What this part is and where it fits
The Siemens SIRIUS 3RH1344-2BW40 is an auxiliary contactor — a switching block that extends the control-circuit contacts on a main contactor or starter, or works standalone for signal routing in a panel. It belongs to the SIRIUS family, size S00, which is the compact footprint for control loads up to around 10 A. Four normally-open instantaneous contacts give you four independent signal paths; no auxiliary switch, no delayed or make-before-break options on this variant. The 24 VDC coil draws 3.2 W for both closing and holding, so the control transformer or DC supply needs to budget that continuous load per device.
Switching ratings and what they mean for your circuit
The headline rating is 10 A at AC-12, which covers resistive control loads like relay coils, indicator lamps, and PLC inputs. For inductive or motorised loads the contacts derate: 6 A at 230 V, 3 A at 400 V, 2 A at 500 V, 1 A at 690 V. On DC switching the numbers drop faster — 10 A at 24 V, 1 A at 110 V, 0.27 A at 220 V — because DC arcs don't self-extinguish at zero-crossing. The surge voltage resistance is 6 kV, which puts it in the IEC 60947-1 impulse-withstand class for industrial panels. Shock resistance is 10g / 5 ms and 5g / 10 ms, meaning it holds contact continuity under moderate machine vibration but not heavy impact.
Panel integration and mounting
Mounts on a 35 mm DIN rail or with two screws. The 45 mm width is standard for size S00 — it occupies one 45 mm slot in a multi-row enclosure. Depth is 114 mm, which fits most 200 mm deep enclosures with room for wiring. Screw terminals accept 0.25 to 2.5 mm² solid or stranded wire, two conductors per clamp. Mounting position is flexible: +/-180° rotation on a vertical surface, plus +/-22.5° tilt forward and backward. Pollution degree 3 means it's rated for conductive pollution typical in industrial control panels — not clean-room or sealed environments. IP20 on the front protects against finger contact but not water ingress; keep it inside a closed cabinet.