TT...installing 5/8" rods

[GLENNSPARK]

well...here I am again...this time its installing a TT system utilising 2X 5/8" rods...with the connector..:


here is the necessary gear as laid out (the 20mm PVC conny isn`t in the pic)


these are the type of rods you need...no 3/8" twigs here (apart from in that bush behind maybe)


site is about 1 1/2 meters away from the house...thats the first one in..now to connect the second onto the first ....and carry on...


still some way to go...


get it brayed in....Robert my assistant uses the fork with a bit of tape to keep the rod steady


thats a length of 10mm CSA G/Y being pulled through a length of conny for main earthing (the conny was dropped into the ground)

Ze was OK at just over 15 ohms...had to change the 16th edition setup in the board...it was configured as a split load 10 & 2....dropped another RCD in it and did it 5 & 5
happy days...:biggrin:

 

[Engineer54]

As you can tell I am sober tonight, hence boring!

Just found the bit I read from originally. It's a Megger publication called Getting Down To Earth from 2005.
It says that doubling the girth, ahem, diameter reduces Ra by approx 10%. So diameter not that important.

I have a PDF copy of GDTE on my laptop, looks quite interesting if that sorta thing floats ya boat. Dont know or recall how I got it. Maybe Megger website, not sure.

When your only installing a single rod position such as in most domestic situations, you need all the help you can get from the materials being used. How does that saying go, ...every little helps!! lol!!

 

[Silly Sausage]

As you can tell I am sober tonight, hence boring!

Just found the bit I read from originally. It's a Megger publication called Getting Down To Earth from 2005.
It says that doubling the girth, ahem, diameter reduces Ra by approx 10%. So diameter not that important.

I have a PDF copy of GDTE on my laptop, looks quite interesting if that sorta thing floats ya boat. Dont know or recall how I got it. Maybe Megger website, not sure.

I know the one you mean. But...
I'll call your Megger doc and raise you with this little number.
http://www.copperinfo.co.uk/earthing/downloads/pub-119-earthing-practice.pdf

 

[NDG Elecs]

When your only installing a single rod position such as in most domestic situations, you need all the help you can get from the materials being used. How does that saying go, ...every little helps!! lol!!

I hate Tescos!!

But yep, I agree. Did all MPBCs and Main earth in 16mm partly to keep various values as low as I could, but mainly because a retiring spark gave me a 100m reel for nowt!!

 

[NDG Elecs]

I know the one you mean. But...
I'll call your Megger doc and raise you with this little number.
http://www.copperinfo.co.uk/earthing/downloads/pub-119-earthing-practice.pdf

Interesting read by the looks of it. Have saved to my phone and will be a nice bit of bedtime reading.

I am finding this topic of earthing unhealthily fascinating!

 

[NDG Elecs]

EDIT: just read in GDTE that girth can make between 10-20% difference, depending on which of the three bits of 'research' listed you take heed of. Not a massive drop but better!

 

[Silly Sausage]

It amuses me the almost diametrical stances of certain parties on here!
There's no way Mohammed is going any where near the mountain on this subject!!!

 

[NDG Elecs]

It amuses me the almost diametrical stances of certain parties on here!
There's no way Mohammed is going any where near the mountain on this subject!!!

And so Mohammed shouldn't, the Ra would be terrible up there....much better to rod the foothills!!

 

[GLENNSPARK]

You could always try driving another rod position in further down the garden, but 30 ohms and a 1.9m depth is far better than the numpty 200 ohms suggested in the BGB!!

agreed....the levels quoted in the BGB are stupid....
and do not encourage trying to acheave stability

 

[Outspoken]

I am curious, and I am not knocking anyone here or their respective efforts, but a couple of questions;

1. Glennspark, did you take a reading from the ROB to a Test spike or from the rod to the earth point of the installation?
2. When installing rods does anyone actually test them correctly with a rod tester?
3. When doing the testing, does anyone actually have spare rods and joiners in case they need to go down deeper?
4. What is the minimum reading you would personally accept?

When I have ever installed rods personally, or been on a job where they were installed, I have ensured that they were tested properly as they were inserted into the ground and that more rods were added until the reading achieved was an absolute minimum of 10Ω, however I have never stopped as soon as I get this value, I will add rods until I get a stable return. Over the years I have found that about 4 rods will get you into the 1Ω range (+/-0.5Ω), and a fifth rod will easily achieve lower than 1Ω, and at these depths we are talking stable return paths.

As said, I am not having a go at the technique anyone uses, I will always attempt to get the reading as near to 1Ω as possible because I hate the idea of being reliant on the RCD, like all devices they fail and the ground state within about 2.5m of the surface is too impacted by the above surface environment, man made influences and the weather/climate.

 

[44ALLAN]

It's starting to sound like a cock measuring exercise!

I'm like one of them weight lifters then that enters in the later rounds :lol:

 

[trev]

When I met Mrs Trev we were both virgins, I told her I was hung like a baby but she said that because of both of our lack of experience it would probably be ok, when I dropped my trousers she screamed and yelled "I thought you said you were hung like a baby."
I said "That's right, 8 pound 2 ounces and 21 inches long"

 

[Engineer54]

I am curious, and I am not knocking anyone here or their respective efforts, but a couple of questions;

1. Glennspark, did you take a reading from the ROB to a Test spike or from the rod to the earth point of the installation?
2. When installing rods does anyone actually test them correctly with a rod tester?
3. When doing the testing, does anyone actually have spare rods and joiners in case they need to go down deeper?
4. What is the minimum reading you would personally accept?

When I have ever installed rods personally, or been on a job where they were installed, I have ensured that they were tested properly as they were inserted into the ground and that more rods were added until the reading achieved was an absolute minimum of 10Ω, however I have never stopped as soon as I get this value, I will add rods until I get a stable return. Over the years I have found that about 4 rods will get you into the 1Ω range (+/-0.5Ω), and a fifth rod will easily achieve lower than 1Ω, and at these depths we are talking stable return paths.

As said, I am not having a go at the technique anyone uses, I will always attempt to get the reading as near to 1Ω as possible because I hate the idea of being reliant on the RCD, like all devices they fail and the ground state within about 2.5m of the surface is too impacted by the above surface environment, man made influences and the weather/climate.

Most decent sized projects, where a ground field, or with several made individual building earthing, or similar is called for, the specification will normally call for a minimum Ra of 1 ohm or less, and in some cases 0.5 ohm, depending on the nature of the project or building use... Normally on such projects, the earth rods will be lowered into Marconite or Bentonite filled pre-drilled bores, the number of which will generally achieve these low values... (eg, costs have been taken into account at the contract tendering stage)

However when talking about say, a domestic TT installation, i can appreciate that the cost of labour and materials is a limiting factor for most self employed electricians. Which is why i basically have always stated that two driven 5/8'' rods coupled together, should be the ''Minimum'' size and depth of any TT system.

By the way, that's what you would want to see, consolidated/compacted soil around the earth electrode. On multiple driven rods only the first rod will be in direct contact with the surrounding soil, those above the first coupler will not, as the coupler has a greater diameter, and why it will take time for the full Ra value of a multi-rod installation to be achieved.
Generally speaking, any detrimental environmental conditions, will only have any great effect on the first metre of the rod. (eg, drying out /freezing conditions etc...)

EDIT... Ooops, just re-read your last paragraph, and can see i've mis-read your meaning of ''impacted'' lol!!

 

[Geordie Spark]

When I met Mrs Trev we were both virgins, I told her I was hung like a baby but she said that because of both of our lack of experience it would probably be ok, when I dropped my trousers she screamed and yelled "I thought you said you were hung like a baby."
I said "That's right, 8 pound 2 ounces and 21 inches long"

A bit under developed for a Geordie aintcha??

Dunno how you dare to admit it!!

 

[Engineer54]

I know the one you mean. But...
I'll call your Megger doc and raise you with this little number.
http://www.copperinfo.co.uk/earthing/downloads/pub-119-earthing-practice.pdf

Now that is more than a half decent publication!!

 

[GLENNSPARK]

I am curious, and I am not knocking anyone here or their respective efforts, but a couple of questions;

1. Glennspark, did you take a reading from the ROB to a Test spike or from the rod to the earth point of the installation?
2. When installing rods does anyone actually test them correctly with a rod tester?
3. When doing the testing, does anyone actually have spare rods and joiners in case they need to go down deeper?
4. What is the minimum reading you would personally accept?

When I have ever installed rods personally, or been on a job where they were installed, I have ensured that they were tested properly as they were inserted into the ground and that more rods were added until the reading achieved was an absolute minimum of 10Ω, however I have never stopped as soon as I get this value, I will add rods until I get a stable return. Over the years I have found that about 4 rods will get you into the 1Ω range (+/-0.5Ω), and a fifth rod will easily achieve lower than 1Ω, and at these depths we are talking stable return paths.

As said, I am not having a go at the technique anyone uses, I will always attempt to get the reading as near to 1Ω as possible because I hate the idea of being reliant on the RCD, like all devices they fail and the ground state within about 2.5m of the surface is too impacted by the above surface environment, man made influences and the weather/climate.

1)measurement was taken as a Ze....the rod including any main earthing conductor (in this case 10meters of 10mm G/Y)

2)all my MFTs all have 2 wire, 3 wire and specific ground resistance ability...i need to get the test leads & spikes for this

3)In this case I was left with 2 rods...had it been one of my own jobs i would have certainly got three....as i have advised before in here

4)well....certainly not 200 ohms.....nor 100 ohms for that matter...lol....definately no more than 21....and then monitor it to see how much that drops...if not enough then send another rod in...but you really should be acheaving better than 21....