Advice Please

[Jim Philbin]

I'm no electrician but normally a reasonably competent DIY'r. My sister has an electrical problem that I don't understand so maybe someone can help, it would be much appreciated.
The main 63Amp trip is continually tripping out. I've tried isolating a faulty circuit by switching OFF the individual MCB's but it trips inconsistently on a whole variety of MCB's. Sometimes it stays ON for quite a while then eventually trips again for no apparent reason. I replaced the 63Amp trip but the problem has remained the same.

I'm able to work safely as there is a separate incoming mains isolator switch.

Jim

[Ohmslaw]

Do you have access to an insulation resistance tester???

If not I suggest you contact a qualified electrician.

[JohnC]

Im guessing that your reffering to a 63A 30mA RCD, If it is tripping off randomly with different MCB's turned off then it would suggest that its a Earth to Neutral fault so turning off MCB's wont help as they only isolate the Live. You would need to disconnect and test the neutrals.

A couple of things to try first would be un-plugging appliances, usual suspects can be fridges, kettles, washing machines, toasters. Does it trip off at any particualar time, After its been raining. when several appliances are turned on around the same time.. And most importantly has any work been carried out recently. even things like hanging a picture up can cause a problem if a cable has been hit.

But as Ohmslaw said there is only so much you can do without actually testing the cables.