Rcd tripping when mcb switched on

[Darren713]

Hi I recently got water in one of my kitchen sockets which resulted in, I believe, my rcd tripping. My mcb didn't trip.

I switched each mcb one at a time to find yes it is my kitchen circuit. Due to this I replaced the socket in question with a dry one and checked all wiring was dry, however when I switch on the mcb it trips the rcd still.

Would appreciate any advice as this is beyond my basic knowledge or does the mcb need replacing?

Thanks

 

[RF Lighting]

This indicates a short from live to earth. Unscrew the socket you replaced and make sure you haven't trapped any wires or pierced them with the faceplate fixing screws. Take a photo and post it on here if you're not sure what you're looking for.

 

[canduit]

This indicates a short from live to earth.

Or neutral to earth?

Edit: oops, yes, live could mean line or neutral!

 

[JohnW2]

This indicates a short from live to earth.

Or neutral to earth? Edit: oops, yes, live could mean line or neutral!

No, it really has to be line-to-earth if the RCD tripping can be avoided by switching the (single-pole) MCB off. Switching off the SP MCB cannot clear a N-E fault.

Kind Regards, John

 

[canduit]

Yes, correct, I should read the OP properly next time

 

[Taylortwocities]

Yes, correct, I should read the OP properly next time

I sympathise.

 

[EFLImpudence]

I don't. I cannot stand people who don't read posts properly.

There's obviously something wrong with the fan.

 

[bernardgreen]

Due to this I replaced the socket in question with a dry one and checked all wiring was dry, however when I switch on the mcb it trips the rcd still.

Is there anything plugged into a socket on the circuit that is fed by that MCB when the MCB is switched ON ?

Could the water have affected any other circuit such as lighting or cooker supply ?


If there is any load ( fridge, kettle etc. ) on that circuit when the MCB is switched on then a N-E fault due to water / dampness on another circuit could be the reason the RCD trips. This trip happens even if the MCB for the circuit with the N-E fault is turned OFF.

Neutral_Earth_trip

• bernardgreen
• 16 Jan 2011
• 48

 

[JohnW2]

If there is any load ( fridge, kettle etc. ) on that circuit when the MCB is switched on then a N-E fault due to water / dampness on another circuit could be the reason the RCD trips. This trip happens even if the MCB for the circuit with the N-E fault is turned OFF.

True - but that would be equally true if the MCB of any circuit (on the same RCD) which had any load was switched on, but we've been told that it is only one MCB which does it (although I suppose it's just possible that all the other circuits are unloaded).

An L-E fault on the kitchen circuit is obviously the simplest and most likely explanation.

Kind Regards, John

 

[bernardgreen]

An L-E fault on the kitchen circuit is obviously the simplest and most likely explanation.

I agree but if the affected socket is now dry and the trip still occurs then a bit of lateral thinking may be needed.

 

[JohnW2]

An L-E fault on the kitchen circuit is obviously the simplest and most likely explanation.

I agree but if the affected socket is now dry and the trip still occurs then a bit of lateral thinking may be needed.

Yes, it may be needed. However, if the OP can confirm that there's nothing amiss with the replaced socket (trapped wires etc.), my money would initially be on some water having got into something else, causing an L-E leak. I would think that an N-E leak great enough to trip an RCD would be very unlikely as a result of water (if water is the culprit).

Kind Regards, John

 

[deadshort]

We have not been told how much water and the direction of flow ? so, it's possible the room has been flooded and a JB or a damaged cable has be soaked.

Really needs a IR test and an electrician


Regards,

DS

 

[JohnW2]

We have not been told how much water and the direction of flow ? so, it's possible the room has been flooded and a JB or a damaged cable has be soaked.

Yep. As I said ... "...my money would initially be on some water having got into something else, causing an L-E leak".

Really needs a IR test and an electrician

Again, yep, it probably does. I don't think that I'd get much of a prize for predicting what the initial whole-circuit IR test would show, but the fault(s) (maybe lots of JBs full of water!) clearly need to be localised by more detailed testing.

Kind Regards, John