Testing Ze for a new consumer unit in a garage

[Manator]

MET: Main earthing terminal, The terminal or bar provided for the connection of protective conductors, including protective bonding conductors, and conductors for functional earthing, if any, to the means of earthing.

The above definition is taken from the book, it does not state at any time that this MET should be at the point of supply, nor does it say that it can not be placed at any point within, or even shared with, any other point of the installation.

 

[steptoe]

where is it supplied from?

each and every electrical installation shall be fed seperately from every other installation.

 

[Sidewinder]

No Plumber you have NOT.

IF you have a reg to back up your position then you should NOT need to type a whole section out.

I am off to bed shortly and do not have the brb here.

I have a job tomorrow where I am incommunicado and the same applies for at least the mornings for the next 4 - 6 working days.

The NOMS do not take kindly to communication devices taken onto their premises, & I don't want a bed for the night or longer!!!

I will look into your claims and respond as I have time.

However, your lack of justification of your argument seems to me lack of either your understanding or your belief.

You should not need to type complete section of 7671 out to explain your situation.

 

[Chr!s]

No Plumber you have NOT.IF you have a reg to back up your position then you should NOT need to type a whole section out.

I am off to bed shortly and do not have the brb here.

I have a job tomorrow where I am incommunicado and the same applies for at least the mornings for the next 4 - 6 working days.

The NOMS do not take kindly to communication devices taken onto their premises, & I don't want a bed for the night or longer!!!

I will look into your claims and respond as I have time.

However, your lack of justification of your argument seems to me lack of either your understanding or your belief.

You should not need to type complete section of 7671 out to explain your situation.

Lack of justification? How do you arrive at this, i suggest when you have time, read the posts and REGS stated with thr BRB to hand and then state where the lack of justification is.

I look forward to your justification which along with Manators is non existent as it stands.

So lets see how my lack of understanding stacks up to your apparent understanding on this issue.

I look forward to your response.

 

[Manator]

I have just fallen off my chair laughing. You are having a laugh are you not? You are not being serious? Sorry if you are serious, I just wanted to check, before I move this to the student and learning section.

Anyway I have nothing better to do for a while so I will try to clarify.

Yes So the cpcs in the shed connect to what?

A MET Yes

What connects the MET to the means of earthing?

A earthing conductor. Yes

How many earthing conductors can an electrical installation have?

1 As many as required, depending on the installation

So as far as BS7671 is concerned, the shed is an electrical installation in its own right.

In the same way you could divide and call all parts separate

How many people veiw it that way?

Very few

Are you wrong for viewing it that way as ADS has

NO

If you think yes Back it up Please!!!

If you are insisting that it is a separate installation, then lets look at the REGS.

541.2

The earthing system of the installation may be subdivided, in which case each part thus divided shall comply with the requirements of this chapter.

542.1.8

Where a number of installations have separate earthing arrangements, any protective conductors common to any of these installations shall either be capable of carrying the maximum fault current likely to flow through them or be earthed within one installation only and insulated from the earthing arrangements of any other installation. In the latter circumstances, if the protective conductor forms part of the cable, the protective conductor shall be earthed only in the installation containing the associated protective device.

Now you could argue that you have stated that this forms the basis of your statements, however you have also argued that the Ze for this new consumer unit, is taken from that CU, it is not, Ze is, and always will be external to the supply.

Let me explain a little why this should never be confused.

If you design any installation some factors you will always need is type of earthing, type and size of supply and the expected or design loading of the supply.

Ze is a fixed measurement that is provided by the DNO, this figure given for TNC-S/PME is 0.35, and for TNS 0.8. You can not guess that these figures will be lower, but you can reasonably assume that it can not be higher. These figures are the figures used to design all large installs.

Now we have another problem, with any TNC-S the neutral conductor is still connected to earth, so why have we just banged a rod in?

Well, its all about potentials, and the differences this could cause, another reason why multiple rods are placed so that the potential from one does not effect the potential of another.

So what is this reading at the new CU? if its not Ze? Well if the CU is not at the origin of supply we must call it something else, simply because we have to treat this extension of the installation as part of the same system. It is earthed at multiple points, next time you extend a TNC-S, have a look at the readings you get to neutral.

Unfortunately the model forms, do not include all the information you would need to successfully complete a full EIC. Which is why some scheme providers have their own EIC forms, so that the details I have mentioned above can be correctly filled in.

 

[Sidewinder]

Plumber,

Are you not familiar with the H&S legal system in the UK

It is the duty of the accused to prove their innocence.

Thus it is down to you to prove that you are correct, as you are in the dock mate, and you are the accused, as I said earlier in my posts in this thread.

You need to bear this in mind when you come up against Professional Engineers when you are in the dock as they will be acting as the professional witnesses for HSE, and IF you are up against HSE in a case like this then it is more than likely that their inspectors will be Electrical Engineers, as I know personally many of their electrical specialists are, and it would be a specialist who would prepare the case against you.

I will review the evidence in my prosecution case, however, it is in law your responsibility to prove that your case for the defence is adequate and shifts the blame from the accused ; )

In case you were not aware the "innocent until proven guilty" premise of UK law is reversed in H&S law.

Note to Steve: There are exemptions,I know, as there are in all laws, however, this is the general case, and, it may fall on the accused to disprove this would it not!

 

[kme]

I`m really having difficulty believing this "discussion" is still taking place.

.......

Actually, on second thoughts - I don`t suppose I should be surprised. But here`s my understanding of the basics of this:

1. the outbuilding (or whatever) cannot be "a seperate installation", as it is fed from the "main board" (or another sub-board), of the property concerned. Therefore, it IS part of the installation formed by the board at "the origin" ( lets say, for the sake of argument, that is where the meter is). Just because we`ve provided a seperate type of earthing, you are suggesting it becomes a seperate installation???? Really???

2. The points about "multiple" METs, ECs, etc. Suppose you`ve got a TT with a carp reading, and you sink a seperate rod (or maybe multiple rods). The conductors from those rods are what? Are we saying that ONE of them is an EC, and the others are "something else"? Or are they ALL Earthing Conductors? As for the outbuilding earthing terminal, I`d have said it was a BEMT.

3. The means of earthing "exported" (and discarded at the outbuilding) provides the Zs of the distribution circuit, for the schedule of the supplying board. Apart from that reading, and the R1+R2, the discarded conductor is of no further use, except its purpose:to protect the sub-main cable itself. The schedule for the outbuilding (test results) gives Zs and Ipf boxes at this distribution board. Since the CPC of the sub-main has been discarded, and is not electrically part of the outbuilding, the Zs reading would be the result obtained from the test. When prevfiously doing this, I`ll make an extra note in this box, that the sub-board is a TT - though, as said earlier, it should be obvious to anyone reading the cert.

KME

 

[Sidewinder]

KME,

This is why I have approached this discussion with the point of view I have!

I cannot comment any more at the risk of putting myself in a situation where by I am in contempt of court!

 

[NozSpark]

And there was "little old" me thinking that an installation started at the origin, and that the origin was the suppliers fuse(s) and meter.....

I'm neither little nor old,,, sidey and steps can confirm that

 

[Sidewinder]

Mind Noz, old is getting there!!! ] :x

 

[ADS]

...... however you have also argued that the Ze for this new consumer unit, is taken from that CU, it is not, Ze is, and always will be external to the supply.

Wrong - Ze is the EFLI external to the installation - NOT the supply.

Ze - That part of the earth fault loop impedance that is external to the installation. (BS 7671)

Electrical Installation (abbrv. Installation) An assembly of associated electrical equipment having co-ordinated characteristics to fulfil specific purposes. (BS 7671)

No mention of origin, supply, cut-out or anything else!

So the Ze of the 'outbuilding' installation is taken at the 'outbuilding' CU/DB.

Ze is a fixed measurement that is provided by the DNO, this figure given for TNC-S/PME is 0.35, and for TNS 0.8.

So, what about TT??

So what is this reading at the new CU? if its not Ze? Well if the CU is not at the origin of supply we must call it something else, simply because we have to treat this extension of the installation as part of the same system.

Wrong again - It's Ze of the outbuilding installation..........and it's not part of the same 'System' - the main 'installation' is TN, the 'outbuilding' is TT

The outbuilding is an installation within it's own right having it's own 'earthing system' - unless you utilise the 'earth' from the original installation.....then the outbuilding would be an extension of the original installation.

I really don't see how you can argue against this.

 

[Sidewinder]

ADS,

Your arguments would not stand up in a court of law mate, please revise!

 

[ADS]

ADS,Your arguments would not stand up in a court of law mate, please revise!

Why would I be in a court of law over whether an outbuilding was a seperate installation??

Or the fact that I issue a seperate EIC for an outbuilding??

My arguments stand up here - and that's all that matters.

---------- Post Auto-Merged at 00:06 ---------- Previous post was made at 00:05 ----------

Can you contradict anything in Post 57??

 

[Manator]

I will emphasise one word

NEUTRAL

 

[Sidewinder]

ADS,

As usual my point is totally missed by yourself and many others here.

I am bored and tired with your games and off to bed.

Not even sure if I will bother with posting again as per my earlier comments.

If this cannot be grasped then what chance have you, when it goes wrong, & you are up against specialist professional witnesses who are determined to see you go to jail?

I don't necessarily post here wholly for my benefit.

 

[ADS]

Sidewinder, I have no idea what you are going on about - but if you are to be taken literally, then noone would discuss anything on here!!

---------- Post Auto-Merged at 00:18 ---------- Previous post was made at 00:15 ----------

I will emphasise one wordNEUTRAL

Manator, the NEUTRAL has no bearing on this discussion whatsoever - probably because our outbuilding is a seperate, TT, installation.

 

[steptoe]

yes it has ADS,

if you cannot grasp this then Im worried,

do you understand what TN & TT stand for?

 

[Manator]

He probably refers to CJCPIE Protocol 13, ADS, there is a fundamental flaw in your argument, just like that from Plumber. Full understanding of the regulations not only those as per BS7671, but others, will have a direct bearing on what you are trying to say.

Yes I did say supply, but as you pointed out, the definition is indeed installation. However I said supply so as not to confuse the issue and imply that I now agreed that it was a separate installation. The key with this argument is the neutral conductor.

 

[ADS]

yes it has ADS,if you cannot grasp this then Im worried,

do you understand what TN & TT stand for?

Steptoe, please don't start questioning my knowledge again - this thread is running quite smoothly up to now - I think I give a good enough account for myself that we don't have to resort to this again.

Can you explain what relationship the Neutral conductor has as to whether the 'outbuilding' is classed as a seperate installation or not??

 

[Manator]

The neutral conductor taken to the outbuilding CU, is still earthed as in it is effectively now a TNC. This is the reason why it is so important.