R1+R2 Calculations from ZS

[malcolmsanford]

Oh dear the electricians perennial debate rears it's ugly head again, which is the more accurate Ze + (R1+R2) or Zs measured direct, this could be a long thread rivalling exported earths.

And not a parallel path in sight ................................yet .....................as you say Markie could be a long'un this

 

[ezzzekiel]

i cant figure out why all the variants have come from on installation certs, why couldnt they all simply reproduce the ones from the regs without deciding they need to add more info to them.

personal hate is the ammount of points box.

 

[keefy]

Simple, Zs. Its the 'active' reading taken when the cores are in normal working conditions, at the highest temperature and highest resistance and the reading is the most onerous. Whereas R1 + R2 ensures you have sufficiently low resistance to safely energise the supply.

If you are checking your cables are intact then that is R1 + R2, if you are checking to see if your work will not kill some poor unsuspecting member of the public then that's your Zs.

Sorry I misread the post, R1 + R2 is more ACCURATE, but Zs is more important. Yes the reading of Zs depends on whether the circuit is under load, but normally there is some sort of load, especially on lighting circuits... I love switching them all on for the first time!

 

[nickblake]

An experianced tester when carrying out an R1R2 test will have a rough idea of what results to expect , some times when you do a test you can get a high R1R2 and when you carry out a Zs test you get a lower Zs reading than you should get ,this could be due to parrallel earth paths, so realistically you should do a dead R1R2 test at more than one point ,because if your last point is on the bathroom lighting circuit and it has a supplimentary bonding conductor from the light to a shower as it should be to 16th ed then the reading you could get would be incorrect due to the paralle earth path , how ever this should be disconnected prior to the Zs any way , im a firm beliver in doing it properly R1R2 ,IR,Zs,RCD,Ramp , than you know your readings are correct

 

[malcolmsanford]

According to the NICEIC Nick we can't do live Zs testing as it is dangerous and classed as live working ..............your a very very naughty boy.

 

[telectrix]

and into the equation comes the internal resistance of MCB and RCD........affecting the value ofZs.

 

[nickblake]

Glad im not with the NIC then , they should get a life , so how do they do a dead Ze test , and its good to be a naughty boy ,lol , gee ill have to wear my wellies to do it then , think they need to get out of there offices and come into the real world

 

[nickblake]

and into the equation comes the internal resistance of MCB and RCD........affecting the value ofZs.

Blimy telex you had your sugar puffs this morning then

 

[keefy]

According to the NICEIC Nick we can't do live Zs testing as it is dangerous and classed as live working ..............your a very very naughty boy.

Yea! Do a dead one instead!!!

 

[malcolmsanford]

Yea! Do a dead one instead!!!

hmmmmmmmmmm Zs = Ze+ (R1 + R2) was always a dead one, well dead by calculation I should add

 

[telectrix]

Blimy telex you had your sugar puffs this morning then

just had me brekky. coffee and a smoke. nailed that earth fault. Ze=0.16 TNC-S, Zs 347. RCD internal resistance 347. sheesh. bloody MEM rubbish.

 

[RogertheBodger]

Well done Tel, one for your memoirs?

 

[Sintra]

just had me brekky. coffee and a smoke. nailed that earth fault. Ze=0.16 TNC-S, Zs 347. RCD internal resistance 347. sheesh. bloody MEM rubbish.

Happy days mate you will know to look out for that again.

This is why a Zs test must be carried out after R1 + R2 as it is the only test that actually goes full circuit. (not aimed at you Tel but for general info)


Sent from my iPhone using Tapatalk.

 

[Guest123]

Has anyone read the article in Marches Proffessional Electrical magazine regarding 'live working' taken from the HSE document.

Seems we can after all...........

 

[malcolmsanford]

Has anyone read the article in Marches Proffessional Electrical magazine regarding 'live working' taken from the HSE document.

Seems we can after all...........

Lenny I can't get that out here, any link perchance mate