Recording Ze

[Piratepete]

Hi
I note that on the new 'Generic Scedule of Test Results' where there use to be a requirement to record 'Ze at origin' and 'PFC' (at origin), it is now 'Zs at DB' and 'Ipf at DB'.

Is there now no requirement to record Ze at Origin? I note that there is still a requirement to test Ze.

Pete

 

[Engineer54]

What ''Generic Scedule'' are you referring too?? There is always a requirment to test AND record Ze values!!

 

[sparkymalarky]

Actually lads there are two ways to obtaining Ze and Ipf values, by enquiry or measurement!

 

[i=p/u]

ze of board your working at which is zs of of the fuse before, ze zs all the same

 

[sparkymalarky]

No, Ze is the external earth fault loop impedance external to the installation. I know guidance note 3 refers to the Zs measured at a distribution board as Zdb but I choose not to.

 

[Engineer54]

ze of board your working at which is zs of of the fuse before, ze zs all the same

Oh Dear, Oh Dear, Oh Dear!! lol!!

 

[i=p/u]

and yes only 1 ze of installation but its when to apply ze zs or zdb, least i know what im on about lol

 

[Engineer54]

and yes only 1 ze of installation but its when to apply ze zs or zdb, least i know what im on about lol

Which is more than we do then ...lol!! Cause only Zs, Zdb applies after the main incoming supply point!!

 

[i=p/u]

in the book pointd out above it does use zs on test sheets as ze..

i know your worth double what i get payed e54, i know but can only say what i know:yes:

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or seen

 

[Engineer54]

in the book pointd out above it does use zs on test sheets as ze..

i know your worth double what i get payed e54, i know but can only say what i know:yes:

- - - Updated - - -

or seen

Then something is very wrong in that book!! Ze and Zs, are as i said earlier, ...Very different animals!! lol!!

 

[sparkymalarky]

What book is this? they are completely different!

 

[i=p/u]

test sheets should i say then... but struggling to find where now, maybe im yapping out my beeeeeep!

 

[sparkymalarky]

I found it! Page 93 of GN3 BS7671:2008 (without amendment). That sort ye out i=p/u lol

The schedule of test results in this version of GN3 does ask for Ze at origin. Stupid. New version is far better.

 

[Guitarist]

On the generic schedule of test results it does indeed say Zs at DB. This is exactly that... a generic term for the DB you are working on which may or may not be the one at the incomer. On the EIC itself however, you will find a space for the Ze.

 

[sparkymalarky]

I find this to be standard though, as all I work is EICR's on factories, large government offices, schools etc. I rarely will be completing an EICR with only one Distribution board. Sometimes its hard to get your point across on the old interwebatron.

 

[Piratepete]

On the EIC itself however, you will find a space for the Ze.

Where abouts? I've looked quite carefully!

 

[sparkymalarky]

Where abouts? I've looked quite carefully!

On Page 2, Section I - Nature of Supply Parameters...

 

[Piratepete]

What ''Generic Scedule'' are you referring too?? There is always a requirment to test AND record Ze values!!

Pages 98 and 99 of GN3 2012 edition and page 402 of Regs 2011 green edition

 

[sparkymalarky]

Piratepete, these pages that you have included from Pg98/99 of GN3 BS7671:2008 (2011) go along with the pages from 104&105 for an EICR(electrical installation condition report) and Pages 94&95 for an EIC (electrical installation certificate).

I think that is where you have been getting confused, hope this helps.

 

[wildgoose]

test sheets should i say then... but struggling to find where now, maybe im yapping out my beeeeeep!

Zs=Ze + [R1+R2).

So Zs and Ze can't be the same can they? I'm assuming you know what R1 and R2 is all about?

 

[Piratepete]

On Page 2, Section I - Nature of Supply Parameters...

Oh, b----r! I've always used this box to enter the worst case values - ie 16kA for Ipf and either 0.35, 0.8 or 200 ohms for Ze. The actual measured values I put on the Schedule of Test Results where the boxes used to ask for Ipf and Ze at Origin. Well, I've never been picked up on this in 10 years! Hurray for NICIEC assessments!

 

[ShaunM]

Hi to get the value of Zs the formula is as follows Ze+(R1+R2) R1 being the phase conductor and R2 being the CPC

 

[ShaunM]

Ze is the recorded external impedance at the intake of the supply, Zs is the earth fault loop impedance which is the total resitance of Ze PLUS R1 and R2

 

[sparkymalarky]

Welcome to the forum, but that has clearly already been established lol.