Many countries require the use of at least two RCDs these days. In Germany that seems to have caught on but in Austria not quite, the only home box with more than one RCD I've ever seen was mine. And I only did that because it was a really fancy place. The new kitchen alone got seven circuits for a 3-phase induction hob, electric oven, dishwasher, microwave, combi boiler, lights and sockets. Originally (1960) there were only two, lights and sockets. And that was fancy, usually lights and sockets weren't on separate circuits back then.
In a larger place I'd absolutely do one RCD per floor so no one has to stumble down stairs in the dark. Even that's a bit unusual though.
RCBOs are still painfully expensive. I think a 2-pole RCD is around 30 Euros, an MCB around 10 and an RCBO is 70 Euros. I only bought some recently because they were 60% off. Hardly comparable to the UK where you can get an RCBO for 10 to 20 quid off eBay! Sometimes actually the same brand that costs more than twice as much here...
What does RCBO and MCB stand for? Im none to familiar.
