Tt earthing conductor max length

[needasparks]

My last earth rod job I achieved a reading of 9.32 ohms with two 1M 5/8 rod coupled together.
The last meter was a right pig.
One thing I can't work out is why they would make a coupler that's a larger diameter than the rod, therefore
the second rod flaps around. I think the first rod should screw into the second larger diameter rod.

Dragons Den ?

 

[Engineer54]

My last earth rod job I achieved a reading of 9.32 ohms with two 1M 5/8 rod coupled together.
The last meter was a right pig.
One thing I can't work out is why they would make a coupler that's a larger diameter than the rod, therefore
the second rod flaps around. I think the first rod should screw into the second larger diameter rod.

Well done for trying!!

The coupler diameter is not that much larger than the rod. They need to be substantial as they have to do two jobs, act as driving medium in conjunction with a driving head (can't remember the correct name...lol!!) and as a solid connection between two rods. As i've stated before, it can help if you water the second rod in, but final consolidation between rod and soil will take time.
By the way, it's far better and a dammed sight easier to direct drive earth rods in the ground using an SDS drill with the rotary turned off. It reduces the flapping around (as you call it, ...lol!!) considerably...lol!!

So if you achieved an Ra of 9.32 ohms, with your two rods, expect that reading to fall even further. I wouldn't be too surprised if you checked it again this time next year you'll see a value of sub 7ohms and maybe less....

 

[Engineer54]

LOL.
I just don't like the that'll do attitude of a lot of people.
Not pointing fingers as I know people on here who join in these threads know what there talking about in general.
It's only the x5 test can throw up over 50v touch voltage if it's over 333. That's all I'm saying lol

That's exactly the point i've been making!! And creating TT systems is probably the worst culprit of them all!! Not helped at all by the Poo in BS7671....

 

[Chr!s]

What's better a stable Ra of 40 ohm's or a stable Ra of 200 ohms.

And what is your reasoning based on?

 

[IQ Electrical]

What's better a stable Ra of 40 ohm's or a stable Ra of 200 ohms.

And what is your reasoning based on?

Precisely, no difference in real terms, you either have a reliable TN value of Ra or you don't, 200 Ohms allows massive headroom for freezing/drying before the 1667 Ohm true maximum is reached.

I was starting to feel lonely in my understanding of TT systems, just because you've done something for 40 years and worked on some big jobs doesn't mean that your methods are up to date with technologies that didn't exist in the old 'use the gas/water pipe as an electrode' times.

 

[Engineer54]

What's better a stable Ra of 40 ohm's or a stable Ra of 200 ohms.

And what is your reasoning based on?

Based on the present UK way of doing things, it has to be the 40 ohm every time, as that probably will be stable, whereas the 200 ohm will in all likelyhood be via a single short thin spike, and ''Won't'' be stable. 40 ohms and the bonding of the gas & water pipes, could well give you some form of independant disconnection means, whereas you can forget all about that with a 200 ohm Ra. Not only that, if you get down to an Ra of 40 ohms, there's a dammed good chance of substanually bettering it, Not that many of you will, or even think about it. ..lol!!

Precisely, no difference in real terms, you either have a reliable TN value of Ra or you don't, 200 Ohms allows massive headroom for freezing/drying before the 1667 Ohm true maximum is reached.

I was starting to feel lonely in my understanding of TT systems, just because you've done something for 40 years and worked on some big jobs doesn't mean that your methods are up to date with technologies that didn't exist in the old 'use the gas/water pipe as an electrode' times.

Sorry but like it or not, 40 Years experience of being involved with just about every form of TT systems, across the spectrum of industries, means i know what i'm doing!! So pray tell me IQ in your own vast knowledge of installing TT systems, ...what has changed so dramatically in the installation of a TT system, ....Of Any Size, or for any installation?? The only thing i can see, is this UK max 200 ohm Poo your trying to defend and the reliance on an RCD to cover your arse!! New technology, do me a favour!! lol!!

Errr, ....when did i state the using of gas and water pipes as the electrode in any of my posts?? Or are you trying to just muddy the waters a little here?? lol!!

If your somehow magical 200 ohms gives you massive headroom, just think of the headroom level, if you put a little more effort into the TT system with a substantially lower Ra value!!! But then, that 200 ohm can only work while your RCD is functioning correctly!! To be honest this headroom thing is just another load of gobbledygook, totally meaningless rubbish. You shouldn't be relying on an RCD for coverage of ground soils freezing and drying, the TT electrode should be deep enough in the first place to look after itself!! So you must be talking again about these short thin rods that go down a metre... Wonderful stuff!! lol!!