RCD random tripping

[number49]

Hi all,

Our RCD had tripped this morning shutting down the consumer unit.

Resetting the RCD and leaving the 'house socket' breaker off results in everything else working fine.

The kitchen appliances I thought would be likely to cause issues such as the fridge, washer, kettle etc are on a separate breaker to the house sockets and are definitely not the culprits as they work fine with the house socket breaker off.

If I reset the breaker for the house sockets sometimes it retrips the rcd instantly sometimes it stays ok for anywhere from a few mins upto an hour before it trips again with the tv, a phone charger and radio alarm clock plugged in.

I unplugged all sockets and tried resetting then plugging in one by one, but there doesn't seem to be one specific appliance that causes it. And no logical sequence to when it happens.

No changes have been made to the circuits recently and no other diy that I can recall which would disturb/damage the electrics.

Any ideas/advice on finding the likely cause greatly appreciated


The RCD is labelled as a contactum b8003/2.

 

[EFLImpudence]

Is the boiler on this circuit?

Any outside lights or sockets that could be wet?

 

[number49]

Nope. The boiler is on the kitchen sockets circuit along with one outside light. The other outside light is on another separate circuit.

As far as I can tell the only things on the suspect circuit are internal sockets which are used for the tv, DVD, pc, phone chargers and intermittently for the iron and Mrs's hairdryer etc.

We're pretty mindful of turning things off as we go so can't see us overloading either.

Will a plug in socket tester show if its a L-N fault at the sockets to rule out a loose/poor connection without dismantling all of them? Never used one before.

 

[ericmark]

I will try to explain how it works. With a leak from line to earth invariably the faulty appliance will trip the RCD when it is used.

But with a leak from neutral to earth while no current is being drawn the voltage between neutral and earth is the same. So with no voltage differential no current flows.

As the load increase so the voltage on the neutral moves away from the voltage of the earth wire so any leak between neutral and earth will start to take current.

For the electrician the job is easy either a PAT tester or an insulation tester will test each item but for house holder the job if harder. What you need is to introduce a load at the furthest point of the ring so that the is a voltage differential between neutral and earth. And a good load like an electric fire.

So if the fire trips the circuit with nothing plugged in but is OK in the kitchen then the fault is in fixed wiring. That an electricians job. If however the fire runs OK then you can start with the fire running to plug in other items. Hopefully the faulty one will then be apparent.

 

[bernardgreen]

A Neutral to Earth fault in fixed wiring that trips the RCD when a load ( lectric fire etc etc ) is switched on may not be on the circuit that has the load on it.

Neutral_Earth_trip

• bernardgreen
• 16 Jan 2011
• 48

To find these Neutral to Earth faults requires measurement of insulation resistance on ALL circuits as there can be more than one Neutral to Earth fault. That needs an experienced person with the necessary test equipment to measure the insulation resistance.

 

[number49]

Thanks for the responses the diagram helped alot.

Somebody's coming to trace the fault on friday, fingers crossed it's not too well hidden...