Earth Electrode Testing

hello I'm JW this time we can have a look at testing once again and it's earth electrode testing this time now F electrodes are not commonly used in the UK they may be more common in some rural areas but most new installations certainly do not require one and of course if you have got one though it doesn't need to be tested and confirm that it's installed properly and its impedance is suitably low and level we'll have a look at how you can test these there's the easy method which we've actually covered in another video and of course then there's the more difficult and time-consuming method which is seldom used because it's just too difficult and time-consuming now turn electrodes which are those things that you bury in the ground such as an earth rod or in some case it can be other things as well like a grid or mesh or whatever then these things do need to be tested and there's two main ways that you can test these the first method is to simply do the external impedance test and that's simply using a two wire deal between the earth electrode and the means of actual supply to the building and this is by far the most easy and hence it's the most common method that is used however the problem with this is it does require that mains power is available because of course without it's you can't actually do this so on an installation that actually has power available then that's by far the is one and we've done a separate video on that as well so it's going to have a look at that one however in the case that power is not available which certainly would be if there was a new installation power hadn't been connected yet or whatever then the alternative method is to use an actual earth electrode tester and this does not require any mains power the battery operated and of course this can be done there and without those mains power available or not uncertainly we've just installed an earth wall or something and say the actual lectricity hasn't been connected yet then that this is pretty much the only choice that you're going to have this takes considerably longer and of course you do need the specific piece of test equipment to do it with as well now plenty of multifunction testers have this built in but certainly not all of them so if you are going to be putting out electrodes in on a fairly regular basis it's worthwhile to get one that does actually include this function say some do and some do not now terms of doing these hey we've done a video on this before so I'm going to cover that in this video but so we're gonna have a look at is the procedure you can use a specific testing piece of equipment now of course it going to have the electrode installed and here's the ground here just draw it in brown here and here's the sky with the Sun in it or something and your electrode will of course be embedded in the ground and we must draw it over here in black normally the top is recessed below the ground but will they show it above here just for ease of drawing so that's your electrode that you've installed and now you need to actually use the testing equipment to confirm that it's in actual working order it's impedance is sufficiently low and typically the testing equipment will have three connections so it's could be part of another multifunction device but three wires coming out of that first wire which actually disconnects over to the or Earth electrode now we're going to draw these in blue because you can actually see them just as well so one of them goes to the actual earth electrode in the ground now the other two wires need to go to two additional electrodes which are only temporary and Jen if you buy with these things then it comes with this as a part of the set and Center their metal spikes with the wires connected and these need to be placed in the ground a reasonable distance away from the actual electrode you installed earlier they're not particularly any sort of 12 inches or 30 centimeters in length or something although if that's not suitable then longer ones can be obtained so you need to insert the other two electrodes say here temporarily on the ground and then the other one let's hang over here and note this does require that the ground is reasonably soft and you can get in there if this is a concrete late and car park or something well of course it's game over because you can't also just poke these into solid concrete or something so again this is probably something you don't need more oral areas everywhere we have this type of installation anyway now the three wires there we'll just connect across so you're going to have a wire from here to this one and Y from here to this one now in terms of the distance these have to be apart this is fairly important and it really depends on how deep in the ground this thing over here actually is an important thing is to make sure that the area that's affected by this one does not overlap the areas affected by the other two and this does vary considerably depending on the type of soil but a good way of estimating this is to see how far in the ground this years and of course you will probably know this because you unlikely and you just put it in there yourself so let's say this was two meters in length in the ground which should be a fairly short of that Road in actual fact then the total distance here between this test one here which we're going to call one number two and one this distance here needs to be at least 10 times the depth of the initial electrode so in the case of it being two meters in the ground this distance here needs to be at least 20 meters so as you can imagine these test leads are extremely long and again when you buy these at a search they do come with extremely long a test lead in a big bag so 20 meters as an absolute minimum distance and of course if this was a deep electrode say it was 4 meters in the ground then yes that means you have to go at least 40 meters away so you could be literally halfway across a field or something so definitely not very convenient in terms of the other tests and you can see why the other test is more often used so total distance there is certainly important and initially you want to do these so that they're reasonably equally spaced so in the case of 20 meters you would have say in the region of 10 meters there and about 10 meters there or conversely longer depending on the natural circumstances and then once you've done this it's question of pressing the button on the machine and then it will tell you on the little display what sort of reading you actually have now there is I have two of these is that the device can actually determine whether or not these are connected in the ground satisfactorily by measuring the resistance between the two and it does all this automatically and if you find that it's showing cut some kind of error here it means that these two are not making sufficient contact with the ground and if that's the case you're going to have to either reposition them or put them in deeper or they get longer ones or whatever else that assuming that it does actually show correctly it will give you a reading there in ohms and that is effectively the reading that you've got however that's not the end of the procedure because that only gives you in those two particular positions what we then need to do is to remove this one and you need to move it closer to the main electrode over there and then do the test again and then take it out again and I move it further away so over the side and again do the test again so you want at least three separate readings and again you don't want these to overlap so if this was say half a meter in depth you only get any closer to this and say five meters and in terms the distance here at least sort of five or six meters either side would be fairly usual if you've got have a large distance then because you can do a bit further as well now what you should get from three readings is basically the same so if you say got 68 ohms initially only got sort of seventy one and then you got sort of seventy well that's fine because they're all pretty much substantially the same and the actual reading would get is the average of those three so you simply add those three together divided by three that will give you the result in ohms and again this is not critical because you just making sure that it's within the sensible kind of range if however you did the first test and say got 68 and then you did another test and it came up with 140 and then you move it the other way and it came out as 399 then this indicates that something gone horribly wrong and it means that the other this is extremely poorly connected or one or both of these are all so badly connected and in which case you're going to have to try these in two completely different positions and of course maybe do something about the original electrode install as well but substantially the same that's fine substantially different is no good and I'll have to do the test again and depending on the kind of soil and ground you've got it may be necessary to repeat this test a considerable number of times until you can actually get satisfactory readings from it so this is not a quick test it's not convenient because you're trailing wires tens of meters across a field in most cases and of course it might be raining and getting dark and cold and whatever else so you can see now why the other test is used and this is seldom done unless this is absolutely necessary now a final point here if you get three they're the same but they're all far too high so say for example you've got three readings that came out as four hundred and fifty four hundred and seventy seven and say four hundred and sixty-eight well yes they're all reasonably close together but the average dose is in the middle of the 400s range so that's far too high because what you want to find is something in the range of 100 or less then this means that the actual electrode itself which you put in here is not sufficient so you're going to have to do something about it to reduce this value considerably so what to do if the actual resistance of that electrode is far too high well the first option is to put in a deeper or effectively longer and that Troad now the better one - these are Jenny supplied with a threaded end so that you can screw a spike onto one end and drive into the ground length of say around a meter and then you can get a coupler which screws on the top of it and then you can attach another want me to lengths on there and then drive it in the ground and if necessary repeat again and until you've got to as many in there as you can get or as many as is needed so that's certainly one option however that's only applicable if you can actually do that if you live in a shallow soil and very hard bedrock well that's not going to be working about that's certainly an option option number two is to have more electrodes so if you have the ground here you can have one in here and then look of course you can install another one over here and then there would be linked together with a suitable sized copper wire and of course equal to a third and a fourth and as many as was necessary and just as with the tests previously you don't want these to be too close together because of course if they are then they will effectively be in the same resistance area so these do need to be spaced apart a considerable distance so in the case of say 2 meter electrode you'd be wanting to put the other one sort of 20 meters away or something to make sure that it's in a completely different area and if you can have 3 or 4 then again this could extend over a considerable distance the third option is something else and by something else we don't mean just not bothering but what we can do is course not just have say a spike in the ground you can things like have a grid in the floor so instead of that you would have literally your stay metallic grid which you can then just excavate a large area and then bury this underground very handy if it's some new buildings being put up because concrete generally has this kind of metal grid inside of it so if you can get a piece to be left accessible at one edge or they take location you can actually use that as your earth electrode there are also things like tape journey made of copper so you can dig a long trench in the ground and then you can lay in the copper tape for a distance of many meters and bury that inside and there's several combination of toxic combinations of these or rods and tape and so on so whatever is necessary and it really depends on the actual area if you live in say Cornwall and you've got solid granite you're not going to be driving earth rods into that so you're going to pretty much be condemned into using grids tapes and that kind of thing and put him at any metallic object buried in the ground would do so even if you had say some farm or some things I'm old disused water pipe that went across a field for 300 meters if that's not being used to water anymore you can certainly connect to that and make a fairly good connection so that's our electrode testing and say something that's not necessarily done all the time because many installations don't actually have one but clearly if they have got one you do need to do the tests and certainly the mains power is available then it's certainly recommended to do the Peanuts test using the mains power there because it's much quicker and easier than doing the test with the three leads and all of that and the other thing to bear in mind if you are going to test it using the mains power is to make sure there's nobody in the vicinity of the electrode when you're doing the test tip if you're going to use an older test device when you're actually basically connecting that to the test machine and there can be an exposed voltage occurring on and around the position of the electrode now most modern test equipment in fact probably all of it will limit the voltage there to either 25 or 50 volts but certainly some older equipment in the ones that clear major example doesn't and you can in fact get some fairly dangerous voltages appearing there so just bear that in mind so you're not particular element on new equipment that older test equipment it certainly is so that's it for this time and until next time thanks for watching

Channel: John Ward

Views: 399,595

Rating: 4.6708531 out of 5

Keywords: earth rod, earth electrode, earthing system, earth test, Ze test, impedance test, earth impedance, 3 wire test, earth resistance

Id: G9CjydiUkAI

Length: 14min 15sec (855 seconds)

Published: Fri Dec 30 2016