Switzerland being what it is, there may be differences in installation practice from one canton to another, but I'm surprised you have a 3P16A installation. My understanding is that the 3P supplies are all 10A supplies. My greatest concern would be the wiring which will almost certainly not be rated at 16A.
Strictly speaking I don't think you're supposed to break up the phases that way, but I don't see that really being a problem.

All implementations break up the phases that way! (how else would you do it?) Each phase is 230V to neutral.

Also, just checked, both 3P outlets in the kitchen are 16A (as is my office at work), the remaining 3P circuit for the rest of the apartment (lights, etc) is 10A.

Tom

Of course not.

I will connect the oven to a 3P16A CB (one phase only though), which will be replacing the old 3P10A CB as I need two 3P16A CB's - one for oven and one for stove and replace the wires from the switch board to the outlet to 2,5 mm2......all good.

Hey Tom,

Glad to hear you have same config as in my Geneva apartmt. As attached in the pics, the breaker box shows 380v-415v with and 3 CBs showing 16A for kitchen and the rest are 10A. This is a 3phase I believe.

Only issue I have is this:

The german kiln I plan to buy is 4.8kW. It works either with a 5-pin (3 phase) plug with 7 Amps or with a 3-pin (1-phase) plug with 21 Amps.

if the kiln is converted to 3pin, it should still work on this 3ph circuit, right?

Any help is appreciated.

Thanks
Mani

No, you need to use a three-phase plug, which is usually 5 pin (3P,N,G), though some older plugs are 4 pin (no G).

Tom

Many thanks for the confirmation!!!