Earth rod query

[IQ Electrical]

You mean to tell me, that all these periodicals, reports and statics, and god knows what else etc, that surround you, hasn't been able to tell you how?? I'm shocked!! :shocked3:

As for that statement ''you're right, there's no difference. (200 and 1000 ohms)'' doesn't even warrant an answer. But why bother with installing a TT system at all , kinda springs to mind!!!

If were talking just domestic, then in all likelihood a couple of 5/8'' coupled rods, should be the minimum requirement. (Even that seems to be a problem for you, going by a previous post on this thread). But if were talking commercial premises or industrial of any size, why would you ''Not'' aim for a sub 1ohm Ra value?? ....Oh yes i forgot, your thinking about that cure all RCD that never fails...

It's often the case with obsessions that logic goes out of the window!
In terms of overcurrent protective device operation, there is no difference between 200 and 1000 Ohms, that was the point being made!
Of course you aim for the lowest value of Ra but with the usual constraints of time, money and most importantly, compliance with the regulations that we work to in the UK!

As for 'installing rods being a problem for me', it's quite the reverse, no problems here whatsoever, that's the point I'm making!

As usual, I'll continue to install my BS7430 and BS7671 compliant earth electrodes on TT installations and as usual, I'll ask again for 1 single documented case of a death or injury on a BS7671 compliant TT installation, knowing full well that there isn't any because like it or not, the system works....

 

[Engineer54]

like it or not, the system works....

Only in cloud cookcoo land!!

This all stems yet again, from ''You'' not having read of any occurrence, so clearly it's never happened!! ...I'll say no more.

So, if you manage to drive in a rod to say 2.4 Metres (good luck)

Indicates to me, that driving 2 rods in the ground is going to be a problem??...

Seems to me, there is almost a total lack of training and knowledge given towards TT systems in the UK these days. That includes both installation and maintenance. How many new electricians knows how to maintain or improve a rod installation with a poor or not so good Ra value, let alone even give it a thought?? Not many....

I don't deal in obsessions, and my logic is sound, unlike the current attitude towards TT systems in the UK. Bring back the 10 foot rods, and the 10 ohm max value ( that was almost always bettered). Either that or make all domestic TT CU/DB's all RCBO protection (even better DP RCBO's) with an upfront S type 100mA RCD. Which i think they should all be anyway. At the very least, that will give a more than decent earth fault protection to most domestic TT installations and get past (to a good degree), a failing 30mA RCD device...

​

 

[Top Cat]

Only in cloud cookcoo land!!

This all stems yet again, from ''You'' not having read of any occurrence, so clearly it's never happened!! ...I'll say no more.



Indicates to me, that driving 2 rods in the ground is going to be a problem??...

Seems to me, there is almost a total lack of training and knowledge given towards TT systems in the UK these days. That includes both installation and maintenance. How many new electricians knows how to maintain or improve a rod installation with a poor or not so good Ra value, let alone even give it a thought?? Not many....

I don't deal in obsessions, and my logic is sound, unlike the current attitude towards TT systems in the UK. Bring back the 10 foot rods, and the 10 ohm max value ( that was almost always bettered). Either that or make all domestic TT CU/DB's all RCBO protection (even better DP RCBO's) with an upfront S type 100mA RCD. Which i think they should all be anyway. At the very least, that will give a more than decent earth fault protection to most domestic TT installations and get past (to a good degree), a failing 30mA RCD device...

​

Bored, bored, bored, bored, bored, bored!

 

[Engineer54]

Bored, bored, bored, bored, bored, bored!

Of course you are!!

Just keep banging in the thin twigs and convince yourself it's a good-un!! lol!!

 

[Top Cat]

Of course you are!!

Just keep banging in the thin twigs and convince yourself it's a good-un!! lol!!

And you keep banging on like you always do without knowing what i do!

 

[Engineer54]

And you keep banging on like you always do without knowing what i do!

Or knowing what your doing!!

 

[Top Cat]

Or knowing what your doing!!

You can put clairvoyant on your CV now then!

 

[Engineer54]

You can put clairvoyant on your CV now then!

Best stick to your Meow jokes/humour...

 

[Top Cat]

Best stick to your Meow jokes/humour...

OK, i thought i was the catty one, meow!

 

[IQ Electrical]

OK, i thought i was the catty one, meow!

And you can install a purrrrrrfectly good earth rod?

 

[Deleted member 9648]

I go back to my original question... What is the point? There's no difference between 200 and 1000 ohms when it comes to an earth rods effectiveness??? This is the part I struggle to understand.

I've been ploughing a relatively lone furrow on exactly this point on here for ages....and taken a lot of flack for it.
The logic of those who scoff at the Bs recommended max of 200 ohms,and then smugly state they wont settle for anything over ...say...40 ohms has always defeated me.
I would also point out that I have never accepted the single RCD on a TT....there should be a requirement for a 'master' 100ma T/D alongside the 30ma device unless it can be proved that an Ra value low enough to operate an OCPD can be maintained.
Bear in mind as well that most of the TT queries on this forum concern small installs....(not the kind of big stuff E54 deals with)....for which multiple super rods are overkill IMO

 

[Engineer54]

I've been ploughing a relatively lone furrow on exactly this point on here for ages....and taken a lot of flack for it.
The logic of those who scoff at the Bs recommended max of 200 ohms,and then smugly state they wont settle for anything over ...say...40 ohms has always defeated me.
I would also point out that I have never accepted the single RCD on a TT....there should be a requirement for a 'master' 100ma T/D alongside the 30ma device unless it can be proved that an Ra value low enough to operate an OCPD can be maintained.
Bear in mind as well that most of the TT queries on this forum concern small installs....(not the kind of big stuff E54 deals with)....for which multiple super rods are overkill IMO

The flack came and rightly so, from you advising junior members to bung a twig in the ground and if you saw 200 ohms or less, that's all you needed for a TT system, and not bothering any further...

I think that i have stated many times now that as far as domestic installations go, a couple of coupled 5/8'' rods (coupled) should be the standard installation, coupled with an up-front S type RCD device. Do you really think that's over the top, considering that the TT installation you have installed should be robust enough to last a min of 30 to 40+ years??

Now let's say that driving 2 rods in the ground on a domestic installation gave you an Ra value of say 10 ohms. You know that in all probability, the stability is going to be present. Would you approach the client and give them a choice of adding another rod, thus getting down, pretty much close to the 1 ohm mark (after settlement) or not?? Which is the other point i've been trying to make over the many threads on this subject... Wherever or whenever possible, go that extra distance to get the desired results, and not just rely on what it says in the Reg's...

As for commercial and industrial installations that have a number of employee's etc why wouldn't you be trying to aim for TN values?? A 200 ohm's max in such circumstances, is complete tosh!! Oh, ...and what you call ''Super Rods'' were once the standard sized rods used in the UK and everywhere else and STILL ARE, in most of the countries i've ever been.... I actually saw for the first time, a 1m 5/8'' rod while in an electrical wholesalers in Cyprus while i was home a short time ago. I asked if that was the standard size they were using now in Cyprus. ...What i got was a blank look, he then disappeared out back and came back with a what looked like a 2.4m rod, ''first one of these, ...then one of these'', pointing to the 1m rods!!! So even in Cyprus the one metre rod is classed as no more than an extension piece!! lol!!!

 

[Engineer54]

And you can install a purrrrrrfectly good earth rod?

How do YOU know?? lol!!!

 

[Top Cat]

How do YOU know?? lol!!!

Maybe he's clairvoyant the same as you!

 

[Engineer54]

Maybe he's clairvoyant the same as you!

Yep, ...must be!! lol!!