RCD keeps turning off but nothing else

[NullCipher]

Apologies for the lack of terminology, or incorrect here.

On our CU, we've got half behind an RCD. For some reason this morning, the RCD turned off whilst all of the RCBO's remained on

I turned the RCD back on, and 5 minutes later it shut off, same scenario. Tried again, shut off immediately. Left it for 20 minutes, tried again and its fine.

Is this how an RCD behaves? I was under the impression that it should be the RCBO that would trip rather than the RCD on its own?
Any suggestions?

 

[Blueflash]

The RCD has detected a fault on a circuit which is protected by the RCD. The usual culprit is water getting into the wiring - outside light / sockets or a leaking washing machine.

Dave.

 

[bernardgreen]

The RCD will trip OFF when ever 30 mA ( 0.03 amps ) of current is leaking to ground / earth from anywhere in the circuits protected by the RCD

A trip switch or MCB will trip OFF when the current in the circuit that MCB protects becomes excessively high.

Earth leakage can occur in appliances where damp can reach the electrical parts. Unplug any items that were plugged in when the RCD tripped. Unplug as switching OFF will leave the Neutral connected and current can still leak from Neutral to Earth even when the appliance is switched off at the wall socket.

Or it can occur in the wiring of the house in which case an electrician competent at measuring Insulation Resistances is you best option .

 

[NullCipher]

OK thanks both. I guess since its just the RCD that is tripping I can rule out appliances since it was overnight and nothing was on.
The circuits protected by the RCD are the cooker, hob and both socket rings.

I do have an outside socket that went faulty, and it did rain last night. I wonder if that might be the culprit then, although it has rained plenty of times before with no issue.
It sounds like we've had momentary power cuts overnight too, so not sure if that's played a part. Power company said a grounded cable is the cause, but logically I cant see how that trips an RCD on a CU..

 

[aptsys]

I presume you mean MCB rather than RCBO?

You'll only be able to rule out appliances by fully isolating them (plug out or DP isolators turned off).

 

[NullCipher]

Back now so have checked:

Looking at this, the RCCB is what keeps tripping, and RCBO's or MCB's to the right of it don't trip. Pretty sure they're RCBO's though?

 

[ban-all-sheds]

Pretty sure they're RCBO's though?

No, they are MCBs.

You do have one RCBO, and as you can see, unlike an MCB, it says what residual current it will trip on, and it has a test button.

 

[Blueflash]

What's circuit 9 supplying ?

Dave

 

[NullCipher]

What's circuit 9 supplying ?

Dave

It's the shower pump, although not sure what else it's powering though (if at all anything else)

 

[EFLImpudence]

Earth leakage can occur in appliances where damp can reach the electrical parts.

Unplug any items that were plugged in when the RCD tripped. Unplug as switching OFF will leave the Neutral connected and current can still leak from Neutral to Earth even when the appliance is switched off at the wall socket.

 

[Blueflash]

It's the shower pump, although not sure what else it's powering though (if at all anything else)

It's a 16a mcb so it must have a switch fuse connection inline to the pump which will be DP, so you can isolate if required.

Dave

 

[NullCipher]

It does yes.

Saying that though, the RCCB hasn't tripped since I posted this :s

 

[winston1]

It's a 16a mcb so it must have a switch fuse connection inline to the pump which will be DP, so you can isolate if required.

Dave

Why? In Europe circuits usually have 16 amp MCBs and FCUs are non compliant and not available.

 

[DetlefSchmitz]

Interesting... as you are an expert I would be very interested to know which German regulation an [MCB] FCU is not compliant with. Always ready to learn...

Edited to correct silly error.

 

[EFLImpudence]

It's a 16a mcb so it must have a switch fuse connection inline to the pump which will be DP, so you can isolate if required.

It might be a good idea; it might need downfusing (doubtful) - but there is no requirement for local isolation in the regulations.