Earth Leakage Tester, what should trip, MCB or RCCB? France

I've just wired my workshop and bought an earth leakage tester to check the sockets were wired correctly, they were.

When I tested the sockets they all trip the RCCB rather than the MCB at either 25 or 30mA. Is this normal?
It is the same with the sockets that I have tested in the house.

The consumer unit was installed by an electrician, all I have done is added 3mcbs ( Lights, sockets, and one for the heater). I've used 3 core, 2.5mm2 rigid cable for the sockets connected to a 20amp MCB (8 sockets). The consumer unit has a 40A 30mA RCCB.

Many thanks

Andy

MCBs are designed to protect a circuit against over-loading if too many devices are connected to it, or if there is a direct live to neutral short. This is what protects your house from burning down.

The 20amp MCBs will trip if loaded beyond 20amps. They have a trip curve, which means that they will safely continue to operate for a little while if overloaded slightly before they trip where as with a serious overload / direct short they will trip fast. This is so that they can cope with motor start up surges etc.

RCD (RCCB) is designed to prevent electric shock. They trip if the difference between live and neutral is more than 30mA (or, whatever the preset value is).

Your earth leakage checker causing an earth leak i.e. it's connecting from the live to the earth and your RCB trips. This is perfectly safe and normal and what should happen.

Your MCBs will only trip if the circuit's overloaded or there's a straight live-neutral short circuit.

There's a small French distribution board:



Btw : NEVER EVER EVER use 32A rings in France. They can only be used with fused plugs i.e. UK / Irish type plugs and sockets.