The Siemens 5SM2825-0 is a SENTRON residual current unit (RC unit) designed to snap onto a 5SY miniature circuit breaker, creating a combined RCBO assembly. It's a 2-pole, type AC device rated for 63 A at 230/400 V AC, 50 Hz, with a 1000 mA tripping residual current. That 1000 mA threshold means it's sized for equipment protection or fire prevention, not personal shock protection — the standard 30 mA RCD threshold is what you'd spec for personnel. The screw terminals accept solid or stranded conductors from 1.5 to 25 mm², tightened to 2.5–3 N·m.
Current derating and ambient limits
The unit carries a full 63 A up to 45 °C ambient. Above that, it derates: 56.7 A at 50 °C, 54.81 A at 55 °C, 53.55 A at 60 °C, 52.29 A at 65 °C, and 50.4 A at 70 °C. Overvoltage category III, so it's rated for fixed-installation distribution boards, not just downstream equipment.
Mounting position is any — no restriction on orientation inside the enclosure. The IP20 rating applies when the distribution board is installed with conductors connected; that's standard for enclosed gear. Finger and back-of-hand safe protection means the live terminals are shielded from accidental contact during maintenance.