The Siemens SIRIUS 3RH1921-2HA22-ZX95 is an auxiliary switch block with 2 NO + 2 NC contacts, designed for snap-on mounting onto a 35 mm DIN rail. It uses spring-loaded terminals for the auxiliary and control circuit wiring, accepting 2x (0.5... 1.5 mm²) with core end processing or 2x (0.5... 2.5 mm²) without. The block is noted for use with 3RT1 contactors, extending the auxiliary contact count on the power contactor or contactor relay.
Ratings and what they mean for fit
The contacts are rated for a maximum of 10 A, with specific current ratings at various voltages: 6 A at 24 V, 6 A at 125 V, 6 A at 230 V, 6 A at 250 V, 3 A at 400 V, and 0.3 A at 220 V. For DC switching, the rated values are 10 A at 24 V, 4.7 A at 60 V, 3 A at 110 V, 1.2 A at 220 V, 0.5 A at 440 V, and 0.26 A at 600 V. The AC-15 rating at 690 V is 1 A, which governs the switching of inductive loads like contactor coils at that voltage. The surge voltage resistance is rated at 6 kV, and the insulation voltage at AC with degree of pollution 3 is 690 V. Contact reliability is specified as 1 faulty switching per 100 million operations at 17 V, 1 mA, which is critical for low-energy signal circuits where oxide films on contacts can cause intermittent failures. The mechanical service life is 10 million switching cycles typical.
Lifecycle and sourcing reality
This part is a phased-out product. The official successor is the SIRIUS 3RH2 series. For a BOM line that requires this exact order code, the part is sourced to order against an RFQ through independent distribution channels. Availability and current pricing are confirmed at quote time. The successor, 3RH2122-2BG40, is a direct-form-fit replacement with spring-loaded terminals and the same contact configuration (2 NO + 2 NC), but note the depth increases from 51 mm to 73 mm and width from 44 mm to 45 mm, so panel layout should be verified before substitution.
Integration and deployment context
Snap-on mounting onto a 35 mm DIN rail means this block clips directly into the standard panel rail alongside the 3RT1 contactor. The spring-loaded terminals accept solid or stranded wire without needing a screwdriver for clamping — strip length and ferrule use per the listed cross-sections. The IP20 protection class on the front means it is suitable for enclosed panels only, not for washdown or outdoor exposure. Operating temperature range is -25 to +60 °C; storage range is -55 to +80 °C. The block is 51 mm deep, 44 mm wide, and 38 mm tall, so it fits within the standard S00 contactor footprint.