What this part is and what it does
The Siemens 5SM2847-8 is a selective RCD unit from the SENTRON series, designed for 4-pole (3-phase + neutral) installations. It's a Type A residual-current device — catches sinusoidal AC fault currents plus pulsating DC fault currents up to 1000 mA rated tripping current. The 'selective' design means it has a deliberate short time delay (not adjustable — OFF-delay time is fixed) so that downstream RCDs trip first during a fault, keeping this unit as the backup. That's your coordination play: put this upstream of standard RCDs on a distribution board to avoid a whole-panel blackout on a single branch fault.
Ratings and what they mean for your panel
Rated 100 A at AC. Derates to 93 A at 40 °C, 90 A at 50 °C, 80 A at 70 °C.
Mounting and integration
Snap-on DIN rail mount (REG fastening method), 5 modular width units. Dimensions: 124 mm wide × 90 mm high × 70 mm deep. Mounting position is any, so you can orient it horizontally or vertically in the panel if needed. Power supply can enter from top or bottom. The unit is designed for the 5SP4 distribution board series but fits any standard DIN-rail enclosure with the right cutout. Not sealable — no padlock hasp for lockout/tagout on the device itself.