New to testing... Ze, PSCC & PEFC

[TPES]

I am new to testing and im trying to learn all i can about each test.

Today i have been practicing my Ze tests, PSCC & PEFC.

Please can someone tell me if i am performing the tests the correct way and if my results look genuine?
(I have a feeling my results on this occasion are way out)

I have added photos.
(If i press the "Display" button on my tester i will also get a current reading. So 2 photos to each test)

My Ze seems very high, Unless im doing the test wrong. Its a TN-S Supply and i understand 0.8 is the maximum.

I appreciate any pointers.

Ignore these photos, I know now there wrong, I got it right further down the post.

 

[Spudnik]

Hi Sid,

You need to disconnect the main earth from the bar and then test.

With it in place you are introducing parallel paths via main bonds and this will result in inaccurate results.

 

[Guest123]

Hi.

Pic 3 appears to be your Ze as the ohm symbol is displayed on the meter.

J, the earth is disconnected just hard to make out.

 

[Spudnik]

Fair enough.

Im gonna stay out of this one because the way the leads are connected dont make sense to me, especially with the first pics as i dont use a MM.

And the pics arent very clear on my screen as i cant even make out any symbols on the meter!

 

[TPES]

If i have the leads connected wrong please tell me.

My meter wont give any reading at all if i dont connect the way shown in photos.
It will display the voltage untill i press "start" then give my readings.

 

[Guest123]

Using my multimeter (megger) I test as follows-

3 wire lead

Ze, main earth disconnected red-line, black-neutral, green-earth.
PSC, main earth reconnected red-line, black-neutral green-earth.

 

[Mr Mark Sparks]

i might be missing something but those readings look like a tt job to me if they are tns then something is wrong

 

[Guest123]

Mark, Have a close look at pic 3, I think this is his Ze as the test leads are connected to obtain Ze and the reading on the meter is in ohms and is about right for a Ze. He has it labelled as PEFC but it cant be.

Whats your view on it.

 

[TPES]

i might be missing something but those readings look like a tt job to me if they are tns then something is wrong

Yeah it is TNS, I know these are very odd readings, Not sure why? What would be the cause of these high readings? Should i get intouch with the suppliers?

 

[Mr Mark Sparks]

lenny i have mft 1552 and cant see what scale hes on but agree leads connected for ze

 

[TPES]

On picture 3 my tester is set to "PSC L-N" this is what it says on meter for this setting, So i assumed this would be for my PSCC. Giving me the reading it does.

If I have tested wrong and Picture 3 is my Ze reading, Is it not above the maximum for a TNS, (being 0.8) ?

 

[kung]

Using my multimeter (megger) I test as follows-

3 wire lead

Ze, main earth disconnected red-line, black-neutral, green-earth.
PSC, main earth reconnected red-line, black-neutral green-earth.

Agreed ! didnt understand the reasoning behind ze with only cpc discon and crocked fine but n on line well and no line
Ze discon main cpc then crock using the 3 lead then n & l
pefc main cpc connected and crock cpc bar then l & n etc
pssc connect the earth probe to the n making it into a two wire tester and go between l-n.
Pfc is the highest reading taken from the two pfc readings between pefc & pssc.
Thought i was going mad

 

[TPES]

I think i can see what ive done wrong now.. What a plonker!

Still my readings are above the maximum for Ze??

 

[Guest123]

When I was in school 0.32 was lower than 0.80

 

[TPES]

When I was in school 0.32 was lower than 0.80

Ha ha ha, slap me!

 

[kung]

Dont worry its easily done at the start at least your doing it right not the pub diy bloke way !

 

[Guest123]

 

[TPES]

Because ive read in a number of places that Max Ze is..

TNCS = 0.35
TNS = 0.8
TT = 20

So because TNS is 0.8 as wrote and not 0.80,
This was why im thinking i have to get it lower than 0.8

 

[kung]

lol cool !

I am new to testing and im trying to learn all i can about each test.

Today i have been practicing my Ze tests, PSCC & PEFC.

Please can someone tell me if i am performing the tests the correct way and if my results look genuine?
(I have a feeling my results on this occasion are way out)

I have added photos.
(If i press the "Display" button on my tester i will also get a current reading. So 2 photos to each test)

My Ze seems very high, Unless im doing the test wrong. Its a TN-S Supply and i understand 0.8 is the maximum.

I appreciate any pointers.

tut tut and wheres your safe isolation ? (switch off and lock off) etc etc ?

 

[TPES]

Right, Heres my second go..

This is a TNCS, Better photos..

I know its a peice of cake to most of you but have i sussed it?

I lost my green crock clip, thats why using black one..

(And yes I do like creme eggs!!)

 

[Spudnik]

Right, Heres my second go..

This is a TNCS, Better photos..

.... have i sussed it?

Correctamondo!!

 

[Guest123]

Spot on mate.

 

[TPES]

Good Good!

So on EIC..

I put in the "External Earth Fault Loop Impedance Ze" = 0.20
& For my "Prospective Fault Current" from my readings what would you put in the "kA" Box ???

 

[Spudnik]

Good Good!

So on EIC..

I put in the "External Earth Fault Loop Impedance Ze" = 0.20
& For my "Prospective Fault Current" from my readings what would you put in the "kA" Box ???

Yep and the PFC box you put your highest value of PEFC or PSCC which is 1.01.

Odd though as normally on a TNCS they are near enough the same, but dont worry about that for now!

 

[TPES]

So from my readings you'd put in "1 kA"

and the maximum this can be is 16.5kA, Is this correct?... and this will be written in the "Short Circuit Capacity" Box on the EIC?

 

[Spudnik]

What certs are you using?

 

[TPES]

What certs are you using?

NIC EIC..

Domestic Electrical Installation Certificate

 

[Spudnik]

So from my readings you'd put in "1 kA"

and the maximum this can be is 16.5kA, Is this correct?... and this will be written in the "Short Circuit Capacity" Box on the EIC?

Ok Nature of Supply etc.

External EFLI Ze is the max so for TNCS its .35 There is then a box underneath for Measured Ze

PFC Single phase is what you measure so 1.01kA

Short Circuit Capacity is normaly 33kA for BS 1361 Type II 100A fuse.

 

[TPES]

Ok thanks J.. I dont know where ive got 16.5 from, ive seen it the max for something.

Where in the red book would i find these figures?

 

[Spudnik]

It is the max for some fuse types.


Have a look in the OSG Page 57

 

[TPES]

Type I, Thats where i got 16.5 kA from.

Thanks for your help lenny and J.. Appreciate it.

 

[Spudnik]

No prob mate.

Invoice is in the post.

 

[Guest123]

Cooking wi gas now son

 

[kung]

Hi Magic-sid
Do you have a lock off kit ? Remember switch off & lock off ! you will fail your assessment if you dont.
Regards
Kung.

 

[TPES]

Hi Magic-sid
Do you have a lock off kit ? Remember switch off & lock off ! you will fail your assessment if you dont.
Regards
Kung.

Cheers Kung... I do have a lock off kit yes, i know its not used on these photos..

Thanks

 

[kung]

Thought you were locking off with gorilla glue or no more nails lol
See not that hard onece you know mate ! best of luck with assessment !
Regards
Kung

 

[TPES]

Ha ha, thanks lads..

Ill be back soon with more simple questions..

 

[Spudnik]

We like them simple.

We dont have much brain power left at the end of the day.

 

[kung]

Yer me neither when i get in the kids and mrs are like that thing off dr who the Obsorbatoff or summit they drain all the sence out of me !

 

[Guest123]

We like them simple.

We dont have much brain power left at the end of the day.

Seconded.

 

[Gerry24]

Right, Heres my second go..

This is a TNCS, Better photos..

I know its a peice of cake to most of you but have i sussed it?

I lost my green crock clip, thats why using black one..

(And yes I do like creme eggs!!)

Jutke to say thanks for posting these pictures. I had my Elesca first assessment today which I passed. I had previously printed otf these picture and they were very useful to have on hand and for a quick reminder. Helped reduce the stress a bit.

 

[TPES]

Blast from the past!

No probs, i know what its like, i worried so much about every little detail on my assesnent, I owe alot of my thanks to this forum.

I used to think that sometimes i would learn more from going through these topics on the forum than i did at collage. Sounds daft but you get straight to the point answers and explanations on here.

 

[Thomas02]

Hi, I have only just come across this thread and it is extremely helpful to me. I am part way through my Level 2 at College and doing some testing during the practical sessions. Im ok with continuity and insulation resistance but a bit of live testing is being thrown into the mix by the tutor and I have been a bit confused by the order and procedure of the Ze/PEFC/PSCC tests. These pics and everyones comments are a big big help.

Thanks fellas!

 

[Bick]

Hi all, new to testing myself, but after looking through a testing book, i've noticed that there are 2 tests that can be done for PSCC. The first one is as the original poster demonstrated in the pics (really helpful BTW) of testing at the incoming supply between L + N. The second being performed at the neutral bar and after the MCB/fuse for individual circuits. I guess the point being that test 1 would be to test to check the main switchgear can handle the PSCC and likewise the MCB can also safely switch it's measured PSCC as well (the book shows 2 different amounts i.e main switch PSCC of 23kA and MCB of .82kA). I get the impression that checking the PSCC for individual circuits is often overlooked or rarely performed. Anyone got any thoughts about this?

 

[Jurasic Spark]

Right, Heres my second go..

This is a TNCS, Better photos..

I know its a peice of cake to most of you but have i sussed it?

I lost my green crock clip, thats why using black one..

(And yes I do like creme eggs!!)

First time I've seen this but i am the only one who thinks there is something wrong with pic 2 where the guy thinks he is measuring PEFC?

Also I think the 3rd lead is only required where there is an RCD upstream.

Any thoughts?

 

[Geoffsd]

Hi all, new to testing myself, but after looking through a testing book, i've noticed that there are 2 tests that can be done for PSCC. The first one is as the original poster demonstrated in the pics (really helpful BTW) of testing at the incoming supply between L + N. The second being performed at the neutral bar and after the MCB/fuse for individual circuits.

One method of testing. It can be done wherever you require on a circuit.

I guess the point being that test 1 would be to test to check the main switchgear can handle the PSCC and likewise the MCB can also safely switch it's measured PSCC as well

Yes.

(the book shows 2 different amounts i.e main switch PSCC of 23kA and MCB of .82kA).

23kA ???

I get the impression that checking the PSCC for individual circuits is often overlooked or rarely performed. Anyone got any thoughts about this?

Probably because it is not recorded anywhere.
Zs, and so PEFC, is done at many points and if this is satisfactory then PSCC, because it is usually higher, will be as well.



The readings on the meter in the pictures do not match up or make sense.

 

[Bick]

One method of testing. It can be done wherever you require on a circuit.


Yes.


23kA ???


Probably because it is not recorded anywhere.
Zs, and so PEFC, is done at many points and if this is satisfactory then PSCC, because it is usually higher, will be as well.



The readings on the meter in the pictures do not match up or make sense.

Thanks for the reply Geoff. The values i've given are not calculated or anything, they are just given as 2 separate examples with what seem an emphasis on the individual circuits producing a smaller PSCC due to the fact that the smaller conductor size would be higher resistance. The point i was trying to make being that the main switch being able to handle a higher PSCC than the MCB therefore in a fault condition the mainswitch may be able to safely switch the fault but the MCB may not leaving it in a potentialy damaged state after a fault. Seeing as a Live/neutral fault on an individual circuit could potentially produce a higher fault current than a PEFC (CPC being a higher resitance IF smaller than main conductor). Add into the mix RCD's, that only protect earth faults and there is what seems to me a weak link in the chain (at least one that's being overlooked) maybe this is why the book is showing the 2 tests?? All highly speculative and worse case scenario and not sure my chain of thought is correct but i think you can sort of see my logic??

 

[Geoffsd]

Yes, but just to clarify, if I have understood, the main switch does not disconnect on a fault.

So Zs is to determine that the MCB will operate and Ze, the supply fuse.

I'm not sure what you mean by an RCD being a 'weak link' as they are rated for the same fault current as MCBs.

 

[TPES]

First time I've seen this but i am the only one who thinks there is something wrong with pic 2 where the guy thinks he is measuring PEFC?

Also I think the 3rd lead is only required where there is an RCD upstream.

Any thoughts?

What an old post!!!

So... What is your method of testing PEFC? How do you carry this test out? It maybe confusing for some people who only have 2 lead testers