Help choose an RCD for a group of circuit breakers

Michael asks:
Hello. Email the wiring (new) of the apartment is divided into 4 groups: the first and second - four automatic machines for 16A each, VVGng 2-wire wire (no grounding in the house) from the outlet to the distribution box (RC), cross-section 1.5mm2 from RC to electric. flap 2.5mm2. the total length of the wire of each group is 50m. The third and fourth group - three machines on 20A, wire VVGng 2 * 2.5mm2, the length of the wire of each group is 30m. Is it right to install on each group one RCD (total 4 RCD) with a rating of 80A / 30m? Thank.
The answer to the question:
Hello! And you counted 80A by adding the currents of each of the machines? What for? What is your introductory machine? You should understand that you are unlikely to load all 4 groups at full capacity. In this case, the RCD must be the same or one step more than the current of the input automaton. 30 mA in this case should be enough.

But it is not exactly.

What was the total length of the wire? Is 50 meters into 4 groups (automatic machines) or is it connected to each automatic machine of 50 meters? If 50 meters of cable are connected to each of the machines, for example, 1 group, this is 200 meters, here the leak will already be significant. But according to rough calculations according to the PUE from the condition of 10 μA per 1 m of cable length - 10 μA * 200 = 20 mA.

Put on 30-50 mA, in practice, check, because different electrical appliances have different leakage currents. There is evidence that a 10 mA RCD is triggered by FIXED washing machines.

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