I'm trying to wrap my head around the way in which to implement a three phase distribution board that suits my requirements ... requirements which are by no means unusual. I need three phases only for the pump of a heat pump. The whole of the rest of the system can be single phase. From the meter, a four core cable comes into a 4 pole isolator. That's fine. I don't want a three phase RCD there, as I don't want the whole house to go down just because the heat pump motor trips it or if any one of the phases used as monophase trips it. I therefore need a three phase RCBO for the heat pump motor. I also need EITHER three single phase RCDs (one for each of the balanced loads going to the rest of the house) OR a single phase RCBO for each of the circuits in the rest of the house. So, nothing complicated about all that. My current plan for the physical implementation in the three phase distribution box is as follows: The 4 pole mains isolator sits at the bottom, and it feeds the two vertical columns. On the left column I will mount a 3 phase RCBO for the heat pump motor. On the right column I will mount RCBOs on each of the phases in a balanced way to feed each of the existing circuits in the house. If there are too many single phase circuits for the right column, I can use any remaining single circuits on the left column, and blak the rest. I assume this is how things are done nowadays (now that RCBOs are cheaper than they used to be). How would it be done if I wanted three single phase RCDs? I have been looking at Hager products. Does anyone have any thoughts on whether they're a good choice or not? Are there any other vendors I should be looking at? (Schneider? Legrand?) FWIW this is all going to be done in France, so please don't let's start the usual finger wagging exercise of telling me off because all this is notifiable. It's in France, so it's not. The electricity supplier upgraded the property to three phase yesterday and they didn't even bother to check what they were connecting to.