Getting a good earth return using copper rods.

What is your definition of "proper earth return"? You do not use an ohm meter to measure the resistance of this installation. What kind of operation do you have?

It is a house with a single phase 240 vac 50Hz 2-wire overhead supply. The return path for the protective earth is via an existing copper rod driven into the ground.

A 'proper' earth return is one with a resistance low enough to allow the anticipated fault current to trip the MCB's and RCD's in the appropriate time, and to avoid 'high' contact voltage. At present the rod shows a resistance of 200Ω - which is too high.

There is also an underground lead water pipe, but we are not allowed to use that as the prime earth return, except that it has to be bonded to the copper rod along with all the other exposed metal pipes and equipment.

The ohmmeter connected between the copper rod and lead pipe reads 400Ω

The overall resistance drops to 10Ω in the final loop test.

Grounds should not show more that 1 ohm generally, less is better. This allows the fault path to generate the greatest fault current and allowing safety devices to operate at their best!!!

You need some expert advice and quickly.....its simply not safe!!!

Yes, I do need advice. That is why I asked the question.

Your next option would be a ground loop. A loop of bare cooper wire usually 3/0 around you building and buried at least 36" in the earth. Cadwelded leads should come off of the loop and bonded to all local steel, and electrical equipment. If that doesn't work you can the go to a signal reference grid contact ERICO for details.

US code would say two 6' 1/2" dia copper rods 6' apart in the soil. I can't imagine you have dry soil in the UK but what type of soil and is it fill?

I always make sure that the rods are not under an overhang as the soil in there tends to dry out. Make sure the rod is a good 2' from the foundation.

Anyway the ground loop suggested should take care of everything.

Thanks. ca1ic0cat: Your suggestion about the rod(s) being 2ft from the foundation makes sense, and points to the possible cause of the problem I have, because the existing rod is inside the house.

I will try it out over the weekend.

Inside the house? This is the first time I've heard of that. Interesting.

Definitely put the rods out in soil that is exposed to the rain. You need the moisture to provide a good ground path. The wetter the better.

Thanks, but digging a 3ft trench around the building is out of the question.

Dear horace40,

After conducting a utility underground survey insuring that the underground is clear, knock in another ground rod. If the first ground rod was an 8 footer, install an additional ground rod at a distance of at least 9 feet from the first ground rod. Bond the loop and measure again. The improvement may be up to 30% better (lower). If the resistance is not acceptable, add another ground rod! Good Luck and make your connections good.

Thanks Guest.

I will try my luck with 4ft rods.

I would be curious how the resistance improved after each additional ground rod.

Even 4 footers should show improvement...Let me know, Thanks

To MasterEmaybe

I knocked in a 4ft rod into wet clay-like soil. The resistance was 230Ω. Still too high.

It was hard work and the thought of going deeper to 8ft seems like an impossible job.

How are 8ft rods knocked in. Knocking in 4ft at a time does not work because the top end is damaged making it impossible to join the next rod to it.

And making an 8ft rod means you can't reach up to the end with the hammer, and standing on a ladder means the rod buckles and flexes sideways rather than going down.

Hello horace40, Toomuchfun here.

I had an issue with an earth ground at a property that I own that has a well and barn for livestock. It also has as a back up, electric fence. This property is on a sandy ridge that is high and dry much of the year. The electric fence doesn't work very effectively in the dry season as the powder dry sand doesn't complete the shocking circuit very well. 10 ft long ground rods did not resolve the problem. So I got six ground rods and cut two in half and welded them to the others and now had ground rods that were 15 ft long. I got some hard copper pipe and used a crimping tool to bind it in place over each of the welded joints to insure that the conductivity would not be impaired. I drove a rod into the ground at each corner of my pasture fence and added additional wires in such a fashion that when the cattle touched the live wire they also would contact a ground wire. The deeper ground rods solved the problem, as the 10 ft long rods simply were not long enough to provide a good earth ground in a dry season.

ENOUGH OF THIS ABOUT THE EARTH GROUND! You simply must do something about the LEAD water pipes, "they are killing you" slowly!

TMF

Thanks Toomuchfun.

Strange isn't it! - you spent all that time and effort to create an electric shock - and I am thing the same to prevent electric shock.

Unfortunatley I haven't time to give a detailed answer but hope to return to this discussion and flesh things out.

Furse have a range of earthing materials which can help. They also market a material called Marconite which reduces soil resistivity. I'm not a fan of this material as I would be concerned about longevity.

Briefly:

1. Do not rely on utility pipework; this changes over time (for example - get rid of your lead water pipes!)

2. Spikes are best but have obvious hazards. Be aware and avoid underground services.

3. Avoid soft ground. The spike should be difficult to drive in. Soft ground dries out in summer and you will lose your ground connection.

For a technical discussion on the machinations of IT earthing see Schneider Cahiers techniques no. ECT178

Responding to 14

Marconite is a compound for creating conducting concrete, and is not generally used for mixing with soil, the results could be indeterminate there.

Used as designed, Marconite has very good longevity, samples have been in long term testing for many, many years and this will continue.

My connection with Marconite was as Technical Manager for the team that created it. I thus have an interest. However, I left that Company some 20 years ago but did not wish the apparent slur to pass by without comment.

I am sure that Furse will be able to provide chapter and verse if required.

Sleepy

Mea culpa, just what happens when you are in a hurry. Marconite is the material for adding to concrete, Bentonite is the material for adding to soil. The latter is used occasionally here in NZ however I see no barrier to the material migrating through time. Marconite concrete would presumably have the same longevity as normal concrete.

The intonation of the word slur is that there was some intentional purpose in disparaging this material. This is not the case.

Sleepy, I am interested in knowing more about the genesis of Marconite, you know the who where what why etc. I tried to contact Furse but they are not the manufacturer, where is the best place to start. DW

I presume your grounding connections are clean and tight.

No earth return? No neutral to your meter panel?

Typically, the only time the neutral and grounding wire are bonded together is in the meter panel. The ground rod is connected to this neutral terminal and from there a neutral and ground wire go to their separate bars in your circuit breaker panel.

At least that's the way it used to be per the NEC.

I believe in Europe the ground and neutral are ONLY bonded at the substation where the 220 volts is generated.

What happens here is different as they do not have an earth from the substation (if I understood the original poster correctly), so I would guess that they need to "make" an earth and bond it to the neutral in the mains box AND drive a long rod into the ground and bond this to the earth busbar in the box......we had a similar system here in Germany many years ago.....the problem is that some electricians only wired in 2 core cables.....if you want to use ELCBs, you need to replace all the 2 core with 3 core first!!

In the house/building, the earth and neutral MUST therefore be kept seperate at all times and run as normal wiring rules dictate......then modern ELCBs will work just fine and shield people from bad electric shocks.....

On re-reading this, I find it difficult to put it into words that cannot be missunderstood in some way, if anyone needs a bit more detail, let me know and I will try and help.

Andy,

In the good ole US of A, I do not think we have a ground wire per se from the substations either. There is a static wire that runs along the top of our 4160V power poles that I think is for lightning protection. This wire is connected to a ground wire that runs down the pole and ends is a spiral on the bottom of the wooden pole which is set in the ground. The transformer at the drop to your house is probably connected to this ground wire. The neutral connection at this transformer is connected to the messenger wire that carries the two hot wires (230 hot to hot, 115 hot to neutral). This is the wre that is connected to the neutral/ground lug in the meter panel. This is conjecture based on my personal experience. Everything I know is wrong.

SEE WWW.FMSUDAFIX.COM

Thanks Guest for the sudafix link.

Hay i'm Sunil, before i could go any further, i would like to inform you about ROds only systems, how many rods r u using at present & also see the time & money consumed,

We are the sole suppliers of Marconite, if you wish to know about more advantages of using marconite plz do not hesitate to mail me on tcestorj@emirates.net.ae ..

Best Regards

Sunil

0097150-1422378

tcestorj@emirates.net.ae

ok all you need to do is purchase an RCD rated at 30 ma then the max loop impedance on the rod can be 200 ohms simples

o another idea what you have is a tt supply. it sould possable to convert to tn-c-s

that is to say you use the supply netural as the earth. but this can only be done by the supply company you must ask them to do the work. it a free service if you cna get the company to do the work ,not easy now ,was simples in the past

hope this helps [oldsparky]