The Siemens SIRIUS 3RH2911-4FB22 is an auxiliary switch block that snaps onto the front of SIRIUS contactors in frame sizes S00, S0, S2, and S3. It provides one normally-open instantaneous contact and one normally-closed lagging contact, with a leading contact also present. The ring terminal lug connection suits panel wiring where secure, vibration-resistant terminations are preferred over cage clamps.
Ratings that matter for the panel builder
The AC-12 rated operational current is 10 A maximum, which covers most control-circuit loads like PLC inputs, relay coils, and indicator lamps. For inductive AC-15 duty at 690 V it is rated 1 A — the figure to use when switching contactor coils or solenoid valves on a 690 V control transformer. The DC switching table is detailed: 6 A at 24 V, 2 A at 48 V and 60 V, 1 A at 110 V, 0.9 A at 125 V, 0.3 A at 220 V and 250 V, and 3 A at 400 V. These are the values that govern whether the switch holds its arc on a DC inductive load; the 24 V 6 A rating is typical for a 24 VDC control bus feeding multiple small relays.
Snap-on mounting to the contactor front means no DIN-rail space is consumed — the switch rides on the contactor itself. Dimensions are 36 mm wide, 37.5 mm high, and 43.7 mm deep, so it protrudes about 44 mm forward of the contactor face. The front protection class is IP00, so it relies on the enclosure for dust and moisture protection. The switch is not a mirror contact per IEC 60947-4-1, so it should not be used as the sole feedback for safety-related contactor weld monitoring in a safety circuit.