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Thread: Earth Spike.

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    Gold Member IMHO's Avatar
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    Earth Spike.

    What is the minimum depth you have to hit an earth spike into the ground? I live on a very rocky property and lightning is giving me hell. My IP cameras get hit every season and I am now trying to protect them with lan cable protectors. They are powered with POE. (Power over ethernet) All 8 wires is protected, but as you know, if the protector is not properly earthed, it means nothing. So my problem is to get these 1.5m copper spikes into the ground. The max I get to at the current point is +-1 meter. Is there something (like a meter) I can test with to see if it is properly earthed?

    My next question is, can one hit a few short spikes into the ground, connect them all with bare copper wire and get an better earth? Once again, how do you test? I want to try this at my next point to do, as I know I will not even get 500mm into the ground.

    Any other way of getting a good earth under these conditions? What about burying a steel grid 500 mm below the surface, say 1 x 1 meter dimension and connect your earth wire to that? Obviously it cannot be treated with anti rust, so will corrosion be a problem? Do you get copper mats like that? Will probably cost a grand, so it is too expensive, as there is no guarantees with lightning.

    This is what I use as a protector.


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    Last edited by IMHO; 27-Nov-13 at 12:46 PM.
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    Platinum Member pmbguy's Avatar
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    I am certainly no expert on lightning, but what we did by my thatched farm house was to erect a long pole 12m out of the ground 10m from the house. The lighting hit the pole and not the infrastructure. We stayed on a granite koppie and had many hits, but from the day we erected this pole we had no problems. We used an old rugby post, it worked like a charm.
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    Gold Member IMHO's Avatar
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    The problem I have is that the lightning strike is coming through the power line as well, not necessary from my property. That is why I want to protect the lan cable. All 8 wires, data as well as power.

    I also need to protect the individual equipment for insurance purposes.
    Last edited by IMHO; 27-Nov-13 at 12:59 PM.
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    Buy SANS 10199 from the SABS for how to install

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    There is no real measurement result, but work on 10 ohms on a resistance meter, that allows 3 clamps. 1 clamp on spike, second clamp 3-5 meters (steel rod/spike/screwdriver in ground) away from spike, 3rd clamp 7-10 meters away from second rod etc. (each authority has its own methods and results), this is what I did in the explosives industry, and every now and then on a house...

    If you fail, add another spike on a different section etc. The depth is spike level to ground, with the threaded piece 5cm out of ground to allow visual inspections every so often after the gardener was there. Eventually you should get the result down. If not, then you get an old radiator, fill it with salt water, and add sulphate??? (that blue powder). Bury this this 2 meters down, make up a sulphate??? solution in a bucket with water, about 10 liters, pour all over it and fill up hole. Retest...

    If you only want to stick to spikes, make up a crows foot. Line from house to first spike, then three lines 2 meters long, attached to three spikes about 30-40 degrees apart. Use 16mm bare copper cable and bury the lot as deep as you can. You get a copper spike joiner that allows you to thread 2 spikes together to make up a 10 meter spike if you wish, just make sure the threaded part sticks out, cause the gardener will cut it off eventually.
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    Diamond Member AndyD's Avatar
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    If you run an 'indirectory' google search you'll find all the regs you need like here or here for example.


    You need an earth spike to ground your protector, are you going to put in a spike at each camera point with a lightning rod to prevent direct strikes?

    I'll try answer some of your questions so long.

    A 1.5 meter earth spike hit 1 meter into rocky ground is very unlikely to give you a physically stable earth or a good low impedance earth (or 'Ra' reading as it's known). With good earths depth is the key. Depth means you get into undisturbed 'hard pan' ground which is compacted and high in moisture, plus the deeper you go the more contact area you get between the surface of the rod and the ground itself.

    As a rule it's better to go deep by extending a single rod with threaded couplings and extra rods rather than use several shallow rods in various locations. I usually use the 2.4 meter rods and often we use 4 or 5 coupled together to get a depth of around 10-12 meters. We use an electric powered jack hammer with a special SDS Max rod driving attachment and even then it can take a couple of hours work or more.

    Usually I'll knock in two rods coupled together and use an earth spike tester to take an Ra reading. Sometimes if it's mid week you might get lucky and 2 rods will give you a decent reading. If it's Friday afternoon you can almost guarantee the Ra will still be a fair few hundred ohms so another 2 rods get driven in on top of the first two and another reading is taken.....and so on. Usually if it gets to six rods we pick another site preferrably 20 meters away and repeat the process then tranch between the 2 sites to lay a connecting cable. Generally if you get a good Ra reading with a new earth spike it will get even better over time as the ground around the rod settles tighter against it. I've retested some rods we've installed at yearly intervals and often they're 10-15% lower impedance after 12 months and maybe a few percent better agan after 2 years.

    You can dig a trench and lay steelwork or copper earth matting in it but it needs to be quite deep and well compacted afterward. This system works better when it's put under a building foundation or slab during the build. If it's just in a hole or trench I'd use an earthing compound in the back fill such as bentonite or similar.

    Rust doesn't have a detrimental effect on an steel earth until it eventually causes the steel to fragment into smaller pieces, surface rust and even fairly deep rust won't make much difference to Ra readings.

    For testng an earth rod you need an earth impedance tester with the spikes and long leads or with some jiggerpokery you can use a loop impedance tester to another known good earth.

    I'd suggest you might need lightning rods and earth spikes at each camera point to prevent direct strikes. You should also install surge arrestors in your DB to prevent power surges caused by strikes in the vicinity of your property. Also you should earth your comms cable shielding. Depending on the comms protocol it may need a resistive ground or direct ground connection.

    *Edit* There's some pretty good info on the furse website about lightning and surge protection. http://www.tnb.com/aus/docs/furse.pdf
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    Quote Originally Posted by Jacques#1 View Post
    If not, then you get an old radiator, fill it with salt water, and add sulphate??? (that blue powder).
    I suspect you're referring to copper sulphate.
    The trouble with opportunity is it normally comes dressed up as work.

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    the stuff they put in our drinking water on the border to prevent "earth spikes"

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    yip, thats it!! couldnt get to the name If you have to test a 110 explosive magazines, and they keep failing due to bedrock, you make a plan
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    [QUOTE=AndyD;101599]If you run an 'indirectory' google search you'll find all the regs you need like here or here for example.

    I will never again give a person specific advice on how to prevent lightning strikes!! A lady asked me to make the house safer since her fax machine got taken out every rainy season. I explained that we will do the basics, if she is still not happy we'll have to go lightning arrestors etc, but thats expensive. So we installed surge arrestors in the DBs, we earthed the metal roof with spikes, earthed the electric fence properly and the gate motor tracks and motor, installed telkom surge arrestors, got lightning prot plugs for the equipment that keeps getting hit etc. A month later the lightning hit the house and boy was this client mad!! It took me getting all the info off the net, and an engineers report stating that I followed the correct protocall, and did more than what any reasonably electrician would have done. Later, thinking about it, there was two things we did not take into consideration, one was the alarm system that was directly linked in the panel, no wireless radios, the other was its an act of God, you can try your best but if its gonna happen, its gonna happen.
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