Megger 1720 R1 + R2 function

[birdman1979]

hi all , just got this new tester today ,quite impressed with the r1 r2 function using zref , doing PIR's at the moment and wondered what your thoughts were on using the r1 + r2 functions results on a cert , after verifying continuity of cpc and whether or not the zref can be stored ? cheers ps can i have a membership to the pub pls as i dont advertise im just a plain old subbie ATM

 

[Sintra]

Personally i think this R1+R2 calc being done by the meter is completly wrong. R1+R2 should NEVER be calculated.

 

[Deleted member 26818]

Yes well dodgey.

 

[vernam616]

agree with above, always measure the way i was taught

cowboys will be using this to acheive PIR's in 30 mins, potentially missing vital and dangerous points

 

[birdman1979]

thought so , will continue using traditional r1 + r2 method

 

[Deleted member 26818]

I'd consider using both methods, and comparing the results.

 

[telectrix]

it's a bit like driving into a tree at 50mph to see if the airbag works.

 

[GLENNSPARK]

Same here....R1 R2 should always be directly measured.........Also birdman, dont forget that r1 r2 rn is continuity of ring mate....R1 R2 is line&cpc...terminology is everything..........

 

[carball]

Thanks for the message.

 

[johnboy6083]

Remember that there is a reason why testing is done in order. Firstly you test the earthing and bonding. This is because it's the foundation of safety that the rest of the installation relies on. Then you IR cables. This is to ensure that your cables are sound. Then R1 +R2 is measured, along with R1+Rn and Rn+R2, for comparison. This also doubles up as circuit identification. Then it's onto live tests. Now if you just IR cables, and then straight onto Zs, then how do you know it's safe to energise that cable? Your CPC to that point may be corroded, and the safety of that circuit relying on parallel paths, that can be removed with no consideration of the electrical installation. A Zs will read ok, but an R1+R2 will pick this up, and confirm polarity!

 

[Deleted member 9648]

agree with above, always measure the way i was taught

cowboys will be using this to acheive PIR's in 30 mins, potentially missing vital and dangerous points

It is not always essential to measure R1R2 when carrying out a PIR. If a previous EIC or PIR is available to the inspector with R1R2 results,it is acceptable to measure Zs only,and if that is substantially the same as the Zs result on the previous cert it is reasonable to assume the R1R2 will also be the same. Obviously if this method is used it should be made clear on the cert,and if results dont match it would be necessary to carry out an R1R2 on that circuit to verify.