RCD tripping

[Nick bromage]

Hi all .new to the community here and hoping for some thoughts

Situation is that had a plasterer to do a wall in the kitchen .

He tried to plaster around the socket (which is a switch to a fan ) the switch is a spur of kitchen ring which is under a RCD.

When he moved the switch (which was live still .( Don't ask!) Shorted the circuit and tripped RCD. Could have been moisture or touching wire not sure

Everything was working before and is modern cable
No other cabling was anywhere near the plaster area

Anyway

Each time I turn MCB on RCD trips
I have . Isolated all sockets in the "damp" area . No joy
Checked continuity at the CU.
All still as it was previously.

Isolated the whole of the kitchen sockets (even though continuity was ok)

Still trips . No load anywhere

Question . Could the plasterer have caused the MCB to fail?

Have bought new MCB but just want to ask around as I don't believe too often in coincidence

Thanks

Nick

 

[AndyPRK]

probably still a brown or red wire touching metal somewhere

 

[Nick bromage]

The relevant sockets are all isolated now. So bypassing the area
Just changed the MCB .
No joy

 

[EFLImpudence]

I'm confused.

You say "The RCD tripped" and also "Each time I turn MCB on RCD trips".
If the RCD tripped, why is the MCB off?
Some RCDs require all the MCBs to be turned off to reset them. Is that what you mean?

What does "all the sockets are isolated" mean? You did call the switch a socket.

 

[Nick bromage]

Hi Andy

I have isolated the offending swicth .

And just changed the mcb.


Turn on the mcb and RCD trips.

 

[Nick bromage]

EFL .
The mcb was subsequently turned off to isolate the kitchen area.

I have disconnected the wire from the spur that supplies the fan so it is no longer connected in anyways

The mcb is off now because if I turn it on the RCD trips which cuts off all power to other MCBs

 

[EFLImpudence]

I have isolated the offending swicth .

What does that mean? How? Have you disconnected the cable from the ring?

And just changed the mcb.

It was the RCD that tripped, wasn't it?

Turn on the mcb and RCD trips.

RCDs trip because of current leakage to Earth.
From Line(live) conductors or Neutral conductors.
This can be caused by damp or a wiring fault.

 

[EFLImpudence]

The mcb was subsequently turned off to isolate the kitchen area.
I have disconnected the wire from the spur that supplies the fan so it is no longer connected in anyways
The mcb is off now because if I turn it on the RCD trips which cuts off all power to other MCBs

Just saw your post.

Ok. so it's not the switch that was moved by the plasterer.

I would suspect moisture somewhere or other damage then.
It seems an unlikely coincidence.

Unless you can see something apparent or can test the circuit, then you will need an electrician.

 

[Nick bromage]

Yes the cable is fully disconnected.
And yes it's the RCD that trips when I turn on the MCB
The ring main wiring was fine before the incident

The ring is above the ceiling which only had a 3mm skim on it

 

[Nick bromage]

I am retired electrician
That is one reason I am somewhat confused.
Haven't been near any of the ring circuit where it is damp in fact the ceiling had been finished ( where ring runs Above it ) and plasterer was working on a small wall area hence the switch.
Convinced it's relevant to the incident with the tripping but none of that is now connected as I have disconnected it.

How much damp can cause a problem?

 

[EFLImpudence]

How much damp can cause a problem?

Well, not much in the right place. Wet dust etc.

As the RCD can be reset with the ring MCB OFF, it would suggest that it is the Line(live) conductor which is the cause - if no heavy loads connected.

Can only suggest that you disconnect half the ring to determine where the fault is, then half of that faulty half, etc. and hope you can see something.

 

[Nick bromage]

Cheers . Going to temporarily run 2 new cables from CU to where I have access to the ring (thus by passing the possible problem area )
At least it removes one more variable