Zs - Ze = R1 + R2.. Is this right ??

[castlon11]

I agree thats the answer i was looking for..thanks..

I have another question for you, when doing a Ze reading at board, you are supposed to disconnect all associating c.p.c s to get a true reading. When you do your Zs readings do you continue to leave supplementary bonding unattacted ????
Also this theory about disconnecting the cp.cs has always puzzled me as although you want to test the true readings of the cables without interference from pipework ect, you are not testing the the installation as it is in normal conditions. If you understand what im going on about please inlighten me.

 

[Guest123]

Hi.

Ok when measuring Ze all you need to disconnect is the main earthing conductor from the earth bar/terminal and clip the croc clip on to it, leave all the cpc's where they are. Obviously for this the system will be de-energised i.e main switch off.

When measuring Zs however parts of the system will be energised so technically ALL bonding conductors and cpc's should be in place i.e under normal operating conditions.

 

[castlon11]

Ok so what i am saying is that when your testing Ze with just the main earth you are not testing the bonding conductors as well, however when testing Zs readings, all the bonding conductors are connected (in normal conditions), so the results dont relate to the Ze readings?????

To sum up:
1. Ze (with bonding conductors) + Zs (with bonding conductors) = Fair results

2. Ze (without bonding conductors) + Zs (with bonding conductors) = Unfair results - correct way of testing -

Number 1 seams to me the fair way of testing but not the correct way, explain why this is ?

 

[saveloy]

Ze is the external EFLI only so bonding conductors cannot be included in this test as they are part of the internal installation. Main Earth conductor is classed as part of the external EFLI path.

Zs is measured with the inclusion of bonding conductors as they will be present and provide an earth return path under fault conditions when the installtion is in service.

 

[castlon11]

Of course yes, so Ze test, bonding disconnected to prove actual main earth into the installation is present so bonding conductors cannot contaminate test results of main c.p.c. How stupid of me to not remember this,
Thanks.

 

[trebor]

When doing electrical tests i've always been told the way to get R1 + R2 is to minus your Ze reading from all your Zs readings, is this allowed ?or do all dead tests have to be done, considering the results are almost identical everytime whichever way you do it ????

Zs - Ze as a caculation of R1+R2 is perfectly aceptable on circuits that can not be de energised during a PIR, it should however be noted in the remarks column that it is calculated and not measured

Parallel earth paths are pretty irrelevant as Zsm is the recorded value regardless, so the parrallel earth path is effectively included in R2 much the same as using a conductor plus the armouring of an SWA

 

[confused-fuse]

have a read here
Ze; Zdb and Zs

 

[Des 56]

have a read here
Ze; Zdb and Zs

The link above seems to justify my reply to the question,quote
If you take the Zs and deduct the Ze you cant be sure that the R2 bit is the cpc or is some parralell paths giving you the same readings

The Zs could be taken this week and the R1+R2 calculated and next week a copper water pipe is changed to alcathene and bang goes your earth path

 

[ian.settle1]

have a read here
ze; zdb and zs

bs7671:1992?