The Siemens SIRIUS 3RT1024-1DB44 is a size S0 power contactor with a 24 VDC magnet coil, designed for switching motor loads in control panels. It mounts via screw or snap-on onto 35 mm DIN rail per EN 50022, fitting a 45 mm wide slot — standard for a three-pole contactor in this frame class.
Ratings and what they mean for fit
The AC-4 rating at 400 V is 12.5 A — this is the contactor's capability for reversing or inching duty where the motor is switched off under full load current. For a 400 V three-phase motor, that translates to roughly 5.5 kW in AC-3 duty (start/run), though the AC-4 figure is the one that governs if your application cycles the contactor while the motor is under load. The built-in varistor surge suppressor clamps the coil's turn-off spike — no external snubber needed for the DC coil circuit. Coil holding power is 5.4 W DC, steady-state, so the 24 VDC supply must deliver that continuously while the contactor is picked up. Short-circuit coordination: for Type 2 (no damage to the contactor after a fault), use a gL/gG fuse rated 25 A. For Type 1 (contactor may need replacement after a fault), the fuse can be 63 A. This is the spec your panel designer needs for the SCCR label. The front face carries IP20 — protected against finger contact. The terminal area is rated IP00, meaning the connection points are not touch-safe when the panel door is open. Pollution degree 3 (conductive pollution or dry non-conductive that becomes conductive) is typical for industrial control panels; no special derating needed for dirty environments.
Mounting and wiring
Screw-type terminals on the main circuit accept 2x (1 to 2.5 mm²) stranded, 2x (2.5 to 6 mm²), or up to 1x 10 mm². The coil/auxiliary terminals take 2x (0.5 to 1.5 mm²) solid or 2x (0.75 to 2.5 mm²) stranded, max 2x 4 mm². Side-by-side mounting is permitted with a 6 mm gap to adjacent devices — no derating required if ambient stays within -25 to +60 °C.