RCD Trips

[andrew299]

The RCD in my house keeps on tripping. It used to trip regularly (1-2 daily) for no reason and could be reset after sometimes 4-5 attempts over several minutes. At this point I tried testing appliances in different sockets and leaving things off for a few days. There is no pattern and the RCD even trips when all MCBs are set to off - including those connected to the cooker and lighting which as I understand are not even protected by the RCD. The CU s a memera 200AD and the RCD has a rating of 30mA.
Recently the pattern of tripping has changed and now it trips once every other week or so but will not reset for several hours. Again there is no pattern and as far as I can tell no appliance is faulty.
Is there any other checks I can do (Having no practical electrical knowledge other than a healthy regard for my safety) or will I need to call in an electricain and if so what the likely cost of finding this fault?

 

[il78]

I do remember MEM recalling a range of RCD's back because of nuisance tripping, but not to sure which type......could be your one....

Try contacting MEM (memera).....otherwise replace the RCD / Board....

 

[BR]

from what you say it sounds like a faulty rcd, however there are other possibilities. It would be advisable to replace this first. I would consider it a fairly basic diy job. Just wire the new one exactly the same as the old one. Isolate the supply first by tripping the main switch (bear in mind that the cable supplying the main switch is still like so be careful!) Finally ensure you tighten all connections as mush as is possible. (without swinging out of the thing!)

 

[securespark]

And if that fails (so to speak), try finding out which circuit is tripping. Switch off all the mcb's that are protected by the RCD. The RCD should reset. If it does, try switching on all the mcbs that you switched off one by one. If you get to one that trips, thats your culprit. Trouble is, it might not be that easy.

If you find the mcb that trips the rcd is a ring, then unplug or isolate everything on that circuit. Remember things like boilers, garden pumps imm heaters etc..

If the RCD resets when everything is disassociated, then start reconnecting things. Again, when the RCD trips, there's your culprit. Appliances commonly causing RCD trips are the water using ones...boilers, imm heaters, showers, kettles, irons, washing machines, dishwashers, garden pumps etc...........

Bon Chance, as they say en France!!!!

 

[BR]

This is all very well if there was a continues fault on the system, however as the rcd is tripping at irregular intervals, it may not be that simple (I assume that time switches / photocells / sensors have all been ruled out) Also bear in mind that a short between neutral and earth will immediately trip an rcd. Tripping a breaker will only isolate the phase, so a n/e fault would remain in place even with the breaker tripped. Another possibility I have seen is that excessive voltage fluctuations are tripping a ‘non – latching’ rcd (very unlikely in a domestic installation). I still think that a faulty rcd is the most likely problem, however there are more possibilities.

 

[andrew299]

Thank you everybody for your replies
I have tried what securespark suggested already but due to the nature of the fault it is impossible to tell what it is.
I will contact MEM as IL78 suggested as this may mean they send me one free Well I can try anyway!!

Once I have looke into this I will replace my RCD as BR suggested.

Thanks all again

 

[Big_Spark]

One thing to consider, Is the RCD your main switch or is it a secondary switch within a split load board?

If it is a main switch, call an Electrician. If you go breaking the seals on your meter/head fuse to isolate it and it goes wrong you could get prosecuted.

If the electrician does it, it "should" be right and there will be no comeback on you..it will also be safer.

At the same time it would be a good idea to test your installation competely. Get the Electrician to PAT test your appliances.

In the past a minor fault may have been the cause of the nuisance tripping, and this has caused internal damage to the circuits of the RCD, thus resulting in the current problem.

Simply replacing the RCD as faulty and not checking out potential causes may simply be delaying the problem until this RCD fails.

One thing to also consider is that electronic equipment, such as Computers, Hi-Fi and similar kit, in enough quantity on a circuit protected by an RCD, can be the cause of nuisance tripping. This is why IT rooms never have RCD's or RCBO's installed on these circuits.

Large numbers of fluorescent lighting will also cause nuisance tripping, but this should not be a problem in a domestic environment.