TT system.

[green-hornet]

Cheers GHGrounding compound. Have seen this being used on mats connected to lightening conductors. Never used it myself. Where would I purchase this from? As I did have to drill to get the rod down.

There is a link above kindly posted by netblindpaul

 

[Andy™]

Evening all.Did a job today involving running a sub main supply to an outbuilding at a tourist centre. Earthing arangements at the main switch room where TNC-S. Therefore earth not exported and a 1200mm earth rod was installed.

The Earth loop reading I got at the DB was 694ohms. What would be the best way to reduce this to below 200ohms?

The ground is mainly slate below for a fair few meters.

Cheers. J

have you tried Russ andrews method?

One of the problems of using an earth spike is that it is sometimes very difficult to drive a 4ft (1.2m) spike deep into the ground! The copper-clad steel rods supplied by electrical wholesalers often bend when driven into the ground

 

[gselectrical]

[quote name='Andy

 

[batty]

Russ who?! :^O

He was a comedian although maybe still is Russ abbot)

 

[steptoe]

Slate is impervious to water, hence used for damp proofing and roof slates, so chances are you will struggle even with a longer rod. Having said that if your on TNC-s which also relies on rods, there must be an area of ground that is useable so options for consideration.1/ bang in extendable rods (would try 2 and see what diffence it makes)

2/ look around for softer piece of ground further away from the building (perhaps head for the bank of a stream??

3/ try connecting to steel work of building, pipes, or the like and very carefully sign installation/ annotate certs that this has been done.

4/ Invent some new and creative technique unique to old slate quarries (can't drop a long cable down the mine shaft can you?? :coat )

Would also be worth consulting NICEIC, they might have some ideas. Would also discuss the max rod impedence which in theory can be upto nearly 1667ohms. Have a good re-read of section 4 of the regs.

You might also be able to justify high Zra if it is stable, so might mean returning over a few weeks of variable weather to demonstrate that rod resistance doesn't fluctuate with the weather - avoidance of which is the basis of the 200/500ohms recommended max.

where have got got that nugget of wisdom?

TNCS is NOT PME

pme must always be TNCS, but it is not an exclusive two way deal,

tncs need not be pme.

 

[ADS]

where have got got that nugget of wisdom?TNCS is NOT PME

pme must always be TNCS, but it is not an exclusive two way deal,

tncs need not be pme.

Steptoe, you really are annoying

Everytime someone mentions 'TN-C-S' and 'PME' in the same sentence you have this same rant.

Now is the time to come clean - let's see how clever you really are

One question,

What else can TN-C-S be, then?

 

[Andy™]

What else can TN-C-S be, then?

CNE. only 1 rod at star point.

this has been mentioned many times on many threads

 

[ADS]

[quote name='Andy

 

[Andy™]

Unfortunately, incorrect. CNE (Combined neutral and Earth) is just another name for PME.

Lets wait and see what Steptoe has to say

not fully... CNE 'could' be used to describe PME, in that both use neutral for the earth

only PME is used for general distribution, as CNE only has 1 rod at star point. CNE may be used when a place has its own transformer

 

[ADS]

[quote name='Andy

 

[Andy™]

So is there really any reason to rant on every time someone mentions the two together?? ; \

id say 99.9% of the time TNCS is mentioned,it refers directly to PME, and not CNE or any other variation

in the odd post where CNE is specifically required, then person would most likely be aware of that, and say what they mean, and not just 'TNCS'

 

[ADS]

Agreed, so if I (or anyone else) am talking about TN-C-S on a thread, and refer to it as PME, then the likelihood is that it is PME, so there is no need for Steptoe to continuosly interupt threads with the comment 'TN-C-S IS NOT PME'

WE KNOW!! WE GET IT!!

.

 

[spinlondon]

We live in Gt. Britain.

BS7671, states within the definition of TN-C-S:

"This type of distribution is also known as protective multiple earthing."

CNE as far as I'm aware is another term for TN-C.

Stating that the distribution of TN-C-S can sometimes be CNE is the same as stating that it can sometimes be TN-C.

A ridiculous statement, as the distribution of TN-C-S is allways TN-C or CNE whatever term you choose to use.

Also as far as I'm aware, even on the very rare occaisions where a TN-C system is used, the distribution is still PME.

I am well aware that they use other means of distribution abroad, but as all of these statements regarding TN-C-S and PME seem to refer to installations within Gt. Britain, shouldn't we use the definitions provided in the Regulations that apply to Gt. Britain?

 

[Andy™]

We live in Gt. Britain.BS7671, states within the definition of TN-C-S:

"This type of distribution is also known as protective multiple earthing."yes, but TNCS is not always PME. as alreayd stated, it can take other forms

CNE as far as I'm aware is another term for TN-C.pretty much

Stating that the distribution of TN-C-S can sometimes be CNE is the same as stating that it can sometimes be TN-C.

A ridiculous statement, as the distribution of TN-C-S is allways TN-C or CNE whatever term you choose to use.yes, but there are differences. in that PME has multiple rods, other types only have 1 rod

Also as far as I'm aware, even on the very rare occaisions where a TN-C system is used, the distribution is still PME.again, not always PME. may only have 1 rod

I am well aware that they use other means of distribution abroad, but as all of these statements regarding TN-C-S and PME seem to refer to installations within Gt. Britain, shouldn't we use the definitions provided in the Regulations that apply to Gt. Britain?for the most part (and like i said above), almost everything said on this forum, then yes. but other earthing arrangements do exist, although they are not often used, and where they are, its normally under special circumstances

my red

 

[spinlondon]

yes, but TNCS is not always PME. as alreayd stated, it can take other forms,

yes, but there are differences. in that PME has multiple rods, other types only have 1 rod.

again, not always PME. may only have 1 rod

Your Red.

Not according to BS7671.

 

[ianmacd]

Which part and where?

 

[spinlondon]

Part 2 Definitions.

 

[ianmacd]

Part 2 Definitions.

You mean the part where it says its found in TN-C-S systems rather than is the same as? So what if you have a PME distribustion with a TN-S presentation or even TT?

 

[Andy™]

yes, but TNCS is not always PME. as alreayd stated, it can take other forms,yes, but there are differences. in that PME has multiple rods, other types only have 1 rod.

again, not always PME. may only have 1 rod

Your Red.

Not according to BS7671.

7671 does not cover distribution.

 

[gselectrical]

Having trouble getting any marconite or bentonite. Have tried the link Paul posted, E-mailed them, but no reply.

Has anyone any suggestions as to where I can get some of this? Preferably online, as I need it within the next few days!

Cheers for the help

GS