no earth

[Stroppy]

Two rods screwed together, so 8 feet.

 

[Geordie Spark]

how deep have you gone?

All the way to my bow locks.

 

[Engineer54]

Two rods screwed together, so 8 feet.

They weren't 3/8'' rods then, if you were able to couple them together!! The 3/8'' things, are the twigs that you can't couple!! lol!!

Go back and test that new rod installation in 6 months time, you'll see almost certainly see an improvement on the present 44 ohms, ..and it will continue to improve for the next 18 months or so, as the soil slowly compacts tightly around the rods....

 

[ackbarthestar]

Exactly, I told you that 'twig's were the way to go.

Wack a 1.2m 'twig' in and the the Ra will decrease because of the contact resistance around the electrode.

Better still, back fill with conducting cement and you've increased the contact resistance immediately.

As an aside, it only works when the soil conditions are right and Hong Kong, Gibraltar and most of Norway plus the Himalayas and a couple of places just outside our local pub are not the best places for any 'twig'

 

[Engineer54]

Exactly, I told you that 'twig's were the way to go.

Wack a 1.2m 'twig' in and the the Ra will decrease because of the contact resistance around the electrode.

Better still, back fill with conducting cement and you've increased the contact resistance immediately.

As an aside, it only works when the soil conditions are right and Hong Kong, Gibraltar and most of Norway plus the Himalayas and a couple of places just outside our local pub are not the best places for any 'twig'

You can sum that up very easily, where twigs are concerned No-where will twigs be any good!!

I wouldn't say Hong Kong is a particularly bad area for creating a TT system, far from it in fact, depends where your trying to create the system. Remember Hong Kong isn't just the Island(s), it also incorporates a section of the mainland too!! lol!!

The earthing on both the Stations and the tunnel overhead rail system, as a whole, was impeccable on the MTR (Mass Transit Railway). I know because i was responsible for large sections of it, along with various much needed CP systems to suit!! ..lol!!

 

[Stroppy]

Oops my mistake, they are 5/8" not 3/8". These mediaeval measurements confuse me! 10 or 15mm make more sense to me. (see: What we SHOULD have been taught in our senior year of high school - The Oatmeal )

I will try to remember to retest in a few months time, as hopefully the soil around the top rod will have settled a bit. At the moment with all the movement from driving it in it is flapping like a dick in a shirtsleeve.

As an aside, it only works when the soil conditions are right and ...a couple of places just outside our local pub are not the best places for any 'twig'

Oh I don't know, all the wee would keep the soil nice and moist! Although may corrode the rod quite quickly.

 

[ackbarthestar]

I will concede that you are referring to a fully integrated system over several miles - hardly 'twig' territory.

The basic two up two down domestic installation with a 'twig' would suffice, IMO, as long as you get a reasonable Ra of less than about 50 Ohms and as you say this value is likely to decrease as the electrode beds in.

In any case, unless you can get the value of Ra below 1 Ohm you'll need supplementary protection Earth fault protection from RCDs

 

[ackbarthestar]

Oops my mistake, they are 5/8" not 3/8". These mediaeval measurements confuse me! 10 or 15mm make more sense to me. (see: What we SHOULD have been taught in our senior year of high school - The Oatmeal )

I will try to remember to retest in a few months time, as hopefully the soil around the top rod will have settled a bit. At the moment with all the movement from driving it in it is flapping like a dick in a shirtsleeve.


Oh I don't know, all the wee would keep the soil nice and moist! Although may corrode the rod quite quickly.

Backfilled with rubble with an overlay of concrete and tarmac ? You'd probably need a 10m RSJ pile driven into the ground

 

[Engineer54]

I will concede that you are referring to a fully integrated system over several miles - hardly 'twig' territory.

The basic two up two down domestic installation with a 'twig' would suffice, IMO, as long as you get a reasonable Ra of less than about 50 Ohms and as you say this value is likely to decrease as the electrode beds in.

In any case, unless you can get the value of Ra below 1 Ohm you'll need supplementary protection Earth fault protection from RCDs

Well for a start i wasn't referring to twigs in my assessment of Hong Kong, just that it isn't a particularly ALL bad area to create TT systems. I don't think i've ever seen a 2 up, 2 down residence in Hong Kong, they are all high/medium rise apartment blocks, or massive residence's of the very rich!! lol!!

Nope, ...it wouldn't, for a kick off there is no-way that a twig will offer any form of a stable TT system to an installation.

Twig electrodes are no good to man or beast, they are little more than the size and thickness of test spikes used for testing Real electrode rods... lol!! I've actually never seen one either, and certainly not in any of the countries i've worked in. Say's a lot for the UK, when you think about it!! lol

 

[Engineer54]

Oops my mistake, they are 5/8" not 3/8".

I will try to remember to retest in a few months time, as hopefully the soil around the top rod will have settled a bit. At the moment with all the movement from driving it in it is flapping like a dick in a shirtsleeve.

That's why most electricians that do a lot of TT installations use a SDS with either a shop made or home made driving head, to drive rods into the ground, ....and in a fraction of the time it probably took you. ...lol! It also considerably reduces the flapping about of the rod during installation, that you get when using a club hammer or the like!!