Rcd tripping

Trapeze

I had a rcd tripping and isolated it to kitchen. I unplugged everything but still tripped. I started opening the sockets and on third one I found the cause. It was a recently dead mouse.

Is there a way that I could have found which socket it was by using a multimeter?

I think that the reduced resistance between earth to L or N would have carried over to all the kitchen sockets? What do you think?

meercat

its Unlikely you’d have found that with a multimeter.

I’m going to play devils advocate here and wonder if that’s the cause

id regularly remove sockets and find dead rodents inside (not causing the rcd to trip)

Trapeze

Thanks for replying. I'd had a few intermittent trips over the past 2 weeks, but was permanent today (thankfully as I could go hunting for problem). Fingers crossed 🤞.

10-10-20

The reason why multimeters won't often pick up these defects is down to the test voltage and high resistances. Multimeters use low voltage DC (1.5 to 3v) while an electricians tester in IR (insulation resistance) mode would use 250 V, 500 V, and 1000 V. At these higher voltages you can detect degraded or damaged insulation which won't be apparent at low voltages. Also they test for resistance in the 1000 M-ohm range, far higher than most common multimeters.

corsav6

Ethos and Fluke both have a plug in tester. It will test for earth faults, continuity and crossed wires as well as more. Probably no harm to have 1 around the place for future.

Antenna

https://www.boards.ie/discussion/comment/119720374#Comment_119720374

Lidl (or it could have been Aldi?) had a plug in tester recently. Regarding crossed wires, one scenario it can not detect is N and E being crossed. However plugging in and turning on almost any appliance will cause the circuit's RCD to immediately trip if N and E are crossed.

Trapeze

https://www.boards.ie/discussion/comment/119720363#Comment_119720363

But in my instance -with all the sockets in the kitchen looped from one to the other- would the fault on the problem one cause the same resistance to appear on all the looped sockets on that circuit? , regardless of the type of testing device used.

Trapeze

https://www.boards.ie/discussion/comment/119720374#Comment_119720374

Do these work with a socket with no power?

kirk.

https://www.boards.ie/discussion/comment/119721065#Comment_119721065

Ya had me wondering there for a second but ya the N-E reversal doesn't display on testers but any load will trip rcd.

Off the top of my head a fault loop impedance test will read as normal for N-E reversal and a RCD trip test won't trip the RCD, could be wrong there.

10-10-20

https://www.boards.ie/discussion/comment/119723100#Comment_119723100

Pretty much yes, as the fault was probably a mid-to-high resistance L to E through a decaying mouse.

If the fault had been a low resistance short then you could have measured the resistance from each socket and noticed that it increased the further away you got. Then if it was a ring you would have split it at a mid-point socket and repeated the test to uncover which side the fault was on. You could then use the resistance of the fault to calculate the distance to the short and work from there.