Ze - zs = r1 + r2?

[Simonslimline]

Do you disconnect all the parallel paths when measuring then??

Bad practice my arse.

How do you measure R1+R2 then?

 

[telectrix]

Do you disconnect all the parallel paths when measuring then??

Bad practice my arse.

of course it's bad practice. R1+R2 should be measured before the circuit is energised. otherwise, how do you ensure that it's safe to power up?

 

[YoungBart]

Just to stick my two penneth worth in... In my opinion it is bad practice to calculate R1+R2. This is a basic dead test that proves the installation is safe and correct.
However, I think It is perfectly acceptable (and maybe even safer) to calculate Zs (Zs= R1+R2 + Ze) as You will always get the worse case scenario and It saves removing any live accessory covers etc.
So IMO if you can be sure no one has 'tampered' with any of the install between Dead and live tests then I cant see a reason why You cant calculate Zs.

 

[LeeH]

of course it's bad practice. R1+R2 should be measured before the circuit is energised. otherwise, how do you ensure that it's safe to power up?

My bad, I quickly read this and thought it was a debate on calculating vs measuring Zs, not reverse engineering Zs by subtraction.

Apologise.

 

[jetandy]

Hello
I may be simple missing something here but if you put a link in at the board to measure your R1R2 and test at the last point. Surely you could still get a parallel path measurement. As the earth is connected to the met at the board. Or is that simple incorrect. As a z's is testing the earth loop and not just a low ohs resistance test?

 

[Risteard]

Hello
I may be simple missing something here but if you put a link in at the board to measure your R1R2 and test at the last point. Surely you could still get a parallel path measurement. As the earth is connected to the met at the board. Or is that simple incorrect. As a z's is testing the earth loop and not just a low ohs resistance test?

Indeed you could. We can both pretend that this is a very current thread.

 

[jetandy]

Indeed you could. We can both pretend that this is a very current thread.

Well it was just the most relevant one. So what if you can explain is the difference then between measuring the parallel path with a Z's as opposed to the R1+R2?

 

[jetandy]

Well it was just the most relevant one. So what if you can explain is the difference then between measuring the parallel path with a Z's as opposed to the R1+R2?

Are we suggesting that one should really remove the cpc and test the circuit individually. Otherwise I am still in the dark as to why the parallel path causes an issue for one test but not the other.