Either the circuit or the aircond or the switch itself is shorted/leaked.

8 out of 10, it cannot be the aircond, the aircond itself that is broken. When the aircond sometimes works it is not the aircond. It could be the wiring.

When was this happened the first time? After installing the aircond? The aircond just installed recently?

When is this most often happen? During raining day? If during raining days the wire outside to the compressor shorted as rain water conduct the leakage.This is more so the leakage is not high. If high the MCB should trip instead of the main ELCB(the blue switch) where live touches neutral. ELCB trip when leak to earth happens like live wire touches earth.

This lead to another question. What is the rating of the MCB? 10A, 20A, 32A? and do you know whcih one in the first place?

Aircond installer vs electrician !!!!

The electrician lay cable from main to the switch and to the aircond indoor unit. To test this circuit is to disconnect the aircond indoor unit supply and connect the 3 wire (live, neutral and earth) to a power point and use a fan plug it on and swtich on. If no trip the circuit is ok, the electrician can go home otherwise it is clearly his fault. Then get the aircond installer and get him to pull a new cable from the indoor unit to the out door unit.

Ya, on sunny day the water is sticking there, not completely dry yet.

MCB. see this C32. C for current i think.

I think he dont fully understand what we are talking about.

Maybe this is a little easy to understand. When ELCB trips it is because there is a current leak. And the leak most likely is somewhere between the indoor unit cable that connect to the out door compressor. The cable could have been cut but not broken. The cable has 3 wires inside. When water get into the cut cable, current take a short cut, flow/jump from one of the exposed (cut) wire to another its nearby exposed (cut) wire and when this happens the ELCB trip. Another leak is the cut/exposed wire when wet some current flow to the wet wall down to the earth and the ELCB trips.