Discuss Is there any way of getting the PEFC if you only have the Ze? in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

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I actually think it's good that they put in information that is irrelevant to the question. It means you have to read and think "What is it they're wanting here, what information is important and what is not" Just like you would in the real world.
 
measurement is better than calculation lol

Not always!
Consider the situation where supply transformer is close to the domestic installation intake and Ze is likely very low. The best BS EN 61557 EFLI testers are typically +-5% accurate +-3 least significant digits (lsd), so when Ze (or Zs) is less than say 0.1Ω the least significant digits become the increasingly significant error term as Z reduces.
Few, if any, EFLI testers actually measure the fault current, they in fact use the ‘measured impedance' as the divisor in a fault current calculation in which the measured voltage (or 230V nominal voltage, depending on the design of the tester) is the dividend and then it just displays the result in A or kA as appropriate. So it is easy to see that if the divisor is a very small number with a significant error, this can result in a very large current with a significant error.
To illustrate the point:
So if the actual Ze =0.05Ω,TN-C-S, then the PFC =230V/0.05Ω =4.6kA
However, our ELFI tester with a resolution of 0.01Ω, may be indicating a wildly different reading…
At increasing low ‘impedance’ values the +-5% tolerance becomes less important to the point where it becomes a second order term and we can effectively ignore it, however the +-3 lsd becomes increasingly dominant.
So, if the EFLI tester reads -3 lsd, Ze becomes approximately 0.05 – 0.03 Ω =0.02Ω, therefore PFC would read 230V/0.02Ω =11.5kA
So, if the EFLI tester reads +3 lsd, Ze becomes approximately 0.05 + 0.03 Ω =0.08Ω, therefore PFC would read 230V/0.08Ω =2.88kA
… do you still have blind faith in your beguiling digital EFFI tester, I hope not.
This is before we further complicate the issue with large CSA line conductors and their significant reactive components and the very low impedances we might expect in some commercial and most industrial installations, where the testing methods often have to be significantly different and more complex.
 
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Ashley, do you not believe what my learned friends are telling you? I am shocked that so many people have had to say the same thing....
 
do you not believe what my learned friends are telling you? I am shocked that so many people have had to say the same thing....

With all due respects, I have found the responses highly interesting, however, the one you posted, as per above does not do anything for me. In terms of interesting, take for instance the one copied below, from:

MarkieSparkie

"Not always!
Consider the situation where supply transformer is close to the domestic installation intake and Ze is likely very low. The best BS EN 61557 EFLI testers are typically +-5% accurate +-3 least significant digits (lsd), so when Ze (or Zs) is less than say 0.1Ω the least significant digits become the increasingly significant error term as Z reduces.
Few, if any, EFLI testers actually measure the fault current, they in fact use the ‘measured impedance' as the divisor in a fault current calculation in which the measured voltage (or 230V nominal voltage, depending on the design of the tester) is the dividend and then it just displays the result in A or kA as appropriate. So it is easy to see that if the divisor is a very small number with a significant error, this can result in a very large current with a significant error.
To illustrate the point:
So if the actual Ze =0.05Ω,TN-C-S, then the PFC =230V/0.05Ω =4.6kA
However, our ELFI tester with a resolution of 0.01Ω, may be indicating a wildly different reading…
At increasing low ‘impedance’ values the +-5% tolerance becomes less important to the point where it becomes a second order term and we can effectively ignore it, however the +-3 lsd becomes increasingly dominant.
So, if the EFLI tester reads -3 lsd, Ze becomes approximately 0.05 – 0.03 Ω =0.02Ω, therefore PFC would read 230V/0.02Ω =11.5kA
So, if the EFLI tester reads +3 lsd, Ze becomes approximately 0.05 + 0.03 Ω =0.08Ω, therefore PFC would read 230V/0.08Ω =2.88kA
… do you still have blind faith in your beguiling digital EFFI tester, I hope not.
This is before we further complicate the issue with large CSA line conductors and their significant reactive components and the very low impedances we might expect in some commercial and most industrial installations, where the testing methods often have to be significantly different and more complex".

 
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With all due respects, I have found the responses highly interesting, however, the one you posted, as per above does not do anything for me.


With all due respect to you, I wasn't intending to "do anything for you".
I just think that after all the excellent advice you have been given, a few "thanks" may have been in order to my learned friends rather than disagreement.
I hope that you have now got the hang of the difference between what a fuse can safely carry, and what it will "blow" at.
 
Ashley, AGAIN, with all due respect. Looking at previous threads you have created and posts proving that you are getting the basic things like Ze and Zs mixed up I don't think posts like MarkieSparkie's would do you any good.

You need to learn to walk before you can run. Master the understanding of the basics and then perhaps move on to more informative posts such as MarkieSparkie's:thumbsup

Good Luck :)
 
Suffice to say that Guitarist has 1 Friend mentioned in his Profile, & I do not have to go a million miles to see why 1shortcircuit came in straight away to criticise me after Guitarist. The concept of cyber bullying is not a new phenomenon.

This is a forum, the purpose of which is to promote critical thinking, meaningful problem solving & knowledge construction, take your cyber bullying elsewhere. I will decide what will do me good, it is not for anyone to make that decision for me.

I have found the responses from other members highly interesting & I found the one posted by Guitarist, did not do anything for me. That response correlated with some of the others that Guitarist has posted in other threads, in that they tend to have a low interest value, & tend to rant, the others did not. There was a world of difference between what MarkieSparkie wrote & the rant that came from Guitarist.
 
"This is a forum, the purpose of which is to promote critical thinking, meaningful problem solving & knowledge construction,"

2391 is not supposed to be a give away qualification, but it is not rocket science. Most of it revolves around Ohm's Law and knowing how and when to apply it.

I think you are getting confused with:

In, Icn and Ics.

Maybe a browse through Part 2 of BS7671 and the chapter on PFC in GN3 might clear things up.


 
Suffice to say that Guitarist has 1 Friend mentioned in his Profile, & I do not have to go a million miles to see why 1shortcircuit came in straight away to criticise me after Guitarist. The concept of cyber bullying is not a new phenomenon.

This is a forum, the purpose of which is to promote critical thinking, meaningful problem solving & knowledge construction, take your cyber bullying elsewhere. I will decide what will do me good, it is not for anyone to make that decision for me.

I have found the responses from other members highly interesting & I found the one posted by Guitarist, did not do anything for me. That response correlated with some of the others that Guitarist has posted in other threads, in that they tend to have a low interest value, & tend to rant, the others did not. There was a world of difference between what MarkieSparkie wrote & the rant that came from Guitarist.
Ashley, Guitarist is among the nicest, well mannered and clued up posters on here. If you think he's bullying you then you have very thin skin, wait till you annoy some of the guys here. Then you'll know mate
 
Suffice to say that Guitarist has 1 Friend mentioned in his Profile, & I do not have to go a million miles to see why 1shortcircuit came in straight away to criticise me after Guitarist. The concept of cyber bullying is not a new phenomenon.

This is a forum, the purpose of which is to promote critical thinking, meaningful problem solving & knowledge construction, take your cyber bullying elsewhere. I will decide what will do me good, it is not for anyone to make that decision for me.

I have found the responses from other members highly interesting & I found the one posted by Guitarist, did not do anything for me. That response correlated with some of the others that Guitarist has posted in other threads, in that they tend to have a low interest value, & tend to rant, the others did not. There was a world of difference between what MarkieSparkie wrote & the rant that came from Guitarist.

Youre coming across as a real jerk pal.
You started a thread and asked a question.
It was answered in the second post and everyone should have gone home happy.
You like to use long-winded lingo in otherwise empty tedious posts.
As internet trolls go youre small change so go jog on.
 
This.was in.the.2391 on.the 9th this.month.why warry should have reaulta.by the 12th.October if worse come worse.re sit.ir

Sent from my GT-I9000 using Tapatalk 2
 
This.was in.the.2391 on.the 9th this.month.why warry should have reaulta.by the 12th.October if worse come worse.re sit.ir

Sent from my GT-I9000 using Tapatalk 2
Grammer and spelling ? 'Full stop' to that too. Never seen such small sentences.
 
Suffice to say that Guitarist has 1 Friend mentioned in his Profile, & I do not have to go a million miles to see why 1shortcircuit came in straight away to criticise me after Guitarist. The concept of cyber bullying is not a new phenomenon.

This is a forum, the purpose of which is to promote critical thinking, meaningful problem solving & knowledge construction, take your cyber bullying elsewhere. I will decide what will do me good, it is not for anyone to make that decision for me.

I have found the responses from other members highly interesting & I found the one posted by Guitarist, did not do anything for me. That response correlated with some of the others that Guitarist has posted in other threads, in that they tend to have a low interest value, & tend to rant, the others did not. There was a world of difference between what MarkieSparkie wrote & the rant that came from Guitarist.

I think you have suffered another confusion here Ashley.

The use of emoticons and symbols such as :thumbsup or Good Luck should not be taken in a negative way. I have based my post on posts that you have made in not only this thread but I went to the effort of browsing previous posts in other threads to confirm my suspicion.

If you feel that my post is irrelevant and the post such as MarkieSparkie's is useful and you understand then that is superb, perhaps I judged you wrong? Perhaps I didn't? Who cares? I was actually trying to offer some critique and remind you that learning to walk before you run is a wise move. If you choose to disregard this that too is completely cool. I am most certainly not going to lose any sleep over it my friend.

I wish you luck with your understanding of the basics of the trade and sincerely wish you all the best on understanding the more difficult areas too. I hope you do well and pass your course:thumbsup

PS I am a big boy and do not need the assistance of/feel the need to attack/defend any member whether they be on my friends list in my profile or not.

F***ing Dime Bar!!!!

 
I have to say i have assessed over 1500 electricians in their competence in their ablilty to test and i would say i found some good some shocking and some average. Ofa all of then that are trained electricians it was obvious that so many became lazy in their thinking of the test it be came a chore and after much prompting answers were given which i wanted to hear. the regs and assoicated GN books have the relevent infomation that you need and yes it can be confusing sometimes depends on the teacher or the back ground of the learner actually learning. of what i have read (and i did type a error i missed a o.o oops smack on the wrist) i have not only seen the question answered in many examples but also the " why " this is information that has been given freely and what you do not think is relevent to the question of the 2391 exam actually is ! it the whole point of it. maybe you should ask why have you been given the questions in the first place or a copy of the exam they want you to pass!! but any one person can test i can teach my 6 year old the correct proceedure and method but he will not understand the "why" of what he has done . i would say anyone who has been as fortunate to have such a deeply explained answer given by experienced and competent persons wouldnt be so negative.
 
Suffice to say that Guitarist has 1 Friend mentioned in his Profile, & I do not have to go a million miles to see why 1shortcircuit came in straight away to criticise me after Guitarist. The concept of cyber bullying is not a new phenomenon.

This is a forum, the purpose of which is to promote critical thinking, meaningful problem solving & knowledge construction, take your cyber bullying elsewhere. I will decide what will do me good, it is not for anyone to make that decision for me.

I have found the responses from other members highly interesting & I found the one posted by Guitarist, did not do anything for me. That response correlated with some of the others that Guitarist has posted in other threads, in that they tend to have a low interest value, & tend to rant, the others did not. There was a world of difference between what MarkieSparkie wrote & the rant that came from Guitarist.

I'm really not sure how you can accuse me of being a "cyber-bully" when I merely ask that you show the members on this forum some gratitude, rather than keep arguing with them about basic knowledge. I very much resent that accusation.
It is people like you on this forum that make a lot of us think "why bother?"
As for "ranting"? Hmmm....
All of us on here give our knowledge freely and to help other electricians who genuinely need help (and occasionally DIY'ers too).
Anyway, I wish you all the best and hope that with enough help on the forum you will be able to learn some of the basics of our profession.
 
If you feel that my post is irrelevant and the post such as MarkieSparkie's is useful and you understand then that is superb, perhaps I judged you wrong?ng Dime Bar!!!!

The input that MarkieSparkie bought to this topic, I really enjoyed, & I am sure that you are as capable as him, in this respect, so please do not perceive my comments in this regard. If my perception, in terms of what I wrote after your post, is wrong, relating to the profile issue, then I apologise.
 
in terms of what I wrote after your post, is wrong, relating to the profile issue, then I apologise.

Absolutely no need to apologise in my opinion:). Everyone has an opinion and I am far from always being right.

One thing for sure, I won't be losing sleep over anything posted on a forum ;)

MarkieSparkie's posts are always VERY informative but often the content goes way over my head as I'm more of a small words/pictures man lol

:thumbsup
 
As always there will be differences of opinion.

I was always taught to use the Ze {measured} +(R1+R2) {again measured} and record the calculated results method.

The reason my mentor taught me this method, was if your calculated (two measured results added together) complied, then any parallel paths which lowered the Zs was a bonus, but not guaranteed.
You were actually measuring and calculating the worst case results, which were likely (but not guaranteed) to be better in reality, so if your results complied they could only get better, this he said was proper testing and proving compliance.
Likewise if you just measured your Zs, things could change later leaving you with a non compliant circuit.

On my own jobs I do the two measurements and calculate method and record this result, but still check the measured Zs just to double check that everything is ok.

I have worked on sites where they have wanted the actual measured Zs, but on the other hand I have been boll*cked on yet another site (same firm, different gaffer) where my Zs has been lower than the Ze (due to parallel paths), so it seems you cannot win, as always he who pays the piper calls the tune.
 

Reply to Is there any way of getting the PEFC if you only have the Ze? in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

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