The Siemens 5SM2635-8 is a SENTRON selective RCD unit — a 3-pole residual-current device rated 63 A at AC with a 300 mA Type A trip threshold. Selective (time-delayed) design means it coordinates with downstream RCDs, so a ground fault on a branch trips the local device first without dropping the whole submain. That matters in a distribution board feeding multiple circuits where nuisance tripping costs production time.
Ratings and what they mean for fit
At 40 °C ambient the continuous current rating derates to 58.6 A; at 50 °C it drops to 56.7 A, and at 70 °C it's 50.4 A. If the panel runs hot — say a packed enclosure near a drive cabinet — use the 50 °C figure (56.7 A) as the practical load limit, not the 63 A label. The insulation voltage (Ui) is 460 V, so it's fine on 400/415 V three-phase networks common in industrial and commercial distribution. Surge current resistance is rated 5 kA, surge voltage resistance 4 kV — that covers most utility-side transients on a TN or TT system without external surge protection, though a coordinated SPD upstream is still good practice for sensitive electronics on the load side. Operating frequency is 50/60 Hz, so it's at home on either mains standard. Overvoltage category III and pollution degree 2 are the usual distribution-board ratings — no surprises for a panel-mount device.
Mounting and panel fit
Occupies 3 modular-width units (each 18 mm) on a DIN rail — that's 54 mm of rail space. Depth is 70 mm, so it clears a standard 80 mm deep enclosure without the door hitting the conductors. Mounting position is any, and the supply can enter from top or bottom, which simplifies busbar routing in a crowded panel. IP20 with connected conductors and the distribution board installed — standard for a panel-mounted device; no special washdown rating, so keep it inside the enclosure.