Auxiliary switch for SIRIUS contactors — what the ratings mean
The 3RH2911-4HA12 is a SIRIUS auxiliary switch designed for snapping onto the front of Siemens contactor relays and power contactors in frame sizes S00, S0, S2, and S3. It provides one instantaneous normally-open contact (1 NO) with no leading or lagging switching contacts. For AC-15 duty at 690 V, the rated current is 1 A.
Mechanical and environmental limits
The switch snaps onto the front of the contactor without additional fasteners; the mounting method matches the SIRIUS system for tool-less assembly. Dimensions are 36 mm wide, 43.7 mm deep, and 37.5 mm high. Front protection class is IP00 — the switch relies on the panel enclosure for environmental sealing. Surge voltage resistance is rated at 6 kV. Mechanical service life is 10 million operating cycles typical. The auxiliary and control circuit connection uses ring terminal lugs — confirm the lug size and torque spec from the contactor's wiring diagram before termination.
Mirror contact compliance and documentation
The switch provides a mirror contact per IEC 60947-4-1 when used with 3RT2 contactors — a safety-critical feature that ensures the normally-closed contact cannot close if the main contacts are welded, supporting fail-safe disconnection in safety circuits. Substance prohibitance date is 10/01/2009, indicating RoHS compliance under the EU directive.