What it is and what it does
The Siemens 3RH2344-1DM40-0KA0 is a SIRIUS auxiliary contactor, Size S00, with 4 instantaneous normally open contacts. It is designed to switch control circuits — signalling, interlocking, and logic-level loads — in motor starter and contactor assemblies where the main contactor's own auxiliary contacts are already consumed or where additional isolated contact sets are needed. The coil is rated 24 V DC with an integrated varistor surge suppressor, closing power of 4 W. The rated control supply voltage is 220 V, with an operating range of 0.8 to 1.1 times the rated value — meaning the coil must see at least 176 V and no more than 242 V to pick and hold reliably. Mechanical endurance is rated at 10,000,000 operating cycles, and the AC switching frequency is 10,000 operations per hour. The arcing time on DC loads is 7 to 13 ms; overall arcing time is 10 to 15 ms.
Contact ratings — what they mean for your circuit
The 4 NO contacts carry rated operational currents that vary with voltage, reflecting the switching capacity across different control voltages. At 24 V the contacts are rated 10 A; at 60 V, 4.7 A; at 110 V, 3 A; at 220 V, 1.2 A; at 230 V, 6 A; at 400 V, 3 A; at 440 V, 0.5 A; at 500 V, 2 A; at 600 V, 0.26 A; and at 690 V, 1 A. These are not continuous thermal currents — they are switching ratings per IEC/EN 60947-5-1 for utilization categories typical of control circuits. The 10 A at 24 V, for example, covers most PLC output and relay loads; the 1.2 A at 220 V is adequate for signalling a contactor coil or indicator lamp. The drop at 600 V to 0.26 A reflects the reduced switching capacity at higher voltages for the same contact gap.
Mounting and integration
Fastening is by screw or snap-on mounting onto a 35 mm standard mounting rail (DIN rail). The Size S00 footprint is 45 mm wide, 57.5 mm tall, and 117 mm deep — a compact envelope that fits alongside S00 contactors in a motor starter row. Mounting position is flexible: +/-180° rotation is possible on a vertical mounting surface, and the device can be tilted forward and backward by +/- 22.5° on a vertical surface. Clearance distances to adjacent components: 10 mm upwards, 10 mm forwards, 10 mm downwards, 6 mm at the side. Conductor cross-sections accepted: 2x (0.5 to 1.5 mm²), 2x (0.75 to 2.5 mm²), or 2x 4 mm², solid or stranded. Degree of Pollution 3 per IEC 60947-1 — suitable for industrial environments with conductive pollution.
Environmental and compliance
Operating temperature range is -25 to +60 °C; storage temperature range is -55 to +80 °C. Relative humidity minimum is 10%. No auxiliary switch extension is available on this variant; the 4 NO contacts are fixed. The product designation is auxiliary contactor, not a main power contactor — it switches control circuits, not motor loads.