Tempremental RCD - why?

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Hi,

Our consumer unit has fuses for each circuit, with the main switch for the whole supply being an RCD.

All usually works well, apart from if we have to turn the power off for any reason, and particularly if any work is carried out on the wiring. Then the RCD becomes extremely temperamental and will trip when turning on things like the kettle, vaccum cleaner, lights (but only the LED ones in our kitchen).
It sometimes wont resent unless all the fuses are pulled, it'll then reset OK and not trip when the fuses are put back in, and all is well until we dare turn something back on!

The 'cure' seems to be to put the power back and turn as little as possible on for a few hours, and then all is well.

If we have a power cut, the RCD invariably trips when it comes back on. In these circumstances the RCD will usually reset and we have no problems with it tripping when we turn lights etc on.

The last time we had this problem, I'd turned the power off to replace a double socket with one that contains 2 USB charging ports. Eventually after double checking my connections and resetting it for the umpteenth time it seemed to settle down.

This morning our recently replaced heating pump stopped working. I turned the power off to check the connections in the terminal box that the pump is wired into. I did find one wire that was possibly loose. Turned the power back on, hey presto the pump works again (although it could just as easily have been a stuck relay etc I guess).
Went into the kitchen, turned the lights on, clunk as the RCD tripped.
Reset.
Turned on the wall lights in the kitchen. All fine.
Turned on the LED lights (that had just caused it to trip). All fine
Heating and boiler running, fridge running.
Cooker working fine.
Turned the kettle on. RCD trips.
Reset (had to pull all the fuses to get it to reset).
Cooker etc all working.
Wife turns the LED lights on. RCD trips.

I've reset is (having pulled the fuses again to do so and put them back in one by one). I've left for work with wife cooking her breakfast and told her to not use the LED lights or kettle for a few hours.

Last time we had this problem we were convinced the vacuum cleaner was faulty until we realised that other random things were causing it to trip.

What could cause this problem? If it was a wiring fault then surely it would always trip rather than "sorting itself out" after a few hours?
If the RCD was faulty then again I can't understand why it would start behaving itself after a while.
It might be filters etc on various electronic circuits such as the LED lighting, but then again why would it only manifest itself as a problem when the power is first turned on?

It's baffling. Any advice most welcome before I call an electrician out. We did get them to check it out when they wired our kitchen extension (the problem existed before that work) but they said all was fine.
Is it worth replacing the RCD or could there be more of an in depth problem?
 
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Check the leakage current, maybe it's high enough that the RCD is right in the edge.
Could be a case of subdividing the circuits into more rcds
 
Thanks for the reply. Why would the behaviour change in that case? It doesn't ever trip, other than when we've turned the power off for whatever reason at which point it becomes a nuisance.

I guess if the fuses are replaced with RCDs the main switch should be changed to just a switch rather than an RCD? Otherwise the total leakage will still trip it.
Is replacing the fuses with RCDs something that you are allowed to do as a DIY job?

Mrs has just called to say it's still tripping randomly ever hour or so. Bet I can't get an electrician out for days!
 
Why would the behaviour change in that case? It doesn't ever trip, other than when we've turned the power off for whatever reason at which point it becomes a nuisance.
According to the spec it must but trip at 15ma, it must trip at 30. If you're between that then it may or may not trip.
The leakage needs checking, the cause investigated and if it's genuine natural aggregate leakage then separate RCDs can be fitted.
 
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Ps you can do it DIY but the testing would be impossible without the right tool. You'd really need to notify building control.
Basically it's one of those things if your have to ask, the answer is probably no.
 
Thanks again, I thought that might be the answer!
I'm not going to attempt it myself, not worth the risk for the potential monetary saving.

It's a damn nuisance at the moment though!
 
PS. If I hold the RCD on, the power stays on. I think if there's a fault the RCD should trip even if somebody jams the switch in the on position?
Just wondering if perhaps the RCD is faulty?
 
PS. If I hold the RCD on, the power stays on.
Well, it would, wouldn't it?

I think if there's a fault the RCD should trip even if somebody jams the switch in the on position?
Do you? How would you then turn it on again?

Just wondering if perhaps the RCD is faulty?
Could be. Might be something else.

You need someone to test it.
 
Well, it would, wouldn't it?


Do you? How would you then turn it on again?
.

I hadn't really thought about how a circuit breaker should work if you turn on with a fault present, but if you have a short on an MCB you'd want it to trip immediately regardless of where you hold the lever. Is that not the case in the situation of MCBs either? I realise this particular case is an rcd

Otherwise I could imagine propping up the lever with a bit of wood would be the modern equivalent of replacing the fuse with with a bit of CPC.:whistle:
 
I was thinking along the same lines as John. I think there's a spring loaded mechanism which allows the trip to function even if the switch is jammed on. Flipping the switch to off resets the mechanism.

Anyway, electrician coming out tomorrow mid morning. Just got to try and keep the essentials on until then.
 
I would think it is faulty, then.

Not really tripping because of a fault - just a worn latch or something like that.
 
I was thinking along the same lines as John. I think there's a spring loaded mechanism which allows the trip to function even if the switch is jammed on.
Yes, having just tried mine, you are right.

Flipping the switch to off resets the mechanism.
Yes, it must re-engage somehow.
the switch seems to be sprung (to off) as well so that it goes down when let go,
only held up when on by the mechanism.
 

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