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Nuisance Tripping

Postby ldoodle » Tue Mar 04, 2008 9:17 am


Over the last couple of days I have been having my RCD trip out, which in turn disables my breakers for the cooker, shower, upstairs ring and downstairs ring.

It first happened on Friday evening and wouldn't come back on. I unplugged everything from ALL sockets and left over night. Woke up in the morning and it came back on fine. Plugged everything back in and still OK until...

...the same thing happened last night, and again wouldn't come back on. So unplugged everthing again and went to turn back on this morning, but it wouldn't.

As upstrairs and downstairs lights are not on the RCD (but individual breakers) these stay on OK.

The funny thing is that the RCD breaker (which 'controls' the other breakers that are protected by it) wouldn't come back on even with all other breakers in the OFF position.

I'm not an electrician but know the basics of radial/ring mains etc and I have even got a socket tester (live/neutral/earth) and all sockets are fine. I've double checked all connections on the back of each socket and again all seems fine.

Would this indicate a failed RCD breaker or even Consumer Unit entirely. Or could it be more serious?

I have tried to get a few sparkys in but so far no one can do until next week which is no good as i'm on holiday!!

I don't think it's an overload issue as the wiring/appliance use has been exactly like it is for over a year now and has been 100% fine.

Any suggestions?

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Simply Build It

Postby sparx » Tue Mar 04, 2008 8:19 pm

Hi, from the fact that RCD won't reset even with all MCB's 'off' points to a neutral to earth fault. most socket testers can't show this kind of fault up.
If you can get ANY leckie within a week you are doing well!!
we are booked up solidly until end of April!!
The RCD will not trip no matter what load you put on it, it only responds to earth faults not load, that's the job of the mcb's.
turning off an mcb still leaves neutrals in circuit.
The only way to find this kind of fault is to have an Insulation (Megger) check of each circuit in turn with neutrals disconnected from common bar, not a DIY job, also to check RCD needs a tester with ramp test range to check it's actual tripping point, it is always less than the {30mA} rating, but may be much less, any thing can fail eventually,
regards SPARX
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Postby ericmark » Tue Mar 04, 2008 9:06 pm

One thing to add to what Sparx says. The cooker switch is normally of two pole type so switches off the neutral have you tried switching off on the wall rather than the MCB's in the consumer unit. The same applies to immersion heater and central heating boiler and shower. But cookers can absorb moisture from the atmosphere and are allowed to be connected without the RCD protection at the moment but this becomes more of a problem in June. But where there is a 13 amp socket many electricians have connected to the RCD like yours is. If it is the cooker there are special units that can control one circuit on its own called RCBO's which if used at least means when it goes wrong you only lose one circuit but cost about £30 each and need fitting by an electrician.

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