What it is and what it fits
The Siemens SIRIUS 3RH2911-2XF12-0KS1 is a solid-state compatible conventional auxiliary switch block designed for contactor relays and power contactors in the S00 frame size. It snaps onto a DIN rail and provides 2 NC plus 1 NO contact set, with the NC contacts specifically rated for solid-state load compatibility — meaning they handle the low leakage currents of PLC outputs without false triggering. The spring-loaded terminals accept 2x (0.5 to 2.5 mm²) without core-end processing or 2x (0.5 to 1.5 mm²) with ferrules, and the equivalent AWG range is 2x (20 to 14).
What the ratings mean for your circuit
The AC-15 rating of 1 A at 690 V tells you this switch can handle inductive loads — contactor coils, solenoid valves — at higher voltages without welding contacts. For DC switching, the 24 V rating is 10 A (resistive) or 6 A (likely inductive, per the at-24-V entry), dropping to 0.3 A at 220 V DC and 0.26 A at 600 V DC. That DC derating is steep: if you're switching a DC coil at 110 V, you're limited to 1 A. Contact reliability is specified at 1 faulty switching per 100 million operations at 17 V, 1 mA — that's the gold standard for direct PLC input sensing. The mechanical life is 10 million switching cycles typical, so this block outlasts most contactors it rides on. The insulation voltage is 690 V AC at pollution degree 3, with a surge voltage resistance of 6 kV. That means it's rated for industrial environments where conductive dust or humidity is present, and it can handle transient spikes common on motor circuits.
Integration notes
Snap-on mounting to a DIN rail, size S00. The block is 36 mm wide, 47.7 mm deep, and 41.5 mm tall — it shares the same footprint as the 3RH2 contactor relay series it's designed for. Two NC contacts are instantaneous (no leading or lagging delay), and one NO contact is also instantaneous. The leading contact count is zero, so all contacts switch simultaneously. Operating temperature range is -25 to +60 °C; storage from -55 to +80 °C. Front-side protection is IP20 — suitable for enclosed panels, not for washdown environments.