I did see TWO NERs in the 33 - 11 kV sub at the university...
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E
Engineer54
We perhaps older guy's know there are several methods of creating a decent TT system!! The problem is, the younger sparks, ...that just seem to be playing at creating TT systems, because they know no different.
....What are you and other lecturers teaching these new students of today at collage, about providing a functional TT system?? As far as i can see, there being taught to totally rely on a RCD device for there earth fault protection, and only need one of these pointless 1-2m 3/8'' rods, that can't be extended even if you wanted
too.
The problem with your suggestion, is that you would need to drill a 50 to 75mm bore, that you can fill with the conductive cement, or bentonite mortar. Not particually cost effective on a domestic installation, as it would involve the hire off the drill and rig. Personally, i would consider 3m as the minimum depth, but 2 X 1.2m rods is i suppose better than One rod!!
....What are you and other lecturers teaching these new students of today at collage, about providing a functional TT system?? As far as i can see, there being taught to totally rely on a RCD device for there earth fault protection, and only need one of these pointless 1-2m 3/8'' rods, that can't be extended even if you wanted
too.
The problem with your suggestion, is that you would need to drill a 50 to 75mm bore, that you can fill with the conductive cement, or bentonite mortar. Not particually cost effective on a domestic installation, as it would involve the hire off the drill and rig. Personally, i would consider 3m as the minimum depth, but 2 X 1.2m rods is i suppose better than One rod!!
I think the opinion is that at depths beyond 1.5m are not prone to seasonal variation, Certainly in this country.
Bentonite is a gel/slurry, create a pool and drive in your rod, it will pull the bentonite down, it will help a little but not much. Time is the best, the soil will consolidate over time reducing the Ra the most.
Marconite is an aggregate added to cement to create a conductive cement, costly as E54 has mention, cheaper to add several rods. Though in hard ground it does have its place.
I'd just couple 2 5/8 rods 1.2 or 1.5 long. This will put a minimum of 1 m out of the reach of seasonal variation. But as a minimum add at least one other, i tend to try and connect an electrode at every DB, along with extraneous conductive parts this soon reduces the Ra.
Just to add, a rule of thumb for parallel rod resistance percentage improvement.
Second rod 60%
Third rod 45%
Fourth rod 35%
Regards Chris
Bentonite is a gel/slurry, create a pool and drive in your rod, it will pull the bentonite down, it will help a little but not much. Time is the best, the soil will consolidate over time reducing the Ra the most.
Marconite is an aggregate added to cement to create a conductive cement, costly as E54 has mention, cheaper to add several rods. Though in hard ground it does have its place.
I'd just couple 2 5/8 rods 1.2 or 1.5 long. This will put a minimum of 1 m out of the reach of seasonal variation. But as a minimum add at least one other, i tend to try and connect an electrode at every DB, along with extraneous conductive parts this soon reduces the Ra.
Just to add, a rule of thumb for parallel rod resistance percentage improvement.
Second rod 60%
Third rod 45%
Fourth rod 35%
Regards Chris
E
Engineer54
Your description of Bentonite is completely wrong Chris, Firstly you do not just create a pool and have the earth rod take the slurry with it.... that would be a complete waste of time and of the bentonite. Who on earth taught you that method??
Secondly Bentonite is a recognised throughout the industry as a working enhancement of earthing electrodes and as such a proven system. Your description of '' it will help a little but not much'' is totally incorrect. Maybe in the installation method that you propose, but certainly not, when used correctly!! ie, ...in a bore or in a excavated trench etc!!
Used correctly Bentonite will fulfill it's function of substanually reducing the resistivity of the surrounding soil for probably the life of the installation, as it will continually absorb water/moisture and hold that moisture, it's also in it's own right, a conductive medium.
As for the other points you brought up in your post, ...Well there certainly better than most of the TT systems that you'll find in the UK, ...that's for sure!! lol!!
Depth equals stability first and reduction of Ra values secondly. Both are important factors in creating a ''Functional'' TT system....
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Your description of Bentonite is completely wrong Chris, Firstly you do not just create a pool and have the earth rod take the slurry with it.... that would be a complete waste of time and of the bentonite. Who on earth taught you that method??
Well, it's a method i've used, suggested by several chartered engineers who work for two of the largest Earthing solutions company's in the UK. where drilling and back filling with Bentonite would be to costly/time consuming. As i said create a pool and drive in the rod keep pouring the mixture and this will be drawn down with the rod, this will fill most voids around the rod and lower its resistance. Jobs a good un
Secondly Bentonite is a recognised throughout the industry as a working enhancement of earthing electrodes and as such a proven system. Your description of '' it will help a little but not much'' is totally incorrect. Maybe in the installation method that you propose, but certainly not, when used correctly!! ie, ...in a bore or in a excavated trench etc!!
Used correctly Bentonite will fulfill it's function of substanually reducing the resistivity of the surrounding soil for probably the life of the installation, as it will continually absorb water/moisture and hold that moisture, it's also in it's own right, a conductive medium.
Not disagreeing if used as a back fill, though there is a limit om the radius and its effectiveness. Though certainly in many domestic situations i don't see many drilling holes LOL. The method i mention is relatively effective without to much hassle. Though i would probably use Marconite if i was trenching, it doesn't rely on water, Bentonite can dry out.
As for the other points you brought up in your post, ...Well there certainly better than most of the TT systems that you'll find in the UK, ...that's for sure!! lol!!
Depth equals stability first and reduction of Ra values secondly. Both are important factors in creating a ''Functional'' TT system....
Regards Chris
E
Engineer54
Tell me the name of this earthing solutions company, ....i'd love to talk to these C'eng's on this utterly useless application method of bentonite...lol!! The slurry would have to be so thin and therefore weak in bentonite content to even be drawn down with the rod!! For bentonite to be an effective enhancer, there needs to be a volume of the mixture surrounding the rod for it's full length in the soil. Having bits here and bits there, that would be so thin, it'll useless and probably dry out in next to no time!!
Check with any of the manufacturers of bentonite powder or granules and see what they say is the standard installation method!! You'll find that it is exactly the same as the Maronite method. Powdered bentonite being favoured for bores and granules for excavated trenches...
Check with any of the manufacturers of bentonite powder or granules and see what they say is the standard installation method!! You'll find that it is exactly the same as the Maronite method. Powdered bentonite being favoured for bores and granules for excavated trenches...
Well i think you need to consider when your driving several rods at depth the void left by the coupler will allow sufficient amounts of Bentonite to be drawn in. Once the gel begins to swell this will create a good contact with the rod where a void made by the coupler would of existed.
As for the Ceng, im not going to disagree with their techniques, im happy with it, it works to a degree. I can assure you they know there stuff Lol.
Regards Chris
E
Engineer54
I considered it for about 5 seconds flat Chris, commonsense and experience tells me there is not going to be any significant volume of bentonite surrounding a driven rod(s) of any depth. The Fact is, ....the minimum bore hole required for a bentonite enhanced earth rod is 50mm, the standard bore hole is 100mm, ...So you tell me how a thin slither of bentonite around a rod is going to do anything to enhance it's surface area and lower it's resistivity volume?? ...It can't, can it!!!!
If these Engineers advocate this method of installation for a bentonite slurry/mortar, then i would have good reason to doubt the term given to them in that ''They Know There Stuff' because clearly they Don't!!! ...It won't and can't work!!
If these Engineers advocate this method of installation for a bentonite slurry/mortar, then i would have good reason to doubt the term given to them in that ''They Know There Stuff' because clearly they Don't!!! ...It won't and can't work!!
E
Engineer54
The problem with that analogy is that you were not talking about 10metres in your original post you were talking 2 metres!! But even so, even driving 10 metres you are not going to end up with a bore of 50mm or more!! Not that anyone would consider driving 9 or 10 rods into the ground. Perhaps this is why you were not impressed with the results of bentonite, and why what went into the ground didn't last very long??
Bentonite is a highly absorbing medium and will continually absorb moisture from rainfall etc. It holds it's moisture for considerable periods of time, so is even good for areas of low seasonal areas of rainfall.... But only IF and WHEN it has been used correctly. I'm not saying it's the best, it's not. .....Conductive cement or Marconite would fill that title, but it is the a good runner-up in this field!!!
DEEP EARTH GROUNDING VERSUS SHAL
http://www.copperinfo.co.uk/earthing/downloads/pub-119-earthing-practice.pdf Page 95 - 96
These are a few ive managed to dig out, im sure there is others, so im not the only one LOL.
Regards Chris
http://www.copperinfo.co.uk/earthing/downloads/pub-119-earthing-practice.pdf Page 95 - 96
These are a few ive managed to dig out, im sure there is others, so im not the only one LOL.
Regards Chris
Well, im not saying the method doesn't work, it does to a degree, you drive in 3 5,8 rods and you will be surprised how much gets drawn down and there's no doubt it improves the Ra. Its a case of is it necessary i suppose, the soil will consolidate over time.
E
Engineer54
Not sure what your trying to prove with this link?? If it's driving 10 metres (several rods coupled) or more of earth rod in the ground, then as this link quite rightly points out, the good likelihood of those rods snapping or bending after hitting hard obstacles... (they won't be referring to 1.2m rods either, but 3m rods) Normally and as a matter of course, you would bore rather than drive (dependant of ground conditions) past 6 to 8 metres....
Chris, i've been involved with the creation of deep ground fields and other conventional and un- conventional grounding systems of deep and shallow earthing systems for a multitude of different purposes for over 30 years now. And in just about every type of soil condition i can think of, in different climates. I know what does work, and i also know what doesn't work, because i've had a few of them too in the early years. All i'm saying to you is, that relying on a bentonite slurry to be drawn in, as your driving a rod into the ground Won't and Can't work, for the reasons i've given you!! And probably why you were not too impressed with the results yourself...
E
Engineer54
An earthing system made up of earth electrodes is installed with a minimal expected lifespan of 30 years or more. So if as your saying in your original post, intimating your method wasn't giving lasting results, then clearly it ''Doesn't work'' does it??
A
alarm man
you can get a decent tt system with 2 rods driven into the ground,its what we do its in the regs we dont need trenches we dont need to drill for oil just to put a rod in,i think were over complicating matters here..
E
Engineer54
I don't think were talking about the easily achievable low standard of what's required in the Reg's here. But rather in the type and/or method of installing an enhanced earth rod Alarm Man.... But i'm pleased to hear that you couple your rods to get that bit of extra depth on installations. ..lol!!
E
Engineer54
You dreampt it i think, but they do want a decent TT system at domestic installations.
But It can be by plate(s)/ rods(s) or tape, etc...
A
alarm man
it worked e54,78 ohms,well within regs..lol,maybe you could discuss it on the iet forums,lol
I have their "regs" but the French is beyond me! Onto another TT myth then - is in true that in the "olden days" they would test how good an earth you had by connecting one side of a light bulb to live and the other side to the rod - the brighter the light the better the earth. I so want to try this!
E
Engineer54
Be my guest then ...lol!!
T
trev
You would be willing to hold a LAMP against an earthed rod then touch it with a live cable?
Do you promise to get your mates to post the video on youtube, there's a good chance you may be unable to
Well..
In Canada I saw out in the country single wire HV with earth return....
In Canada I saw out in the country single wire HV with earth return....
You would be willing to hold a LAMP against an earthed rod then touch it with a live cable?
Do you promise to get your mates to post the video on youtube, there's a good chance you may be unable to
It's on my bucket list!
Well, I believe there's a name for this - Live Working!
Try industrial insulated tongs, marigolds, wellies and a 11kV mat !
Well i wasn't trying to prove anything as such, you said the use of Bentonite in the way i described was completely wrong. The method is used and it works to a degree, better than peeing on it LOL. The point i was making i suppose was that unless you are going to extreme measures soil consolidation will have the biggest effect on the Ra.
Even if you use Bentonite or marconite there's not going to be a massive reduction, roughly a 10 % reduction.
Take a soil resistivity uniform 120 ohms, 3 x 3 meter rod's, 1 rod 15mm diameter and another rod 50mm and 100mm using Bentonite.
The 15 rod comes out at 41 ohms, the 50mm rod comes out at 33 ohms and the 100mm at 29 ohms
So if we install 2 x 3 meter rods, 1 at 15mm and the other 100mm we have:
15mm = 24.6 ohms
100mm = 17.1 ohms
So as i said, if your driving in a few electrodes your not going to gain much by drilling 2 100mm holes and back filling, taking into account cost and time. Just add a little Bentonite as you drive this will help to over come soil consolidation and far less hassle. Your not going to gain much, but then you don't gain that much at 100mm lol.
Regards Chris
K
Knobhead
T
trev
No dispute about whether it would work or not Tony, I just have visions of him in someone's garden with a pendant in one hand, a cable in the other and doing a little dance acting out a scene from The Green Mile
A
alarm man
K
Knobhead
Where did you get that picture of me from? That was at school playing with a Van der Graaff generator or was it the Whimshurst machine.
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E
Engineer54
Let's face it, there are cut off points for everything in our industry, you plan/design systems etc, to the requirement of the installation. Same with roded earthing systems, your not going to install a 6m string of magnesium brick anodes to TT a domestic, but you would if you were protecting a very expensive and vital pipe line...
What i will say is, that TT systems today in the UK seems to have become a lost art, along with MICC and other proven wiring methods that now seem to be classed as ''Specialist Only'' lol!!
We could go on and on talking about the various methods, along with there advantages and disadvantages, as TT systems cover a vast area of uses and requirements, depending on it's situation. And that's before considering passive and active Cathodic Protection systems...lol!! So on this one, i think it's better to agree to disagree!! lol!!
Well im not disagreeing with many of your points, and i am coming from a domestic small commercial direction where cost dictates to a degree.
Certainly on unfavorable soils, consolidation can take time i agree, though as i mentioned earlier on there is a place for soil enhancement without doubt, poor soils will require help.
The 10% comes from the manufacturers, though they do expect greater results, certainly where its used with a poor soil you would expect a far greater result than 10% than if you didn't.
Well when you talk about top soil to what depth? If you carry out a ground resistivity test, you can test the layers to a good depth, certainly below the top soil lol. Using the 4 pole tester and a Werner graph you can assess the ground resistivty at different levels, then you can calculate as you mention the different electrodes in that given soil. This gives you an approximation of the expected Ra.
Well 100mm will lower the Ra though it soon level's out after that. And certainly in poor soils there will be an improvement greater than the 10% and also enables an electrode to be less prone to seasonal variation.
Making a slurry, works to a degree, and you don't use too much, so cost is not an issue really, so its a good option for installations where cost is an issue. Voids will be created by the coupler and it will fill that void. Im not disagree 100mm bores are not a better option, cost does then come into play.
So i agree there's cut off levels and we have to install a Earthing system which is with in the balance of the client yet fit for the purpose.
Well i think it would be a good thread " Cathodic Protection", Galvanic and electrolytic cell corrosion, and the use of sacrificial anodes and impressed currents lol.
Regards Chris
K
Knobhead
Off you go then. But somehow I don't think there will be to many take up on it. Would be interesting though.
Just bumping some threads in the Electrical Wiring Theories and Regulations forum category here on our Electricians Forums. If this specific topic isn't current, just ignore it, it'll drop off the list in no time. However, if it's something you'd like to contribute to, feel free to reply and bring it back into current discussion.
Sorrrrryyyy lolHmm
Thanks Dan (not), I just read through 4 pages of this topic only to realise it was from 5 years ago.
I'm not amused.
Check the date on the others then because some are from 9 years ago! lol
Just bumping some old longish threads that had quite a bit of traffic back when they were posts. Some are sometimes still applicable so helps keep the waffling going.
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