Discuss how to upgrade the earthing conductor? in the Industrial Electricians' Talk area at ElectriciansForums.net

calm down guys, let me explain before you get further, i certainly know the difference between the two systems, but when you are on site, it is difficult to tell the difference between them, i know you guys are very experienced, but from on site guide i dont think it is very obvious and enough to make everyone can identify them immediately, so why not be more patient and more constructive?

Can I ask what training and experience you have mate?
And what reference documents you have access to?

If you understand the difference between earthing systems then identifying them shouldn't be a problem, unless you have a DIY PME of course.
 
????? where's that from?

OSG. There is a table near to the front (wish my books weren't in the van.) that gives guidance on the earthing conductor size in comparison to the size of the incoming neutral which states it should be half the csa size of the neutral and in the case of PME 16mm min.
I'm pretty sure that right off the top of my head.

Also, if you were upgrade the earthing conductor would you have to contact the DNO as it's attached to their side of the incoming? I've raised this point on a separate thread and weren't given the same answers.
 
Also, if you were upgrade the earthing conductor would you have to contact the DNO as it's attached to their side of the incoming? I've raised this point on a separate thread and weren't given the same answers.

Good question. Technicality would say you should. I can only vouch for Western Power Distribuition, who say that if it's a sweated joint it's their responsibility, but if it's an earth clamp, it's yours and you can do what you want with it.
 
OSG. There is a table near to the front (wish my books weren't in the van.) that gives guidance on the earthing conductor size in comparison to the size of the incoming neutral which states it should be half the csa size of the neutral and in the case of PME 16mm min.
I'm pretty sure that right off the top of my head.

Also, if you were upgrade the earthing conductor would you have to contact the DNO as it's attached to their side of the incoming? I've raised this point on a separate thread and weren't given the same answers.

You are kind of correct however it isn't the minimum. Reg 543.1.1 states that the sizing of every protective conductor (other than protective bonding conductors) shall be:

i) calculated in accordance with regulation 543.1.3, or
ii) selected in accordance with regulation 543.1.4

Calculation is done with the adiabatic, and this is how you will determine the minimum cross sectional area, and so it isnt 16mm. I highly suspect that if the calculation is done, then the existing earthing conductor will be more than adequate.
 
Last edited:
OSG. There is a table near to the front (wish my books weren't in the van.) that gives guidance on the earthing conductor size in comparison to the size of the incoming neutral which states it should be half the csa size of the neutral and in the case of PME 16mm min.
I'm pretty sure that right off the top of my head.

Also, if you were upgrade the earthing conductor would you have to contact the DNO as it's attached to their side of the incoming? I've raised this point on a separate thread and weren't given the same answers.

On site guide page 28 table 4.1 requires that 16mm,25mm and 35 mm tails have 16mm earthing conductor not buried
note 2 the distributor may require a minimum size of earthing conductor at the origin of the supply of 16mm copper or greater for tn-s and tn-c-s
10mm main protective bonding conductors to extraneous conductive parts

when i read the post he had wrote considering upgrading
6mm earthing conductor to 10 mm earthing conductor which he has now changed to 16mm

I also asked if he was carrying out just a pir or additions or alterations but also more importantly meant to say new installations ccu upgrade

If it was just for a pir then he should make observations and recommendation codes for the devations from the regs that he finds

but he said TN-C-S but the description sounded like a TN-S so i advised him to seek advice from the DNO as to what system and requirments

the osg on page 17 for a tn-c-s system states minimum 25mm tails so the earthing would have to be 16mm
 
Last edited:
I called the nic technical once after another spark told me i was wrong for leaving 16mm tails and 10mm main earth in service on a 60a tn-s supply when changing a consumer unit, my argument was that the cut out fuse was only a 60a and via calculation these tails an earth were fine then he showed me the page in the osg stating no less than 25mm tails 16mm earth, anyway nic told me i was in the right and osg is presuming its a new installtion in which case would most likely be fused at 100a or greater, and that sizing via calculation is fine. you dont always get the same answer from the technical line it varys form whos answering the question normally.
 
If in doubt, cosult the regs. The OSG is there as a quick approximate reference. Otherwise, what would be the point in having a big red book.
 
If in doubt, cosult the regs. The OSG is there as a quick approximate reference. Otherwise, what would be the point in having a big red book.

Excellent advice, many say the reg's are ambiguous but they allow the use of engineering principles rather than a black and White thou shall or shalt not.
The adiabatic is a perfect example and anyone carrying out periodic inspections should be familiar with it.
 
calm down guys, let me explain before you get further, i certainly know the difference between the two systems, but when you are on site, it is difficult to tell the difference between them, i know you guys are very experienced, but from on site guide i dont think it is very obvious and enough to make everyone can identify them immediately, so why not be more patient and more constructive?

Fella, let's make something pretty clear right off.

The term "just finished an inspection" implies that you have just completed a periodic inspection on a system. In oder to have done that, the general level of experience would be something around the level of C&G 2391.

To obtain C&G 2391, you would certainly know how to tell the difference between one earthing arrangement and another - that's basic stuff.

It is NOT difficult to tell the differences between an earthing system either on site, or from the OSG - the differences are VERY clear, and for good reason. Again, it really is BASIC stuff.

Most of your respondees have been very patient with you. And they have asked especially constructive questions, given that one key requirement for an electrician engaged on test and inspection is the ability to think, and to reason through a given situation.

There's another angle to this.

Wandering in with the view that on the face of things you're claiming a knowledge on one hand, that your statements aren't backing up on the other, is only going to get you incredulous responses.

Had you come in and said something like "Fellas, I'm out of my depth here - I've been asked to complete a PIR and I haven't got a clue how to do it" would have got you far more helpful responses, since that's the impression you have ACTUALLY created, in any case, but with the emphasis on blagging a test which could have potentially disastrous, if not fatal results if wrong.

Page 15 of the OSG shows you a TN-C-S system VERY clearly, in colour, and the other two systems you're likely to come across are equally clearly shown on P16.

If you actually look, you can see the differences. And they are clear.

It isn't to cause offence that people are asking what qualifications you actually have. Mostly, that's for YOUR safety, and that of your customer. Would you throw a hissy fit if we shouted at you when you were about to fall off a ladder, or electrocute yourself?

I'll ask you a simple "what-if" question here to highlight what I mean about danger.

What if you carried on and disconnected that supplier earth in preparation to upgrade it - for any reason.

What if, as is likely, the supplier cut out is locked and tagged against unauthorised removal - so you don't remove it, leaving the installation live. After all, it's only an earth, right?

So, what if, while you've got that disconnected, a fault you missed further on in the installation causes all the shiny stainless steel metal work in the bathroom to go live, just as the owner of the house is getting out of the bath they were taking to keep out of your way? Where is their towel? On the shiny exposed metal towel heater. And they're touching it with wet hands and body.

What do you think happens next?


THAT is why we take what we do so seriously. That is why, when someone comes in claiming a certain level of knowledge (inspection and testing) and then falls over on fundamentally basic points, alarm bells ring loudly. And that is why, as professional electricians, we act with pretty well one voice in the way we do.

Perhaps, then, you can leave the hurt and indignation aside for a little while, and be honest about your actual skills and qualifications. Then you might just get the advice and help you need. For everyone's safety.

Do you actually have an on site guide, or BRB, by the way?
 
If in doubt, cosult the regs. The OSG is there as a quick approximate reference. Otherwise, what would be the point in having a big red book.

Totally agreed. As stated before, ultimately, the OSG is INTERPRETATION of the regs, which in themselves can be subjective and open to interpretation in places. Where ANY doubt at all exists, the word of the BRB shalt be the whole of the law.

Most DNO's I've come across have also stated sizing by calculation and distance, with a preferred minimum of 25mm tails on NEW installs, verification of existing on CU changes by calculation.
 
The information is not a secret,but the understanding of the system should be fundamental to any electricianL
limitations are what safety is about, Diyers should limit their work to the level of their understanding
Once they exceed that understanding,any work they carry out could be dangerous
Informing the ignorant of ways to end their existance may not be a sensible action
 
Going back to a point raised earlier gents.
Are we saying it's acceptable to leave the current earthing as is it and reterminate in a MET and link into the CU with 16mm.
Or
Apply the adiabatic equation and work out if it is acceptable according to this.
I'm with brucelee on this one. Yes the OSG is a guide, hoeever there must be reason behind stating these figures in the first place backed by knowledge and reasoning from the regs.
 
That will be a tn-s system and is the suppliers earth to met, so providing you have a ze lower than 0.8 ohms and the consumers earth from the met to the consumer unit is of an adequate size its of no concern to your pir. If on the other hand the small wire is coming straight off the sheath into the consumer unit i usually reterminate into an external met and take a 16mm into the cu it will then satisfy the cert as the consumers main earthing conductor is of the right size. you should neva mess with there incoming cable, if you take a ze reading and it doesnt satisfy you contact the supplier to upgrade hope this may help.

If I was doing a PIR and there was a 6.0mm earth from the cutout to the MET and then a 16mm to the CU,the earth size on the cert would be 6mm, not 16mm.....the 6.0mm will have to carry the same fault current as the 16mm.
 
As I've already stated, sizing of protective conductors is by either SELECTION or CALCULATION!!
If it's a new installation then selection can be applied at the design stage. This chap has attended an already existing installation and is thinking about upgrading the earth when it most likely is not necessary.

If you don't know how to do the adiabatic then say so!!!


Sent from my iPhone using Tapatalk
 
just to come in on this at a late stage on what has obviously been an interesting discussion. It should be remembered that unnecessarily upgrading earths could potentially cause problems in itself as this could lead to higher PEFCs that might exceed the breaking capacity of the protective devices so they can not clear the fault safely. It really should be checked properly and not just immediately assumed that bigger must automatically be better.
 
just to come in on this at a late stage on what has obviously been an interesting discussion. It should be remembered that unnecessarily upgrading earths could potentially cause problems in itself as this could lead to higher PEFCs that might exceed the breaking capacity of the protective devices so they can not clear the fault safely. It really should be checked properly and not just immediately assumed that bigger must automatically be better.
i may be inaccurate here, but theoretically the protective device, usually a 1361, will blow long before the fault current gets anywhere near it's rated breaking capacity of 16kA. it's a very rare occurence for a fault current to develop upstream of the circuit protective devices, although not unknown.
 
Last edited:
As I've already stated, sizing of protective conductors is by either SELECTION or CALCULATION!!
If it's a new installation then selection can be applied at the design stage. This chap has attended an already existing installation and is thinking about upgrading the earth when it most likely is not necessary.

If you don't know how to do the adiabatic then say so!!!


Sent from my iPhone using Tapatalk

Fair comment.
But selfishly let me take another view.
A few months ago I started a thread similar to this where I went to a customers house.
British gas where to install a new central heating system but refused to do it cause the main earthing conductor was 4mm straight into the MET on a TNS system.
I'm still in the process of awaiting DNO to come out so it can be changed over.
Now although the Ze was fine and PFC I questioned the inadequacy of the size that would it take the fault current. Would this mean I shouldn't be changing this too and telling British Gas to stop being so silly?
 
Fair comment.
But selfishly let me take another view.
A few months ago I started a thread similar to this where I went to a customers house.
British gas where to install a new central heating system but refused to do it cause the main earthing conductor was 4mm straight into the MET on a TNS system.
I'm still in the process of awaiting DNO to come out so it can be changed over.
Now although the Ze was fine and PFC I questioned the inadequacy of the size that would it take the fault current. Would this mean I shouldn't be changing this too and telling British Gas to stop being so silly?

It would depend completely on the calculation. I can't say yes or no without knowing more.


Sent from my iPhone using Tapatalk
 

Reply to how to upgrade the earthing conductor? in the Industrial Electricians' Talk area at ElectriciansForums.net

Similar Threads

I'm practising EICRs on friendly locations as I'm still in training - technically done my 2391-52 but frankly need loads more practise. I've just...
Replies
11
Views
814
Hi, I have a Victron Multiplus-II 5kVA inverter/charger with Pylontech US5000 batteries installed in my house along with a 6.8kWp PV array and...
Replies
12
Views
445
Hi guys, I hope you're all doing ok in this heat!! I have recently carried out an EICR on a domestic property where it failed miserably. The...
Replies
6
Views
6K
I've come to a decision, I just cant do work anymore that involves mad stuff, for example today - 2 bed flat that's had fire damage, someone has...
Replies
4
Views
828
Just a bit of a muse at the moment, work won't happen for a while, though I do already have the ducting. We have (what's left of - it was rotten...
Replies
0
Views
1K

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc
This website was designed, optimised and is hosted by Untold Media. Operating under the name Untold Media since 2001.
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock