rcd tripping

[PaulW]

Working on a tt installation with resistance reading in excess of 200 ohms.
MCBs are single pole, neutrals on common bar. Newly installed 'cheap' rcd is double pole.
Rcd is tripping, but not consistantly. Have isolated possible circuit fault is on, but cannot find any obvious reason for tripping.
Possible N-E fault from another circuit?

 

[Octopus]

Working on a tt installation with resistance reading in excess of 200 ohms.
MCBs are single pole, neutrals on common bar. Newly installed 'cheap' rcd is double pole.
Rcd is tripping, but not consistantly. Have isolated possible circuit fault is on, but cannot find any obvious reason for tripping.
Possible N-E fault from another circuit?

Who knows, not enough to go on. What tests have you done? Who installed the "cheap" RCD? the questions are almost endless

 

[Marvo]

When you say a TT with a resistance >200ohms, how much greater and are you testing the Ra value or are you including parallel paths? When you tried to localise the fault did you use a mega tester? What IR readings did you get?