RCD keeps tripping.

[martin8cs]

Please help. Pretty desperate. We've just had a pretty bad storm in Ilford and all our electrics blew. On investigation I discovered that the RCD is blowing when we flick the fuse for the kitchen and utility room. If that is off the other fuses in the fuse box can remain on. Trying to contact an electrician we use but he's not available at the moment.

We've unplugged everything and it still blows.

Help please for an uneducated householder and if I can contact my electrician is it likely to be expensive?

 

[deadshort]

If you have any outdoor sockets or lights on that circuit they need to be swiched off or isolated. Switch off and unplug all appliances on that circuit and try to reset the rcd.

Regards,

DS

 

[sparkwright]

To clarify, there could be moisture inside an outdoor socket or outdoor light.

 

[martin8cs]

Thank you. As far as I know the particular fuse that keeps tripping only does the utilities. But I'll check now, thank you.

 

[martin8cs]

I've checked. Can't think of any outside lights on that circuit. Slight improvement now in that the RCD doesn't trip immediately - now electrics stay on for 10-20 seconds so maybe water has got in somewhere and is drying out now the storm has passed. Thank you both for your help.

 

[bernardgreen]

The fault, probably water ingress, can cause the RCD to trip even though the MCB for that circuit is switched OFF. The MCB disconnects only the Live while the Neutral remains connected.

Neutral_Earth_trip

• bernardgreen
• 16 Jan 2011
• 48

Although switching ON the MCB for the utility circuit is cauing the RCD to trip the actual fault is on a circuit on a different MCB

 

[martin8cs]

Not sure I fully understand the techie bits but I think you're saying to me that the fault could be somewhere other than the circuit that is actually tripping out.

Managed to contact my electrician. He's coming over Wed so thank you all for your help.

 

[bernardgreen]

but I think you're saying to me that the fault could be somewhere other than the circuit that is actually tripping out.

Yes, switching on the utility room MCB and then switching on an appliance in that room will cause some current to flow through the fault that is on another circuit whose MCB is switched OFF. That current through the fault is the reason the RCD trips. Not all electricians realise this and may spend a lot of time looking on the wrong circuit for a fault that isn't on that circuit.

 

[sparkwright]

Utilities?

Any washing machines etc still connected?

 

[Taylortwocities]

Is the boiler/heating system on that circuit? Faulty pump/valves can cause this.
Make sure that is isolated - a common cause of RCD tripping is places where elctricity and water are close together.

 

[martin8cs]

Thank you to everyone who replied. Whatever the cause was, all the power is back on. Because it happened during a massive storm I'm going to ask our electrician to check all the outside lights in case there is a water leakage somewhere (I need to change two anyway).

Your help has been invaluable, not because I was able to do anything (I'm a DIY disaster) but because you put my mind at ease that it didn't have to be something major (=majorly expensive) to put right.

 

[Taylortwocities]

It rarely is anything expensive. The cost is usually in the time taken to find out what is causing it.
A fault that is there all the time is easiest to find, one that happens 'now and again' is the more difficult to locate.

Sometimes it's a put on the deerstalker hat and light the pipe situation.