Earth Fault loop impedence results not matching up!!!

[wade88]

Hi guys,

I have just recently qualified and have taken up a job as a plant manager (general maintenance duties and repair work), and some electrical work is involved in the job. I initially got the job in the first place as a result of being a qualified electrician and so the work the company requires doing will now be done by me as their "in house" spark.

However, before i began to do anywork i asked to see all their previous certs and records of any work that had already been done....and so was handed a CD that was left for them by the chap who did their work previously. Upon inspecting his results and looking at what he had done, i noticed that on nearly all of his minro works certs and EIC's that the EFLI was never under 0.35 for the TN-C-S system that is present here? Please excuse my naivity as like i said i just finished a 7 week intensive sparly course in birmingham with RF training and am still learning!!

Can anyone shed some light on maybe why he hasnt contacted the supplier to correct this? On what may be causing this and how to reduce the resistance? Some of the readings he was recording were like 2.0 ohms! To me and from what i have been taught that is a ridiculous figure for a TNCS. Many other results are 0.60, 0.50, 0.78 etc, is it vital that the results are below the stated 0.35 or am i being naivie in thinking that in the real world outside of a classroom ,results may vary and are often uncorrectable?

Cheers guys, any advice or "slaps" for being a plum would be hugely apprecaited

 

[malcolmsanford]

First of all are you talking about the ZE or Zs for EFLI as that is a great difference.

The Ze for a TNC-S in the OSG recommends an ohmeric value of no greater then 0.35 ohms and for TN-S 0.8ohms. You only have 1 Ze and that is at the origin of the installation and if it's TNC-s I would expect it to be lower than 0.35 ohms. Now you may find that when this new work was done and the certifiactes were issued he may well not have been able to disconnect the main earthing conductor as your in an industrial enviroment and therefore unable to do this. I would have still taken the Ze to confirm the prescence of it, but becasue of the parrallel paths he may have put the value he did rather than a lesser one.

I personally would have also but a Zdb on my schedule of results as that is the Zs at the board he fitted the new circuit to.

The other values are most likely the Zs values of an individual circuit and they seem fine.

I now have to comment on how are 5 weeks on a get qualified quick scheme you will feel competant enough to run the electrical installation of a commercial/industrial situation?

 

[Sparky Ninja]

First of all are you talking about the ZE or Zs for EFLI as that is a great difference.

The Ze for a TNC-S in the OSG recommends an ohmeric value of no greater then 0.35 ohms and for TN-S 0.8ohms. You only have 1 Ze and that is at the origin of the installation and if it's TNC-s I would expect it to be lower than 0.35 ohms. Now you may find that when this new work was done and the certifiactes were issued he may well not have been able to disconnect the main earthing conductor as your in an industrial enviroment and therefore unable to do this. I would have still taken the Ze to confirm the prescence of it, but becasue of the parrallel paths he may have put the value he did rather than a lesser one.

I personally would have also but a Zdb on my schedule of results as that is the Zs at the board he fitted the new circuit to.

The other values are most likely the Zs values of an individual circuit and they seem fine.

I now have to comment on how are 5 weeks on a get qualified quick scheme you will feel competant enough to run the electrical installation of a commercial/industrial situation?

Agreed. I would expect we are talking Zs here.

 

[wade88]

How embarrassing, I meant the External Loop Impedence yes, the Ze. Not one of his results meet the figures comply with BS 7671, and having had a look, i can see no reason at all as to why he would not have been able to remove the main earthing conductor? This is what perplexed me initially.

Well your right, i qualified from the scheme in 7 weeks but this is seemingly the only way to go nowadays to get qualified. Given my circumstances it was the only way i could do it, and going on a 4-5 year apprentiship was simply not practical. However, i have little choice but to make best of such forums as this and tap up people like you for your experience as i have yet to develop my own. But i need to get on and just try my best at the job as i have a new family to to support etc. Ideally i would like to work alongside someone for 6 months and just watch you know to see how things are done but unfortunately no one seems interested in employing a mate at the moment so i have to go at it alone and do my best!....and squeeze you lot for help!

 

[Des 56]

Nothing personal.just a general opinion based on sarcasm

Perhaps an extra week or 201 weeks of training, before becoming a qualified electrician, would perhaps have been more adequate and it would also improve the terminology

I try and be sympathetic to the needs of modern trends toward training,but feel these courses are taking the p out of the electricians respect for their own trade


"7 weeks" I honestly feel dismay for this trade

 

[wade88]

Fair enough Des. And i apologise for any terminology i used that may have caused any offense. If you have a better solution for gaining such qualifications without going on "201" weeks of training, im welcome to hearing it. But in the mean time, im here looking for help not to be told how belittled you feel about the likes of me going on courses when im all im trying to do is earn some money to pay my rent and feed my family.

Im the first to admit that 7 weeks to learn such a vast amount of information is ridiculous and i never expected to walk away from the course with the intention of being Mr.Sparky, but the only way im going to learn anything is by getting on with it and leaning on forums like this for help.

 

[malcolmsanford]

How embarrassing, I meant the External Loop Impedence yes, the Ze. Not one of his results meet the figures comply with BS 7671, and having had a look, i can see no reason at all as to why he would not have been able to remove the main earthing conductor? This is what perplexed me initially.

Wade I do appreciate that you are trying to do the best for your family as I think most of the guys are doing the same. But your not helping yourself by not either thinking or showing a total lack of understanding.

There is only 1, repeat 1 Ze result and thare is no colation in the BS 7671-2008 regarding the Ze result. So are you therefore refering to Zs results?

As I outlined in my original post, which read again and decide what results are you not happy with the Ze or the Zs. If my explantion is not detailed enough then come back with a question that is concise and accurate.

 

[Des 56]

It wasn't intended as a personal attack, and belittled is not what I feel,outrage maybe that apprentices coming out of a full 3 or 4 years of hard graft on mostly low wages are having that effort undermined by quick fix solutions

I appreciate that at the end of the day,we all need to put bread on the table and you have succeded admirably in obtaining work with all of your talents. not just electrical probably
The point you made and I appreciate your honesty was that you had a lot to learn and was seeking some of that, by posting here

We all have a lot to learn and continue to do so,however long we have been practicing in the trade
You are employed,you are doing electrical work and you will be given the benefit of the experience and knowlege of many sparks on this forum ( as we all hope to gain)
I try myself to assist where I can and would do so where I can

I hope you do well in your job, and become as experienced as those you are asking questions of in the near future
Putting sentiments into the written word is difficult and sometimes what I write is understood differently to what was intended
Dont take offence with the post,it was a general opinion on the training companies and the trade and not a personal attack.if you saw it that way,I am sorry for that, and will apologise for any offence to you

 

[wade88]

Des i took no offense at all in what you wrote, i understand your point entirely. i have just finished a degree and unfortunately the direction that was taking me is no longer applicable to a career so i decided to dramatically change direction and learn a trade. And the only way to aquire the relevant qualifications given my age, situation etc was to do one of these intensive courses....which as Malcolm is helpfully pointing out...you forget very quickly if you dont keep working! Qualified maybe 8 weeks ago now and have been doing very little electrical work and have applied almost NONE of the skills and knwoeldge i learnt to a practical job anywhere. my megger is still in its box!

And its this im sure Des that probably pis*es you off the most is on paper im a qualified spark but in reality know about 5% of what i need to, to really operate properly, hence the reason we are sat here having this conversation.

Malcom, im not confusing the Ze with Zs in this instance, the results he has recorded state, the Ze is 1.05 ohms, the R1+R2 is 0.2 and the Zs is 0.6. This is a TNC-S system. I belive the approx calculation to aquire the Zs is Ze + (R1+R2) which would calcualte the Zs as being 1.25 not 0.6?

 

[malcolmsanford]

I see also your going to have a scheme assessment for doing domestic work so with running this production plant you are going to be kept busy.

The Ze for a TNC-S of 1.05 is far to high as you say and if that is correct you should be contacting your DNO to ask them why this is.

The R1+R2 of 0.2 is extremely unlikely, so he as either made a mistake or not done it.

The Zs of 0.6 cannot be achieved with a Ze of 1.05 and so again a mistake or he as not done it. Unless the place is so huge and the parallel paths have brought it down this low.

If it were me I would do a few tests of my own and see what is happening

 

[wade88]

Funnily enough he is in fact my next door neighbour so i may pop round and ask him! quite a few of his results do not look entirely legitimate so like you say he may well have made a few errors along the way or just made up a result.

Yes i am due to book in for an assessment, im thinking of going with elecsa as i have heard awful things about NIC and nappt require 2391 i believe. Any opinions on those? I feel miles of being ready for my assessment at the moment and need to get my head back in my regs book and revise like crazy to get back to sqaure 1! it feels a bit like learning russian at the moment!!

 

[Sparky Ninja]

Some of the readings he was recording were like 2.0 ohms! To me and from what i have been taught that is a ridiculous figure for a TNCS. Many other results are 0.60, 0.50, 0.78

So is this a large site with numerous origins?

Im the first to admit that 7 weeks to learn such a vast amount of information is ridiculous and i never expected to walk away from the course with the intention of being Mr.Sparky, but the only way im going to learn anything is by getting on with it and leaning on forums like this for help.

Is this the course you did?
You have chosen a training path that unfortunately will face a fair amount of criticism in comparison to some of the time served/trainee methods. I myself have issues, not with you trying to do what's best for your family, but with the training providers offering this method of training.
Could I please ask what particular qualifications you have obtained? And what opinion the training centre had of themselves and your future capabilities?
I must say though that of all these new 'express electricians' you have done one of the wisest things in joining us here and asking for opinions/advice.
Welcome to the forums and make yourself comfortable.

Malcom, im not confusing the Ze with Zs in this instance, the results he has recorded state, the Ze is 1.05 ohms, the R1+R2 is 0.2 and the Zs is 0.6. This is a TNC-S system. I belive the approx calculation to aquire the Zs is Ze + (R1+R2) which would calcualte the Zs as being 1.25 not 0.6?

If you see on a document a Ze greater than the maximum, and Zs values below the recorded Ze then take it for what it is. Then carry out these tests yourself as you've already come to the conclusion that they're not likely accurate.

Yes i am due to book in for an assessment, im thinking of going with elecsa as i have heard awful things about NIC and nappt require 2391 i believe. Any opinions on those? I feel miles of being ready for my assessment at the moment and need to get my head back in my regs book and revise like crazy to get back to sqaure 1! it feels a bit like learning russian at the moment!!

I would expect the 2391 to be required by all these, but I have little elecsa experience, I have been NICEIC for too long now and have done assessments on behalf of NICEIC and Napit in the past.

Does RF Training offer any help with new electricians once they are qualified?
We offer as much help via email or phone, or if necessary can visit on site for top-ups and refreshers.. Whatever is needed really. Tomorrow night I am meeting a former student of mine on the underground. He is doing very well indeed but is a little lacking in confidence with testing and more importantly, reporting. So I'm going to have a couple of evenings with him and his employees showing them the gaps in their knowledge and building up on their confidence to decide on observations.
Training centres should be able to offer some post course support of some kind.

 

[wade88]

Thanks Widdler, that was a very helpful reply.

Firstly, there are four warehouses here and from the schematics i have been looking over 8 distribution boards. Mainly three phase which i am not hugely familiar with. i work as an onsite electrician at festivals and events over the summer and install three phase systems on a temporary basis fed from generators around site but its a very different ball game altogether!

Yes, thats exactly the course i went on and obtained these qualifications:

City & Guilds (2382) – 17th Edition IEE Wiring Regulations (Level 3)

Logic Full Scope Electrical Part P Scheme

City & Guilds (2392) Certificate in Fundamental Inspection and Testing and Initial Verification

Logic Certification Domestic Periodic Inspection and Testing Award​

And as far as post help is concerned i believe all i have is the numbers of my tutors to ring if i need a "chat" or some advice. i have done this once....

The course was good, but of the 8 of us in the group we ALL had issues with many aspects of it and certain phrases became increasingly irritating such as "you dont need to know that lads" or "just do it that way its good practise" with no further explanation. i was under the impression that if i was to pay the money they were asking for which was a lot!..than i am entitled to an answer if i want it no matter how in depth it might have been. i was often palmed off with "thats more then u need to know ben, or, dont worry about that for now just concentrate on this" etc. which really began to get on my wick. I think if i dont get going pretty quickly and start immersing myself in electrical work then a refresher course id exactly what i need to do before long.

I apologise if i caused any offense with my remarks concerning NICEIC its just what i have been told at face value. i think its simply the cost that puts me off NIC as they are £100 more then anyone else. I have heard great things about Napit but dont feel im anywhere near ready to be taking my 2391, for at least 6 months to a year anyway but am very keen to aquire that qualification. seems to open a lot of doors.

ive been very impressed actually with the forum and the guys in it, and really didnt expect the level of help ive been getting. im very grateful to say the least i shall be sticking around for some time here i think!

If i had known my career in the police force was never going to happen and my degree would be worth no more than the paper its printed on to me, i would have gone for the apprentiship straight away when i finished college, and done this the proper way and got the experiance i needed as i went along over that period of time, but this was the only option available to me to obtain these qualifications, its just very difficult to try and apply a hugely limited knowledge to earning a living. we wernt even shown how to chase cable! so thats something im going to have to teach myself on someone else's wall... eeek. we didnt lift floor boards, we didnt lift carpet, we didnt really navigate cable etc etc, i think your getting the picture. i had my head stuck in the regs book for 3 weeks and did my part p for a week, then had exams, and wired in a few consumer units...despite being very practically capable anyway, my skills in this sector are grey to say the least!

Its daunting stuff, but i have to just attack it head on i suppose to keep it up and get that experiance.

 

[johnboy6083]

hi ben. First of all mate i dont think your qualifications (and experience) are suitable for anything other than small domestic properties, and even then you will struggle to get a grasp of averything. I cant see how you got the job, as i dont think i would get a job of that type if i applied, and ive got lots of experience in all types of electrical work, mainly industrial and commercial.
Please dont take this personally, because im not attacking your intelligence, or enthusiasm. All i ask is that at the end of the day, would you be happy putting your name to a cerificate saying that your installation is safe?

Good luck mate, but dont ever carry out a task you are not happy with.

John

 

[wade88]

Not at all John no offense taken here its all useful to me!

Well I use to be a manager a few years ago for the company and had worked for them on an off before then anyway. So i sort of just walked into the job when they heard i had become qualified i was offered a job straight away. im only working three days a week at the moment as im trying to allow the other four to get my electrical business on its feet.

i dont really want to just work in the domestic arena the plan was to get my photovoltaics qualification in good time and try and get into that, as i believe renewable energies are going to be most definitely the next big thing and i would like to get my foot in the door before the boom takes place. All the course was gearing us up to do was domestic work anyway so i wasnt expecting much else upon finishing it.

Well thats the thing John, I think i would yes, i have a good grasp of the regs and i dont do any work without it by my side and have conformed to it as best possible. but if i felt something was out of my depth then as you say, i simply wont do it. its just time, practise, time, practise for me now.