Low insulation resistance on remote hager rcbo board and effect on upstream devices.

As the issue went away when the RCBO (functional) earth leads were disconnected, I guess you were testing L-PE or L&N-PE.

Assuming that 0.03MΩ is accurate - that's 30kOhms - whereas (in simple terms) you'd need it to be down to 7.66kΩ to get 30mA - so you'd need around 4x the number of boards/RCBOs to have any risk (although it would lower the "headroom" making unwanted tripping due to leakage from appliances more likely).

I am a little surprised at the numbers through - 0.03MΩ for 6 RCBOs would imply a resistance of around 180kΩ each (or 1.3mA each) - which feels a bit poor to me. I wonder if there's some capacitance involved that's not being fully charged by the IR meter and so fooling it into thinking it's a lower resistance than it would appear to be to 50Hz supply, or at that extreme end of the scale the IR meter isn't entirely accurate.

   - Andy.

Andy,

Thought it could trip at 12kohm (at 240v) since 20ma is over half the rcd rating.

                                                                                                          Hz

AJJewsbury said:

or at that extreme end of the scale the IR meter isn't entirely accurate.

I very much doubt that it is - the manual should give an indication. If "full scale deflection" is >999 MΩ, 30 kΩ is only 0.003%. The ohms setting may give a more reliable estimate, or even a good old-fashioned multimeter.

AJJewsbury said:

or at that extreme end of the scale the IR meter isn't entirely accurate.

I very much doubt that it is - the manual should give an indication. If "full scale deflection" is >999 MΩ, 30 kΩ is only 0.003%. The ohms setting may give a more reliable estimate, or even a good old-fashioned multimeter.