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I'm looking to install a couple of vertical grounding rods for a friend's property in the middle of nowhere (very country - The earth is mostly clay, rocks and sandstone)

From the limited research I've done I believe the grounding rods should be about 2.5 metres deep and 5 metres laterally separated.

My questions are:

  1. Have I got the depths and spacing correct?

  2. How far from the building/foundation should the rods be?

  3. If I'm to hire an auger that can exhume 2.5m depth, what diameter should the auger be? I intend to use a slurry of ground enhancement material <- still not quite sure what this stuff is but I guess it's a good conductor? How many KG's for a 2.5m deep hole of "x" diamater

  4. How can I test the efficacy of the finished job? Looking at ground resistance testers (clamp style) they run in to the hundreds of dollars. Also, do you need two grounding rods driven and connected in order to use these clamp style testers? Do you clamp it on the connecting wire or individual rods? Can the connecting wire be buried or is a that a big no-no?

  5. Is something like this a complete waste of money? https://www.ebay.com.au/itm/192390605919 It seems a lot cheaper than the AUD$500 alternatives, probably for a reason.

  6. Any hot tips for what I assume will be an incredibly laborious task? I'm guessing an auger is a better choice than a jackhammer with a macgyver attachment to drive the rods, only because I'm using the ground enhancement material, otherwise a tighter drive from a jackhammer would yield better conductivity I guess.

I know if I'm asking these questions it means I'm probably ill-equipped to be doing the job but I'm making the best of a bad/dangerous situation. I'm installing CB's, RCD's and grounding on an installation that is effectively just hardwired, online and unprotected from ground faults. I figure it's a step in the right direction that simply won't happen if I don't step in. It's a case of a friend thinking his electrical "just works" but he doesn't understand the need for further protection. I hope you guys (and gals) understand where I'm coming from. Many thanks.

  • Are you also installing a lightning rod? – Tony Stewart Sunnyskyguy EE75 May 29 '18 at 16:13
  • somewhat related: How does earthing work when earth is dry? – Nick Alexeev May 29 '18 at 16:16
  • No, I don't understand where you are coming from. Get a person who is qualified to do the install. – Andy aka May 29 '18 at 16:33
  • Andy, what I'm trying to illustrate is that a professional installation is not available in this situation and I'm trying my best to make it a bit safer short of financing licensed electrical work on a friends property. As is it's an accident waiting to happen. Sometimes something is better than nothing. – totalconfusion May 29 '18 at 17:14
  • get the ground really wet so that they pound in nicely. I dig a small trench along the side of the house where I am going to stick electrodes across. I would drive them down and some at angles and interconnect them with 4 ga wire then bury. I also try to find the foundation rebar and tie the grounding to that. I also would run a ground wire to the metal pipes if it has an electric water heater. The only stipulations I see was where the first grounding rod to the service/breaker box which if you stay within 20cm from where it enters the house it will be ok. – drtechno May 29 '18 at 17:46
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This is what the generic "National Electrical Code" calls the Grounding Electrode System. It is USA-published but widely used, and widely subject to the sincerest form of flattery. My answer conforms with this Code

1) 2.5M depth is fine. 5m separation is fine, but more is better. On the other hand, copper wires aren't free so I understand if you don't put them on opposite corners. By using two rods, you are exempt from the need to test the conductance.

2) It's not critical to be close to the building. More important is to be far enough away not to strike its foundation or nick utilities. Closer to the building is somewhat better insofar as protecting the ground wires. You don't want to be on the far side of the property since you want to equipotential bond to the dirt near your house, on the off chance there is a significant voltage gradient across your property.

3) It's not a telephone pole. You don't need to auger it. Lots of people have found inventive ways to drive them. Code doesn't care how you drive it.

  • Often, a fence post driver and some patience will suffice.

  • Here's a guy working in clayish soil who does it tool-less, he adds a small amount of water to churn the dirt in the hole into mud. Works for him.

  • Some people connect a garden hose to a pipe to drive the hole hydraulically. That's kind of nice because it's less likely to damage to any utilities you might hit. A few people say this leaves excessive voids around the rod; I don't believe it. The ground does not like having voids in it, and they'll silt up after a few rains. You could accelerate this process.

4) 5) NEC rules say you only need to test if you are on one ground rod. If you use two ground rods, you are exempt from needing to test/prove the rods. Professionally around here, most installers just install two and don't look back. Simply because testing is so laborious and expensive.

All rods need to have a ground wire going back to the panel. The wire must be continuous without splices. It must be copper. It can be direct buried. I'm not sure if you can daisy chain from one ground rod to the next, but that creates a single point of failure, so I would not.

If you're that worried about it, install three.

6) Don't overthink it or assume it's laborious. Read up (i.e. watch youtube) on how others do it. It's not a highly technical project, you are sticking a copper rod in the ground. Success is when the copper rod is in the ground. Acceptance testing is "there are two rods in the ground".


Ground rods do several things for you.

  • return natural electricity (ESD and lightning) to their source, which is earth.
  • keep your electrical conductors within 250V of earth, which is useful if there is transformer miswiring or leakage that might pull it up to thousands of volts.
  • assure that you are not likely to be bitten getting in or out of the tub
  • help RCDs by providing an easier fault path

Here's what they do not do:

  • they do not return human-generated electricity to source. Quite often in the North American 3-phase system, people will wire an outbuilding and go "Hey, don't need a neutral, just drive a ground rod" -- nuh-uh. Dirt doesn't conduct electricity well enough.
  • they do not make RCDs work. RCDs don't use ground. They observe only current on hot and neutral, and want to see that current be equal. RCDs are a great option if you don't have grounding, so if there are circuits in the building that are ungrounded, slapping an RCD on them is your best bet.
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  • Thanks million Harper, this is the kind of answer I was looking for. There's a lot of information flying around regarding what's effectively driving copper rods in to the earth. Shouldn't be that complicated! I'll drive a couple of rods and make sure they have their own wires running to the ground pickup inside. I'll space them double distance apart as they are deep. The hollow bar and water trick keeps popping up, I'll give it whirl. Thanks again. – totalconfusion May 30 '18 at 18:42
  • With the NEC the seperation of the rods 6' or ~2m is all that is required more is better but at 5m that's plenty. 3/4 galvanized pipe is also an approved electrode as long as 8' or longer in the U.S. pipe comes in 10' sticks so in some areas I just use pipe. The copper wire needs to be #6 or larger 1 piece going to the panel not 1 wire from each rod. Earth testing is very quick 30 seconds with a clamp type tester but most electricians don't shell out 1500$ for the meter and the $ for recertification every 2-3 years unless working in high tech where verified grounds are required. – Ed Beal Jun 4 '18 at 12:19
  • 80% of electric fence problems in the United States - inadequate ground systems , if you are far over 50 Ohms then you are inviting problems and sticking to 2.5m which is grossly inadequate for high and dry sandstone except after a thunderstorm not before. – Tony Stewart Sunnyskyguy EE75 Jun 4 '18 at 18:51
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Try the garden hose to conduit trick. (Kiwi method)

If you can avoid rock then you don't need to drill. USe a hydraulic water drill.

Can you avoid rock and go thru clay? otherwise rent a rock pipe hammer drill

Use about 10ft or 3m hot-zinc galvanized 3/4" pipe with garden hose socket inserted snugly ,into pipe , connect hose , turn on water and tamp down 1" at a time. for about 120 seconds or more if your arms give out or worse , you hit a big rock and try again.

Criteria

A long-standing rule says that a ground rod or pipe or plate electrode must have a resistance to earth of 25 ohms or less ought to be universal.

Informal advice

If you install a lightning rod ( good idea to put a sharp short ( like Router antenna length) tungsten wire attached to insulated lightning rod wire (AWG 16x 3 strands) at least 0.3m above anything else like above TV antenna and earth bond antenna with a separate wire to ground rod so they don't share current from lightning strike and strung at 90 deg to lightning ground wire to ground rod with lighter gauge wire. Use plumbers seal on any exposed well-tightened "gas-tight" joints to prevent oxidation.

They use tungsten for high temp and sharp tips to create stronger attraction ( E field gradient) and also reduce current from tip area which stretches out duration to a lower voltage.

Refer to local standards for acceptance criteria.

Informal Test method

  • Compare voltage then resistance with Diode test or DMM between supply Earthbond, and earth supplied metal pipes.
  • better method, put a 3~4V Lithium cell between so-called Earth grounds and measure DC current with DMM 1 Ohm is 3~4Amps, 25 Ohms is 140mA avg.
  • make a block diagram , record test and results for personal records.

The rod only needs to go into wet clay/soil that doesn't dry up. WHen there is none , long concrete pad or pile is needed around rod. ( with local stipulations)

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  • I was planning on driving 2x 2.5m copper plated grounding rods in to the earth. I guess the hot-zinc gal 3/4" pipe would be a replacement for the copper rod? or Just a better way of excavating? No, I wasn't intending on installing a lightning rod, to be honest I didn't even know such a thing existed. Any comments about the AUD$300 clamp tester I listed? Would it do the job rough enough? – totalconfusion May 29 '18 at 17:08
  • For that matter just put a T fitting on the top of the pipe, plumb the water supply into the side, and bang on the top or extend the pipe and use a fence post driver. Best of both worlds. – Harper - Reinstate Monica May 29 '18 at 21:10
  • the meter is overkill for 1 job. A LiPo cell or 12V car battery and headlamp (optional) with $10 current meter in series – Tony Stewart Sunnyskyguy EE75 May 30 '18 at 1:30
  • I would not waste my time testing just drop 2 rods. In hundreds of homes in a dry area I wired none of them were below 50 ohms unless attached to a ufer ground. I don't use water just a pipe and T post driver unless a large rock is encountered it works fine (water won't help with large rocks). Note I use both multi point and clamp earth resistance meters if required for commercial work but code only requires 2 rods 8' long with 6' seperation, no testing for residential. – Ed Beal Jun 4 '18 at 12:30
  • @EdBeal Did your tests meet local requirements? Farm or urban? 80% of electric fence problems in the United States - inadequate ground systems – Tony Stewart Sunnyskyguy EE75 Jun 4 '18 at 18:43
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The conductivity to Big Earth is not a concern for grounding within a building.

Neutral and Earth conductors are bonded at the entrance to building or home right at the distribution power panel. It's obvious if you are in the building you cannot touch the external ground ...so it has absolutely no relevance to the use of the earth conductor in the building. So for things such as RCDs and GFCIs the external big ground earth is not a concern.

There is one twist to this, in that for many building the concrete rebar is normally connected to the external earth electrode to provide a better big earth scope.

Where the external big earth comes into play is for Earth/Neutral voltages, lightning and RF interference. For example if you take a long extension cable into your garden there could be a voltage difference between Neutral/Earth (remember they are bonded at the power panel) and the big earth that could kill you. The external earth stake(s) minimizes this potential hazard.

Do your Neutral/Earth bond at your power panel and use a stake to provide an external earth connection. The stake (or multiples) should be 8ft deep for NEC guidelines, and if you have multiple stakes then the ground type will influence the distance between them. Read your local standards ...but NEC quotes a 5 Ohm point to point resistance maximum.

You should read the following helpful article or this tutorial.

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    Thanks Jack. I should have made it clearer in the initial post but this is effectively what I'm trying to do. It is a county shack powered by 1000W of solar panel and a battery bank. It has no current earthing rods or even a distribution board/consumer unit for that matter. I'm trying to introduce some sanity to the electrical setup by way of installing a switchboard with an RCB, RCD's and proper grounding, the ground spikes are what I'm really enquiring about in this forum on account of I've never had to install them before. Thanks for the links they have been very helpful regarding spacing – totalconfusion May 29 '18 at 18:16
  • There is no residential required resistance measurement if 2 rods are used! It is total B.S. that the phantom voltage on an extension cord ground neutral voltage could kill. Yes I down voted! – Ed Beal Jun 4 '18 at 12:35
  • @EdBeal Just goes to show what experience you lack. This very voltage (Earth/Neutral) has been known to kill patients in hospitals. The problem is larger than that though, see here: en.wikipedia.org/wiki/Stray_voltage So before you call BS, do some research. You might read this: insula.com.au/physics/1250/L5.html I actually have experience designing hospital rated devices and it's used on separate circuits with separate earthing, they also ban the use of extension cables. P.S> have you actually read the NEC? – Jack Creasey Jun 4 '18 at 14:28
  • +1 for Jack's wisdom – Tony Stewart Sunnyskyguy EE75 Jun 4 '18 at 18:48
  • @jack Creasy. & Tony the wonder engineer with electric fences. I also worked at Corvallis good Samaritan hospital for 2.5 years as a plant electrician /engineering department, again as a extension cord phantom voltage in a hospital you have no idea what you are talking about Operating rooms a ground fault could cause a problem but in the 3 hospitals that good Sam owned all had equipment that monitored fault levels or required to be isolated! Again read the statement a extension cord long enough to kill would not be used in an Operating Room unless you designed it I guess. – Ed Beal Jun 5 '18 at 4:38

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