In = 40A / 63A indicates the Max carry amp of the RCCB. It means, if you install a 40A RCCB, but you are running 50A of load, it will trip. This protect from overload.

Ioan is the sensitivity of the RCCB. Ideally, Live + Neutral = 0, if Live + Neutral /= 0, leakage happen. But, there's no ideal in real life, so, comes the Ioan where it is the tolerance the device will accept before registering the leakage as a fault, in your case, 100mA.
Generally, for lighting circuit, 100mA is used, 30mA is used for power circuit and 300mA for Air-Con.

As for your problem, how old is your house, particularly, the electrical wiring? The older the wiring, the higher the probability of leakage through wires due to degration of the insulator.

Proper solution, do a complete insulation test to the whole house, or change all the wiring. Improve your house earthing system.

Cheap solution, which profesional do not agree, but client will usually do due to cost saving. Use higher tolerance RCCB or use ELCB instead.

No matter how do it, make sure other than the fuse, there's at least a protection device in place.

Insulation test is very tedious job. Have to dismantle all lighting and power point from its appliances, and it might damage your existing wirie insulation since during insulation test, 1kV(can set to 500V) will be injected to the circuit to stress the wiring. If your wire insulation "almost going to die" after the injection, most probably going to "die" for good. We only do insulation test if the house wiring is still new, or when we know which particular circuit giving the problem. Not to mention, i don't think your local neighbourhood electrician know what is "insulation test".

RCCB are replacing ELCB and both are two different thing with different protection method which you can easily google it up.

One of my suggestion is to improve the earthing system as well. But it will involve lots of $$ especially lately where copper price are still at it high side.


As i suggested earlier to helob, either change the house wiring, use less sensitive RCCB, use back the primitive ELCB, improve your earthing system, or change to other protection system such as using adjustable ELR with a shunt trip coil, or just leave it as is, standby at the DB during thunder.

MCB detects overcurrent. Say, a 2.5HP aircon connected to 10A MCB, MCB will trip.
ELCB detects if any current running in the Earth conductor
RCCB detects residue current between L&N.

Earth Resistivity (Electrical Grounding) test using Earth Tester. Calculated in Ohm, the lower the ohm the better it is.

Insulation Tester (Mega Tester) is test the insulation capability of the cables. Measured in MOhm. The higher it is, the better.

Both Earth tester and insulation tester are not cheap at hundreds.