Intermittent Tripping Rcd fault

[Welsh_sparky_21]

Feel like I’m posting on here every week for advice is a reading of 0.18 megaohms between neutral and earth enough to trip and RCD. Sent to an intermittent Rcd tripping, everything else seems clear bar this one cable. As always nothing tripping while I was there. Ramp tested the RCD and 15ma was the result. Seems very low to me

 

[Markyd]

0.18 Mo doing what an IR test

 

[Lucien Nunes]

is a reading of 0.18 megaohms between neutral and earth enough to trip and RCD

No, would need to be around 500 times lower to be a real problem. Use ohms law. Say there's 5V drop in the neutral conductor total, i.e. 5V across the N-E insulation. To get 15mA leakage would take 5/0.015 = 330 ohms or lower.

But as I was posting elsewhere yesterday, an abnormal low IR that doesn't itself cause a trip can nonetheless act as a beacon to show where a cable is damaged that might cause intermittent tripping for some other reason.

 

[timhoward]

15ma ramp test is about the lowest it can be for the RCD to be considered within spec. Was that with all loads on or with loads isolated?
Finding intermittent trips on an Rcd board can be a right pain. Anything with a thermostat or a timer is a suspect, eg fridge/freezer self defrost, immersion heater.
Kettle, cooker ring/oven element.
Occasionally a smart meter.
Best of luck!

 

[Welsh_sparky_21]

15ma ramp test is about the lowest it can be for the RCD to be considered within spec. Was that with all loads on or with loads isolated?
Finding intermittent trips on an Rcd board can be a right pain. Anything with a thermostat or a timer is a suspect, eg fridge/freezer self defrost, immersion heater.
Kettle, cooker ring/oven element.
Occasionally a smart meter.
Best of luck!

Loads were connected at the time, yeah its a needle in a hay stack at times

 

[Lucien Nunes]

If loads were connected you shouldn't really be testing L and N separately to E, only in parallel. Otherwise the test voltage appears across the load and can cause damage in theory (although usually OK). 0.18 meg is typical of surge-protected leads and adaptors. Did you try a test at 250V?