obvious where to start looking?

The reason I ask the latter is that most of the ground outside the house within say 5 meters of the consumer unit is concreted over. I know there are wires running under the garden somewhere as there are garden lights switched from inside the house.

[Crossy]

Ah TOPT, 64,000 Baht question.

Probably the easiest starting point is to take the lid off your distribution board (power off) and post a clear photo here (you should probably start a new thread). We should be able to get you moving in the right direction.

Concreting over the ground rod seems to be a national pastime

[Forkinhades]

BS7671 states that an earth rod measuring over 200 ohms would be deemed unstable!

However I would not be happy with anything as high as that, personally I would be looking for less than 20 ohms.

A wind up meggar for low readings, that cheered up my rather dull Sunday morning

Interesting thread, would like to know how you are going to overcome this Xy

The oil suggestion is rather intriguing.

I have both Fluke and Meggar Multi function meters, and would recommend the meggar by far for thailand. The fluke has lots of issues with 'noise' and was unable to get readings, and just give error.

[T_Dog]

Crossy, I have puzzled over your photos for a while. I have never seen steel pulled out of the ground in Thailand that had a shiny luster to it as your ground rod appears to have. Did you clean it or somehow abrade off the oxide that normally occurs so quickly here? If not, I wonder how the rust would have been pulled off it was natural corrosion.

I have a lot of experience doing lightning mitigation work for avionics equipment so have studied lightning strikes at length. With the magnitude of energies available, it would not surprise me to see sand move enough during a stroke to cause abrasion to clean your rod. Do you have any other evidence of a lightning strike to your home? Were you home at the time all the equipment failed?

[Crossy]

Well, I've spend a muddy hour or so mucking (literally) around in the bottom of our 12" deep earth pit, failed miserably to find the old rod.

I may not have gone deep enough and not knowing exactly where the rod is doesn't help.

I'll just keep a good eye on the new rod.

@T_Dog - all I did was washed the clay off the rod, I agree it's decidedly odd.

We had a direct hit last year, took off some ridge tiles and left a nice witness mark on Wifey's very expensive teak barge board. That took out quite a lot of kit but the main charge was safely conducted to deck via the building steel which is tied all the way into the piles (a side effect of having a decent contractor).

We had a recent surge which killed off less kit (invested in a job lot of quality plug in surge arrestors), no evidence of a direct hit so I suspect the neutral took it, but the main house MOV didn't appear to have been triggered which is what prompted me to check out the local grounding. The rest is now history.

EDIT I was about 4m from our distribution board when the surge occurred, there was a good solid 'pop' and both RCD's tripped but I can't see any damage.

[topt]

Ah TOPT, 64,000 Baht question.

Probably the easiest starting point is to take the lid off your distribution board (power off) and post a clear photo here (you should probably start a new thread). We should be able to get you moving in the right direction.

Concreting over the ground rod seems to be a national pastime

Thanks Crossy - I shall attempt to do that next week sometime hopefully when its not pitch black with a storm during the day!

[Pacificperson]

Crossy, having viewed your excellent home building thread and seen the flood pictures, I would guess that your soil has gone or is anaerobic and that your iron bar was attacked by the combination of organic acids and hydrogen sulphide. I think that you can see the boundary between the oxidizing and reducing zones in your photos. Iron sulphates are water soluble, which may be why you cannot find the rest of your grounding rod. Look at posts 4 and 19 again. I would think that the concrete casement will protect the iron pretty well, but it has been 40+ years since my college chemistry.

[MiKT]

Crossy

As noted in Annex A of EN 50162-2004, at the point where stray dc –current leaves the metal structure an anodic corrosion takes place at the metal/electrolyte interface resulting in oxidation (dissolution) of the metal. This dissolution follows the Faraday electrolytic law, which for a bare steel surface means that an anodic current equal to 1A dissolves 9.1 kg of steel per year.

Unless your generator is shoving out imense amounts of DC Stray Current (don't let any tall people or large 4 legged animals walk in your garden when the gen is running as the step potential would be very dangerous - which is very, very unlikely) so it's almost certain they did not put in a 2.5M earth rod for you, the amount of oxidization would be far too much for a normal rod, no matter how acidic the soil.

Looking closely at the pics, the shape of the rod does not follow the normal corrosion pattern for a long rod, why would it corrode like that unless it was close to a lot of buried steel. .Also the pointed end indicates that it was sharpend to make it easier to put into the ground. Please dig down and see what you can find and let us know.

I

[Crossy]

I can find no measurable currents, AC or DC in the new rod under normal operating conditions, day or night.

I failed to find the old rod, my wife says it was a long one and the one photo I have seems to confirm. The problem is that the earth pit is 12" deep and the top of what remains of the old rod will be about the same deeper. I don't have the tools or the enthusiasm to investigate further, it's not like I will be suing the contractor.

I will of course be monitoring the new rod, lets see what it looks like after a few months.

[wayned]

It'll be a trick to see what it looks like, say, 1 meter in the ground.

[Crossy]

It'll be a trick to see what it looks like, say, 1 meter in the ground.

I'll test it first then attempt to pull it out. If it won't come it must be OK

[IMA_FARANG]

I saw something similar in an installation when I worked in Saudi Arabia.

No trees anywhere, basically a few bushes and some large rocks scattered about in the desert.

Installation crew had done a proper ground Installation buried rod near a large rock.

During a violent thunderstorm a lightning bolt apparently hit that large rock. Evidence was a large scar and burned area on the rock.

Ground rod itself was fine, but on the oh the other end where the ground cable was connected to the common ground point for the equipment about 1 meter of ground cable was burnt to a crisp, completely melted away for the last few centimeters of the ground cable.

Only thing I could imagine was a lightning bolt hit the rock, for s second or so the best path for the charge was through the ground cable back to the equipment on line at the time ..... frying the equipment before the cable burnt out.

Weird, I know, but I saw the damage with my own eyes.

[seedy]

Don't know if allowed in LOS, but I was allowed to use a 12 inch by 12 inch bay 1/4 inch steel plate, buried one meter, instead of a groud rod in Canada. Clamp ground cable to the plate.

[Crossy]

Don't know if allowed in LOS, but I was allowed to use a 12 inch by 12 inch bay 1/4 inch steel plate, buried one meter, instead of a groud rod in Canada. Clamp ground cable to the plate.

I wonder how long an unprotected steel plate will last.

I'm tempted to bash in a few 15mm re-bar rods welded together at the top (can you get galvanised re-bar in Thailand?

[MiKT]

Crossy

As noted in Annex A of EN 50162-2004, at the point where stray dc –current leaves the metal structure an anodic corrosion takes place at the metal/electrolyte interface resulting in oxidation (dissolution) of the metal. This dissolution follows the Faraday electrolytic law, which for a bare steel surface means that an anodic current equal to 1A dissolves 9.1 kg of steel per year.

Unless your generator is shoving out imense amounts of DC Stray Current (don't let any tall people or large 4 legged animals walk in your garden when the gen is running as the step potential would be very dangerous - which is very, very unlikely) so it's almost certain they did not put in a 2.5M earth rod for you, the amount of oxidization would be far too much for a normal rod, no matter how acidic the soil.

Looking closely at the pics, the shape of the rod does not follow the normal corrosion pattern for a long rod, why would it corrode like that unless it was close to a lot of buried steel. .Also the pointed end indicates that it was sharpend to make it easier to put into the ground. Please dig down and see what you can find and let us know.

Crossy, following on from this, it really is inconceivable that your earth rod corroded away in such a short time without a huge amounts of DC stray current attacking it.

Check out these two sites for simple details of copper clad earth rod and how resistant it is to corrosion.

http://www.paigewire.com/pdf/minimize_corrosion.pdf

http://www.aflglobal.com/productlist/Product-Lines/Conductor-Accessories/Copperweld-Wire-and-Strand/doc/Corrosion-on-Buried-CCS---FCW-2011.aspx

NB A direct lightning strike could damage an exposed cable (as shown in the Saudi incident) but because of the lightning strikes VHF it very quickly dissipates into the earth and after about 18m depth there is not much effect (it is normally only the top portion of an earth rod that has any real earthing effect - in reasonably damp soil). Therefore the strike would not have damaged the bottom portion of your rod (if you’ll pardon the expression) whilst leaving the top half (and your cable) undamaged.