Megger 1721 2 wire test

[flyingsparks]

i have a new megger 1721 (always had fluke before). Today I did a 3 wire low current loop test and got 0.30. Then tried 2 wire low test and got a reading of about 2.30. Why’s it so different.?
Thank you!

 

[chivers67]

Did you do a two high? Or were you worried about tripping an RCD due to "critical" circuit testing. What circuit was it?

 

[JohnW2]

Did you do a two high? Or were you worried about tripping an RCD due to "critical" circuit testing. What circuit was it?

I think one of the potential problems, at least theoretically, is that undertaking a loop impedance test which results in an RCD tripping can (depending upon factors such as how quickly the RCD operates) result in incorrect loop impedance results - so I would think that it is probably generally desirable to avoid an RCD trip, even when the circuit is 'non critical'.

Kind Regards, John

 

[Iggifer]

Hi current testing is MUCH more accurate on my 1552. I dislike the three wire no-trip test. It's super slow and the slightest bit of noise on the circuit makes the reading a joke (luckily they're so wrong it's obvious)

That being said, it's always higher on no-trip by anywhere from 0.20Ω to 0.50Ω. Never as much as 2Ω though.

I'd recheck that reading and if it's the same I'd be on the phone to Megger. I'd class that as faulty. Hardly usable is it?