RCD's sensitivity ?

MintabiePete · 12 Jul 2005

I am in Australia and have been having trouble with the RCD setup that is on the light circuit . Whenever we get any rain it will trip for no reason . As far as I know there are no leaks on to wires or anything . This is about the 3rd time this has happened over the last 12 months and it has always been when it has been a cold miserable day with rain . One chap told me that sometimes these things do trip for no apparent reason , but it there any way I can check it for sure , or will I have to get a professional in .

Thanks

andy · 17 Jul 2005

MintabiePete said:
I am in Australia and have been having trouble with the RCD setup that is on the light circuit . Whenever we get any rain it will trip for no reason . As far as I know there are no leaks on to wires or anything . This is about the 3rd time this has happened over the last 12 months and it has always been when it has been a cold miserable day with rain . One chap told me that sometimes these things do trip for no apparent reason , but it there any way I can check it for sure , or will I have to get a professional in .

Thanks

only way to test it is with an RCD tester. or test the installation with a insulation resistance tester. these can be done by anyone, but the test equipment is expensive and i doubt youd know how to interpret the results so itll be best to get someone in

MintabiePete · 19 Jul 2005

Thanks for that info Andrew

MintabiePete · 3 Sep 2005

Well it has rained again here , and I have had the same problem again with the Wilco RCBM210/30 clicking off again leaving me with no lights . So this time got the electrician who came around and has just replaced the RCBM210/30 with an ordinary circuit breaker and says he will come around after a week or so to see what happens . Now when I got these devices put in , it was because I had a new line put in for the hot water service and by law here you are supposed to have one of these RCD devices fitted. Now at the same time I got the electrician to put the same type of switch on the other power circuit and the light circuit as a matter of course for protection .Is there any way these Wilco RCBM210/30 devices can be checked , just in case it has been going off for no reason at all , although it is hardly unlikely as the times it has tripped has been when it was raining . For me I would just as soon as put a new device in , or even revert back to the ordinary circuit breaker on the light circuit , would just like to solve the mystery as I have been all over this house and cannot seem to find any area were there is water leaking on to wiring etc.

Thanks

andy · 3 Sep 2005

whats RCBM210/30? (i assume thats the RCD? what ratings is it tho)

its probably water gettin in somewhere causing it to trip. only problem with intermittent faults like that is they can be extremely hard to locate. wait until is rains, and as soon as it trips out, check all fittings for dampness (make sure you have a torch handy!)

you say you are legally required to have an RCD, but what does it have protect? altho it might be a good idea to keep the RCD. changing it for an MCB is only hiding the fault

MintabiePete · 4 Sep 2005

Thanks Andrew for your answer.

Further to the mystery , this morning I tried to switch a light on in the Computer room , and nothing , dead as a dodo , so went out and found the circuit breaker had tripped . It was raining last night , but through the night never switched anylights on , as we have night lights through the house and they show enough light to be able to go to the toot ,and anyway they are plugged into the power circuit . So it would seem that I have a dead short that is activated by rain coming on it . Is the only way to ascertain it for sure to pull off the sheets of tin off the roof and look visually ?

I have tried this morning going around and switching all the lights on , but nothing happened to activate the circuit breaker , I thought that if it tripped I may be able to narrow it down to the actual light that is causing the problem .

The Wilco RCBM210/30 device numbers on it 240v~ 30mA 50Hz and it says Combined RCD MCB on it , but after last night I gather that it works ok .

Thanks