Another Earth Rod or Export from MET?

[oldAL]

yep, but the 'bible' as you call it isnt really law, is it?
yes, I know we all work to it, but that doesnt make it ok to do something that 'may' be dangerous.
I see no issue with providing your own rod/s and really making sure it is almost a PME system, personally I measure all of the 'PME' systems I work on and add a rod if I think it is needed.

 

[Jimmy Boy]

yep, but the 'bible' as you call it isnt really law, is it?
yes, I know we all work to it, but that doesnt make it ok to do something that 'may' be dangerous.
I see no issue with providing your own rod/s and really making sure it is almost a PME system, personally I measure all of the 'PME' systems I work on and add a rod if I think it is needed.

Nope indeed, but it is what a lawyer would use to defend you with if you got in hot water, try the defence of knowing better than the regs book, you will soon be kicking the soap around the shower room

 

[oldAL]

you could always try EAWR16, and that is the law.

 

[Engineer54]

E54,
this is the exact point you fail to grasp, just because the DNO calls it PME doesnt mean it is, there are far more TNCS systems out there than proper PME,.

I Don't know about the area where you are from, but that's not the case as far as a just retired DNO area manager....

Most TNC-S systems are ''In Progress'' TN-S systems being converted to PME, often supplying both TN-S and PME service cut-outs. These in progress systems can also have a slightly higher Ze value, as i'm told anything around 0.50 to 0.60 ohms. Still a dammed sight better value than relying on a 1m twig at 200 ohms and a possible dodgey RCD device!! lol!!

 

[Jimmy Boy]

I Don't know about the area where you are from, but that's not the case as far as a just retired DNO area manager....

Most TNC-S systems are ''In Progress'' TN-S systems being converted to PME, often supplying both TN-S and PME service cut-outs. These in progress systems can also have a slightly higher Ze value, as i'm told anything around 0.50 to 0.60 ohms. Still a dammed sight better value than relying on a 1m twig at 200 ohms and a possible dodgey RCD device!! lol!!

As I said in an earlier thread I have overhead TNCS I assume but am not sure that it is true PME I will measure my ze alter in the week would a 'true' PME/TNCS give me a reading considerably lower than 0.35 ?

 

[Engineer54]

As I said in an earlier thread I have overhead TNCS I assume but am not sure that it is true PME I will measure my ze alter in the week would a 'true' PME/TNCS give me a reading considerably lower than 0.35 ?

You'll find that most, if not all overhead PME supplies are just that, ...True PME!!
Overhead supplies are the easiest distribution systems to PME. To confirm, you should be able to see an earth/neutral connection at every third pole!!!

 

[Jimmy Boy]

I will go and have a look and take a pic !

 

[Engineer54]

Rural and semi rural overhead distribution supplies were the first systems to be PME'd, to give the then many TT households a TN earthing system that most towns and cities enjoyed. The then electrical boards spent millions converting thousands upon thousands of such systems...

Now we have new and/or brainwashed electricians creating new TT systems to replace a perfectly good PME earthing a the drop of a hat, because they believe all the crap and scaremongery that abounds!! It wouldn't be so bad, if they knew what they were doing in creating a TT system, but the truth is, more often than not they DONT!!

 

[Guitarist]

Anyone know if there is a charge to TNC-S an old TT system? Quite a few around my part of the world with all kinds of things used as earth electrodes.

 

[Engineer54]

As far as i'm aware, if the supply to which your presently connected is a working PME system then there should be no charge. But i'm afraid there are many of the new DNO operators that see this as another money making service for them, and forget all about the standing charges that are supposed to cover such upgrades etc!!

So the correct answer is that some DNO's charge and some Don't!! lol!!

 

[Guitarist]

As far as i'm aware, if the supply to which your presently connected is a working PME system then there should be no charge. But i'm afraid there are many of the new DNO operators that see this as another money making service for them, and forget all about the standing charges that are supposed to cover such upgrades etc!!

So the correct answer is that some DNO's charge and some Don't!! lol!!

Thanks for answering Eng. I will give UKPN a ring and see what they say.

 

[jreg]

My thoughts are that if the garage 20m away is connected to the MET from the dwelling surely this extends the equipotential zone to the garage
I have a situation where the garage/workshop is fed from the meter box on the dwelling via 16mm2 SWA & 30 ma RCD with 1 core of the SWA plus armour connected to the MET. This extends the earth to the garage.
In a TNCS installation, if there is a neutral break then the RCD to the garage would trip as it would see an unbalance between L & N and dis power from the garage.
I feel that if you were to install a TT system in the garage, you would still have to bond the heating boiler pipes in the garage to the garage earth. Now these heating pipes are already bonded to the main buildind MET which is still exporting the TNCS earth in spite of the TT installation in the garage. I would be interested in what others think of this idea

 

[Engineer54]

Where utility services serve or pass through more than one building, the same earthing and bonding arrangements should be applied to all buildings.

You can compare that ruling, with say a row of houses all served by the same water and gas mains, or in multi storey blocks of flats/apartments etc!! Those common service pipes will still be required to be bonded at every premises... lol!!

The only time i would leave a PME earthing system behind, is where it becomes uneconomical to extend the existing equipotential zone. (eg, distance over cost of providing minimum bonding conductor)

 

[Guitarist]

A little update on the TT situation....

Phoned DNO to ask about the conversion last Thursday.... "Well, it is free, but the power guys will have to actually carry out the work".
Phoned power guys....."Yes, we can do that for you. I will send someone out this afternoon."

I explain again that it isn't an emergency, just a conversion. "No problem." says the guy.

That afternoon power guy turns up and I explain the situation.... "Sorry, we don't do the conversion. Your DNO have to do that. I will check the EFLI while here though".

Power guy pops in a new neutral block which will accommodate the 16mm earth and gets a nice 0.36 ohm reading. Really nice bloke, very polite and helpful, wishes me all the best.

Phoned DNO yesterday to get it connected, and they insist that it's the power guys who are responsible. Power guys closed due to emergency call-outs....

So, no further forward at this point

 

[Engineer54]

Orchestrated Chaos reigns supreme then!! Nothing much changed there then... lol!!

At least their not charging you for the privilege!! lol!!