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anyone else got one? Ever used the R1+R2 setting?
Was testing a socket circuit for a minor works yesterday fed from a 36 way TP&N DB Everything except the fire alarm was wired in singles through trunking absolutely none of the earths were remotely near the terminals that they should have been in like circuits down the left side had cpcs on the right side earth bar and in no particular order. Also vice Versa and some left side cpcs in the left side but again in no particular order :rolleyes: The nuetrals were all in the right place but it looks (the ones I checked anyway) so it ended up taking me about an hour to find the earth for the circuit I was working on which was at the top of the left hand side so really should be in the top of the LHS earth bar nope was in the middle and the bottom of the RHS earth bar (it was a ring)Anyway found it done R1+R2 all good and superb readings so definitely found the right cpcs.
It got me wondering if in a case like this I’d have been better off using the R1+R2 setting on the megger like turn it to Zref get a Ze from the phase that the circuits fed from and then turn it to the R1+R2 setting and batter out the tests that way I was curious as to how accurate it was and every single reading I took was within 0.02 ohms of the actual R1+R2 readings some were actually dead on just wondering if it would actually be acceptable to use this setting or if it would be frowned upon? Obviously if the cables and CPCs are all in the right place I’d do it the right way cause it’s easy enough when you don’t have to go searching (and I know I could have just done an R2 but I wanted the R1+R2) what’s your thoughts on using the R1+R2 setting in circumstances like this?
 
Is it a dead test or a live test? I'm not familiar with the Megger MFT's, haven't used one since the 1552 about a decade ago.
afaik, with the 1720, you can measure the Zs and then it can give you a calculated value for R1+R2.
 
So for the circuit worked on I short the L to the earth bus and measure at the far end of the circuit the calculate the expected ohms as a check and you can measure the L alone and the earth is usually the same mm² so you double it basically. Or if it is smaller (E) you can calculate accordingly. Often come across the mixed up ends of circuits with not the slightest pretense of following numbers on the bus bars.
 
The MFT 1730 has this R1+R2 feature, but I've used it only once about four years ago to see how it worked and haven't used it since. For all the time it takes to carry-out an R1+R2 test, I prefer the conventional method.
 
Pretty sure I seen advertiser in PE recently that Flyke have made a tester that will carry out IR, R1+R2, Zs and RCD/RCBO all in one test.

Interesting. That would certainly speed things up on an EICR!
 
From what I read into it: Trips the RCD then does IR when dead. Will only work on RCD circuits.

Dillb. For continuity you could just calculate it from the Zs at the DB

Would be handy in EICRs but maybe not for big commercial ones where not everying is RCD protected.
 

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