Earth electrode tester or not?

[D Skelton]

I see, you're proven to be in error and you run off. I thought you liked controversy and argument, yet when you misrepresent what someone actually posts in a way to try to "score points" you do not like being called out on it.

Nope, I'm off because I don't appreciate the incinuation that I'm a dick for expressing my opinion. I won't be dragged down to your level. Up until you came along I was rather enjoying the debate with Eng, now I can't be bothered.

I'm sorry if you feel you have been misrepresented in any way.

 

[Deleted member 9648]

Nope, I'm off because I don't appreciate the incinuation that I'm a dick for expressing my opinion. I won't be dragged down to your level. Up until you came along I was rather enjoying the debate with Eng, now I can't be bothered.

I'm sorry if you feel you have been misrepresented in any way.

Well done for staying restrained and not rising to it.....which is more than I did after being called a lazy sod.

 

[Deleted member 9648]

Given the sheer number and type of modern appliances found in your average residence I'd argue the average household installation nowadays would qualify as an installation with considerable current flow in the earth. The problem with the functional earth current is it's an unknown quantity. Yes, you can measure the standing global leakage current of an installation easy enough but when power disturbances occur that standing leakage will increase by an unknown factor and along with a high impedance TT earth could quite possibly be sufficient to create a neutral earth voltage value that would be a concern or inadequate surge suppression that would be detrimental to electronic appliances.

I'll have to accept your argument there as such things are outside of my experience. Can I ask if you have any evidence of actual situations where a high Ra has contributed to the scenario you describe?

 

[1Justin]

Having started this one, I feel like the outsider here now since no one has given me any abuse at all :90:. I have really appreciated all the posts though. Perhaps if I work at it I'll learn to be more antagonistic, and I can join in the fight.

 

[Deleted member 9648]

Having started this one, I feel like the outsider here now since no one has given me any abuse at all :90:. I have really appreciated all the posts though. Perhaps if I work at it I'll learn to be more antagonistic, and I can join in the fight.

This topic has always polarised opinion and ended in tears....no need to get antagonistic matey,but apologies if your thread has been hijacked somewhat!

 

[1Justin]

That's fine, it helps me slip in the dumb questions while keeping a low profile

 

[Engineer54]

And this is where we agree. Commercial/industrial/agricultural TTs I would be banging them in until I got TN values.

Do you mean to say, that your stance, on not worth making an effort to achieve stability and low Ra values is only based on domestic installations??

I'm sorry but that makes no sense to me, and gives the wrong impression to those that are just starting out in the industry that have little to no experience of TT systems and/or have poorly based knowledge, purely gained from the crap written in BS7671/OSG.

 

[D Skelton]

Do you mean to say, that your stance, on not worth making an effort to achieve stability and low Ra values is only based on domestic installations??

In my area yes, unless they had enormous gardens there's no way I could get a sum 1 ohm value.

 

[Outspoken]

Nope, I'm off because I don't appreciate the incinuation that I'm a dick for expressing my opinion. I won't be dragged down to your level. Up until you came along I was rather enjoying the debate with Eng, now I can't be bothered.

I'm sorry if you feel you have been misrepresented in any way.

That was not how it was intended so I publicly apologise if that is how it was taken, it was meant as banter and not a personal attack. Please accept my apologies for any offence caused.

 

[Guest55]

no-one is ever going to go to the effort of trying to get sub 10 ohm readings for a domestic TT
its just not cost effective for the deminishing improvements that it brings for the average home-owner.
engineering practice takes back seat to value for money in the domestic market , simple econonmics im afraid.

 

[Engineer54]

In my area yes, unless they had enormous gardens there's no way I could get a sum 1 ohm value.

Ah, but you could easily obtain a decent level of stability and with it, much lower Ra value too boot!! Which is and has been the whole essence of my position throughout...

 

[Outspoken]

no-one is ever going to go to the effort of trying to get sub 10 ohm readings for a domestic TT
its just not cost effective for the deminishing improvements that it brings for the average home-owner.
engineering practice takes back seat to value for money in the domestic market , simple econonmics im afraid.

I do not agree with that Biff, although it is a long time since I did a domestic install, I have completed works in buildings that are similar in size, and I have never accepted a reading above 1Ω and have always put in the effort to get it as low as is practicable.


For those who would like to read up on using rods and testing them, can I suggest this from MEGGA - Getting Down to Earth

 

[Engineer54]

no-one is ever going to go to the effort of trying to get sub 10 ohm readings for a domestic TT
its just not cost effective for the deminishing improvements that it brings for the average home-owner.
engineering practice takes back seat to value for money in the domestic market , simple econonmics im afraid.

Again, if you are going to create a TT system then the minimum you should be installing is 2 X 5/8'' rods. In most cases that will provide the stability required and a respectable Ra. I can't for the life of me see that as being excessive, or requiring any OTT effort!!

And on that note, i'm off to bed, ...it's been a long day!! lol!!

 

[Guest55]

i've done hundreds of earth rod installs ( no exaguration ) whilst working for a county council highways dept.
we had entire roadworks teams with mini diggers and pneumatic jack hammers to install these earth rod installations at the end of every principle street lighting network.
our goal , set by the client engineer , was 20 ohms , a good solid & stable figure in my opinion.
99% of the time we achieved it , but sometimes with extra rods , sometimes by abandoning one location and trying another spot.
i can count on 1 hand the number of times we got less than 8 ohms.
so anyone insisting that a 1 ohm reading is realistic target for a domestic TT is clearly talking out of their arse.
;-)

 

[MDJ]

I do not agree with that Biff, although it is a long time since I did a domestic install, I have completed works in buildings that are similar in size, and I have never accepted a reading above 1Ω and have always put in the effort to get it as low as is practicable.


For those who would like to read up on using rods and testing them, can I suggest this from MEGGA - Getting Down to Earth

1ohm? Get off lol

 

[D Skelton]

Ah, but you could easily obtain a decent level of stability and with it, much lower Ra value too boot!! Which is and has been the whole essence of my position throughout...

I always get a stable result no matter what the Ra value. 2 x 1200 x 5/8" rods is standard for me. If I get 20 ohms (HIGHLY unlikely) happy days, if I get 150-250 ohms, (more likely) happy days. The result makes no odds to me. The last and only install I left over 200 ohms I checked quarterly for a year (I'll admit, I WAS worried at one point) but there was absolutely no variation on the readings.

You have to bear in mind that most of where I live is about 18"-24" of top soil then straight into solid chalk. Absolute CRAP for any sort of decent TT system! Hence why the typical domestic I spec always includes type-s RCDs.

The more agricultural TTs round here 'tend' to be more in land, so better ground conditions and a much higher chance of achieving a TN value.

 

[Outspoken]

I always get a stable result no matter what the Ra value. 2 x 1200 x 5/8" rods is standard for me. If I get 20 ohms (HIGHLY unlikely) happy days, if I get 150-250 ohms, (more likely) happy days. The result makes no odds to me. The last and only install I left over 200 ohms I checked quarterly for a year (I'll admit, I WAS worried at one point) but there was absolutely no variation on the readings.

You have to bear in mind that most of where I live is about 18"-24" of top soil then straight into solid chalk. Absolute CRAP for any sort of decent TT system! Hence why the typical domestic I spec always includes type-s RCDs.

The more agricultural TTs round here 'tend' to be more in land, so better ground conditions and a much higher chance of achieving a TN value.

Is this because you cannot get a rod into the chalk or do you feel that it's electrical properties prevent a lower reading?

 

[D Skelton]

Getting two rods into chalk, although a sweaty task has never been the problem. The problem is that chalk when not soaked isn't really known for its fantastic conducting properties.

P.s. I appreciate the apology.

 

[Outspoken]

Getting two rods into chalk, although a sweaty task has never been the problem. The problem is that chalk when not soaked isn't really known for its fantastic conducting properties.

Actually calcium carbonate has reasonable electrical properties, of course better when full of the wet stuff, but within about 50m of the surface the chalk will have enough moisture in it naturally to assist in getting a better reading than you may think. I appreciate that there will be differences with location and that the permittivity of the chalk will always be a restricting factor compared to a peat or clay based soil, but you would be surprised how low you can get it even you might think the chalk is dry...the real problem is if you happen to hit a quartz or flint inclusion into the rock, or if your more toward the south west (I know you personally are not) then you can get basaltic inclusions into the chalk..which whilst having excellent permittivity is a real biatch to drive a rod into

P.s. I appreciate the apology.

Despite how I might seem sometimes, I do not set out to offend and will always apologise if I feel I have either offended or simply overstepped the mark

 

[GLENNSPARK]

Actually calcium carbonate has reasonable electrical properties, of course better when full of the wet stuff, but within about 50m of the surface the chalk will have enough moisture in it naturally to assist in getting a better reading than you may think. I appreciate that there will be differences with location and that the permittivity of the chalk will always be a restricting factor compared to a peat or clay based soil, but you would be surprised how low you can get it even you might think the chalk is dry...the real problem is if you happen to hit a quartz or flint inclusion into the rock, or if your more toward the south west (I know you personally are not) then you can get basaltic inclusions into the chalk..which whilst having excellent permittivity is a real biatch to drive a rod into





Despite how I might seem sometimes, I do not set out to offend and will always apologise if I feel I have either offended or simply overstepped the mark

i sometimes do though...