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Hi all. Newbie please be gentle...

My daughter in law moved into a new [2007] build. All socket circuits 20A radial MCB. One socket circuit trips rcd intermittently when the Wi-Fi router psu plugged in. Psu is double insulated and pat tests ok. Radial tests out ok with 50M ohm at 500v. Nothing obvious in the socket backs. Any ideas what to look at next? I'm here for the day visiting. Thanks!
 

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is it the RCD that rips or the MCB that's switched off in the pic?
 
meant trips. 5 blllody words/
 
you could try moving the suspect circuit over to the other side and fit a RCBO.
assuming the 45A is shower, this could do with moving to the RCD side. winner both ways.
 
45A is cooker. It's a rental property that they have just moved into and I'm here on holiday so a bit loath to start rewiring it! Was just after things to look for fault finding. Does 24ma seem low for the trip current?
 
Just curious. It looks like a pre-made connector, designed to slip into the cavity wall behind the back-box, but it must be at the end of the circuit, so not much use anywhere else unless you can connect the next socket somehow, Either way, it looks like you need two sets of connections for the socket...rather than just connecting the cable direct to the socket outlet?
 
Yeah weird wiring. All circuits are radial 20A. No RM here. But each socket has one wire going in only. So there must be a JB in the cavity somewhere.

Anyway whacked a new RCD in, see what occurs.... thanks for all the replies.
 
As above, if this is a rental property then under no circumstances should you be interfering with the electrical installation without the landlord's consent.

The landlord/landlady should be contacted to organise his/her own Electrician.
 
If each socket has just one cable, per the photo, and each one has these "connectors" then clearly there must be a JB, or perhaps several, somewhere. So instead of a supply cable looping in and out we have a JB supplying several sockets, each of which has one of these connectors? So we have 3 terminations per socket? Thus we have extra points of connection that can go wrong? Each socket will be traced back to the JB for fault finding? I do see the logic in this system, and can see an advantage or two, but in reality it seems like a bit of a faff. If those plug-in chaps can't take another cable, you would have to extend the circuit by using the terminals on the socket outlet itself, per usual...and if you feed say 10 sockets from a JB or some other connection outlet, you have a kind of spiders web effect, rather than a true radial?
Just asking...keen to learn.
 
On a different subject I have to say the insulation on the phase conductors where they terminate into the OCPD s are damaged lol, a steptoe and son job
 
Yup, agree with the above.
Prob best not to alter anything if it doesn't look standard.. just have a moan to the landlord and get them to sort it.
Could be a can of worms
 
Psu is double insulated and pat tests ok.

Did you test it yourself, i.e is the test trustworthy? I mention this because if it was someone else's test, I would double check it. A lot of numpty testers don't seem to connect the earth probe to the DC output connector when they 'test' small power supplies, so in fact they are not testing anything. It could have any amount of leakage or insulation failure from line to output but they wouldn't find it.

Actually, what happens if you power-up the PSU but don't connect the DC output to the actual router? Keep the plug out of contact with anything, so that there cannot be any earth leakage because the only connections are to L & N. If the RCD now doesn't trip, that suggests it is a leakage problem. If it trips, then you have something spooky going on.
 
Had a similar problem on a job myself recently and it may just be a coincidence that the RCD trips when the router is plugged in as the neutrals are common.
24mA is not too low for a 30mA RCD. You don't mention the 'half times' test, may indicate a faulty RCD.
Also no IR test results - Possible cable fault!
If the circuit tests satisfactorily, its possible the accumulated leakage current from all the RCD protected circuits exceeds 24mA.
 
So you whacked in a new rcd...which means you are now responsible for that circuit....or all the circuits on the rcd side....hope you have filled out an EIC or if anything goes wrong in that property you will be liable...not the landlord
 

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