What this 4-pole RCD does on the line
The Siemens SENTRON 5SM2646-0 is a 4-pole residual current device (RCD) rated for 63 A at AC and a tripping fault current of 300 mA, Type AC — meaning it detects sinusoidal AC residual currents only, not pulsating DC or smooth DC. Instantaneous design means no intentional time delay; it trips as soon as the residual exceeds the threshold. This is the unit you spec for a 50 Hz, 400/460 V distribution board where the load is resistive or standard motor-driven and the installation requires overvoltage category III and pollution degree 2 conditions.
Ratings that decide the fit
The headline 63 A AC rating is at the reference ambient — but the part derates in warmer cabinets: 58.6 A at 40 °C, 58.59 A at 45 °C, 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. If your panel ambient runs above 40 °C, the continuous load must stay under the derated figure for that temperature. The 300 mA residual threshold is fixed — not adjustable — and the OFF-delay is not adjustable either, so this is a straight instantaneous trip, not a time-delay S-type unit. Insulation voltage (Ui) is rated 460 V, surge voltage resistance 4 kV. The operating frequency is fixed at 50 Hz. Mechanical service life is 10 000 operating cycles typical. Power loss per pole in hot operating state is 3 W — four poles total 12 W heat dissipation inside the enclosure, which matters for thermal budgeting in a sealed panel.
Mounting and panel fit
Occupies 3 modular width units (each 18 mm) on a DIN rail — 54 mm total width. Fastening method is REG (regular DIN-rail clip). Mounting position is any orientation. Depth is 70 mm, height 90 mm, width 123 mm overall. The protection class is IP20 only when the distribution board is installed with connected conductors — not rated for washdown or outdoor exposure without an enclosure.