Selectivity and derating — the numbers that decide the panel design
This is a selective (time-delayed) RCBO, energy limiting class 3. That means it rides through short-duration inrush and lets downstream MCBs trip first — essential for a distribution board feeding multiple sub-circuits where you want only the faulted branch to open. The trade-off is a wider body: 11 width units (198 mm wide, 90 mm tall, 77 mm deep, 70 mm installation depth) on the DIN rail. Mounting position is unrestricted, and the supply can land on either top or bottom terminals. Derate linearly: 115.6 A at 40 °C, 111.3 A at 45 °C, 106.3 A at 50 °C, 101.3 A at 55 °C, and 96.3 A at 60 °C. Overvoltage category III means it's rated for fixed-installation supply-side duty. Terminals accept 6 to 50 mm² solid or stranded copper, which covers the full range for a 125 A feed. Touch protection is built in; IP20 is maintained once the distribution board is installed with conductors connected.