The Siemens SIRIUS 3RH1921-2DA11-ZX90 is a first lateral auxiliary switch block delivering one normally-open and one normally-closed contact, terminated via spring-loaded terminals. It is designed to snap onto 3RT1 contactors, adding auxiliary signaling or control feedback directly on the contactor's side. Rated at 10 A maximum, this block handles 10 A at 24 V DC and 6 A at 24 V AC, with derated switching capacity at higher voltages: 4.7 A at 60 V, 3 A at 110 V, 1.2 A at 220 V, and 0.5 A at 440 V. The 6 kV surge voltage resistance and 500 V insulation rating (pollution degree 3) mean it holds up in industrial panels with transient-heavy loads. Contact reliability is specified at one faulty switching per 100 million operations at 17 V, 1 mA — a figure that tells you this block is suitable for low-energy PLC inputs or safety circuits where a dry-contact failure would be hard to diagnose. The mechanical service life of 10 million switching cycles aligns with the contactor it mounts on.
Mounting and integration
Snap-on mounting to the 3RT1 contactor frame — no tools, no DIN rail. The 10 mm width keeps the assembly compact; the 71 mm depth and 72.5 mm height match the contactor envelope so the auxiliary block does not protrude beyond the contactor's own footprint. Spring-loaded terminals accept 2x (0.5 to 2.5 mm²) without ferrules, or 2x (0.5 to 1.5 mm²) with ferrules, plus 2x (20 to 14 AWG).