The Siemens 3RH2422-1BW40 is a SIRIUS auxiliary contactor in size S00, fitted with two instantaneous normally-open contacts and a 24 VDC coil. Its job is to switch control signals — pilot lights, PLC inputs, contactor coils, or small solenoid valves — in a panel where the main contactor or motor starter has already handled the power circuit. The 4 W closing and holding power means the coil draw is modest; a standard 24 VDC control transformer or a PLC digital output can drive it without a separate interposing relay, provided the output's minimum load current is below the coil's holding current.
The 10 A rating at 24 V and at 230 V governs the resistive load curve — a 24 VDC pilot lamp bank or a 230 VAC contactor coil falls within that envelope. At 400 V the rating drops to 3 A, and at 690 V to 1 A, so if you are switching a 400 VAC control transformer primary, stay under 3 A. The 2 instantaneous contacts are not timed or delayed; they close and open with the armature travel, so they suit straightforward interlocking and status feedback, not sequenced logic that needs a timing relay.
The S00 footprint is the smallest Siemens contactor frame; the 3RH2422-1BW40 measures 73 mm deep by 90 mm wide by 57.5 mm high.
Mechanical endurance is rated at 5 000 000 operating cycles, which for an auxiliary contactor running at, say, 10 000 switching operations per hour translates to a service life measured in years before the contacts wear out, provided the load current stays within the rated curve.