UK Rcd tripping

[Steve1968]

Hi
I was called to a job where the rcd was tripping after a power cut. I have tested the circuits connected to it and all ok. I have tried turning the consumer unit off and on but rcd stays on. Would a power surge when power is re-energize cause this.
Any suggestions would be helpful.
Thanks
Steve

 

[Cid]

Have you tested the RCD?

 

[littlespark]

You said rcd trips, but later saying it stays on? What’s the actual fault here?
As above, get your rcd tester out

 

[Steve1968]

Ok tested rcd seems ok. I meant when I turned the consumer unit off to simulate a power cut it didnt cause the rcd to trip that is why i was wondering if a power surge when power is re-energized could cause it to trip.

 

[littlespark]

It depends what was all switched on during the powercut that might not have been on when you simulated the action.

fridges, freezers and whatever may have been on or off depending on the status of their thermostats.
The power coming back on may have surged and blown a lightbulb, which can trip an rcd.

RCDs are sensitive little things.

I don’t think there is a problem, but if it’s only one rcd for the whole board, accumulative earth faults etc.... I’d recommend individual rcbo for each circuit.

 

[Wilko]

Hi - if I’ve understood correctly, your Customer has reported there was a power cut, following which there was a period where the RCD was tripping, but it then settled and now works and tests ok with no fault found in the installation(?) . I have had this behaviour reported where DNO was having network issues. I’ve never been on site to test when it was happening, but I think it may be down to their N momentarily flicking away from the local E as network switching is happening. Any signs of this behaviour now and all bets are off .

 

[Dabbers]

lazy RCD comes to mind I bet since the day it was installed its never been tested do a RCD ramp test and see what current it is tripping out at?

 

[multimick]

had a few calls were rcd has tripped after power restored ,it always resets ok ,no idea what causes it .

 

[scootknew]

somtimes when rcd hasnt been tested with the button in a long time it can trip easy. when its feeding heavy load like cookers, showers etc. even a light bulb blowing can trip it. first turn off all breakers then power on rcd . then one by one switch mcb;s back on. in my experience replacing the rcd to new solves it 99% of the time. unless its an older property with really bad old wiring then better get your thinking hat on.

 

[HappyHippyDad]

When you say the RCD tested 'ok', what did it actually test as? Trip times and ramp?
If the RCD tests fine and all IR tests are fine, along with an acceptable earth leakage test and the only problem is that it has tripped once after a power cut, then I would say your job is done.