Friend of mine mentions that the place he is staying in has a earth leakage that he thinks is not working right. So I am there but have no tools and he at least has a semi decent multi meter. I press the test button as he has done and it trips. Reset it and try again - nothing. Ok. Easiest way to test earth leakage undo everything at the bottom and take a piece of wire and touch from neutral to earth. Doesn’t trip but creates a small arc. I think to myself ok thats not right. Take the multimeter and test. I get the full 230v between the neutral and earth after the earth leakage but before the earth leakage its round about 10v. Not knowing if his tester is ok or not I get a normal cfl bulb and touch one point to the metal casing and the other one to my wire. It lights up but flickers. I then disconnect the neutral at the top of the earth leakage and connect a wire from the earth bar to the top of the earth leakage and do the same touching the cable from the bottom (which now should be a earth) to the one point of the lamp and the other point to the metal of the db which i did check was connected to the earth bar. It lit up ! What is going on here ? How can I get a voltage thats strong enough to light up a lamp between earth and earth by just passing it trough the earth leakage ? I reconnected everything as I found and told him to be very careful until I can have a decent look at just what is causing this strange fault.