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Hi everyone,

I have a problem in a home. By night time his rcd is tripping for no reason. I made and insulation test between neutral and earth + live and earth and got 4 mega ohms. I made a leakage current test and found he have 20mA. Can somone tell me how i can minimize it please since i made a current test on the rcd and found out it is tripping around 22mA.

Thanks
 
If your global insulation value is 4 million ohms then the fault leakage current wouldn't even by 1 miliamp. That means you've got functional leakage probably peaking in the region of 22mA or more.

Global functional leakage isn't a fault so you can't 'fix' it as such, you can only manage it. You could leakage clamp test all the final circuits individually around the L+N conductors as a live test to determine if there may be an appliance or item with higher than usual functional leakage. If nothing stands out you can only manage the effects by spreading the loads across more than one residual current device...ie fit individual RCBO's on the final circuits rather than a single RCD as it is now.
 
Was your IR test done over the whole installation?
Need to break it down to individual circuits.
Why is there high earth leakage?
Is it due to Appliances or fixed wiring?
 
Does it only trip overnight? A plug-in mechanical motorised timer can help determine the time it happens which might aid fault finding.

Does the installation have a large number of IT or video equipments?

Has there been a water leak or flooding?

Check the immersion and kettle elements.

Is there an underground cable to any outbuildings - check it.

Check old fridges and freezers.

Any nails or screws been put in the walls recently?

Just some thoughts...

Please keep us posted - we armchair detectives love that.
 
Last edited:
Hi - from the comfort of my couch I agree with my esteemed colleagues above :) .
I think at 4 meg Ohm you might be reading surge protector impedance. Lots of appliances have them, including plug boards. Unplug everything, turn off the cooker and boiler isolation switches and retry at 250V. And so my bet is the leakage will be from appliances :) .
 
I'll have a wild stab in the dark too then.

1, high background leakage, many 'leaky appliances and/USB sockets etc.

Coupled with,

2, failing immersion that is coming on on a timer at night adding the straw that breaks the RCDs back.

Or

3, something else entirely.
 
unplug appliances you don't need overnight ....... that said I would be looking more closely at your fridge and freezer .

Have you tested the RCD properly?
 
As you all know I'm the old git still training/learning but a few years back a friend had rcd tripping in night randomly.
Even with every thing unplugged and isolated still did it.
Tested and couldn't find anything , after checking in back of socket outlets eventually found some of the cable were squashed tight against back box due to excessive length of can less so dropped socket fronts of for a night and didn't trip so shortened and sleeved the ones that had squashed insulation and job sorted
 
Thank ypu everyone for your help. I appreciate it. I managed to splve the problem by changing the rcd brands from aeg to schneider since i found out aeg are tripping around 22 ma and the other at 25ma.
 

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