What it is and where it lands
The Siemens 3RH2911-2HA22-ZW97 is a front-mounted auxiliary switch block for the SIRIUS family, designed to snap onto 3RT2 power contactors and 3RH2 contactor relays. It carries two normally-open and two normally-closed contacts, arranged as two independent contact paths per pole, all terminated through spring-loaded terminals that accept 2x (0.5 to 2.5 mm²) stranded or solid wire without ferrules. Rated for a maximum of 10 A, the switch block delivers 6 A at 24 V and 230/250 V, 3 A at 400 V, and 0.3 A at 220 V — the voltage-specific current limits reflect the contact gap and arc-quenching design for DC and AC loads. For AC-15 inductive duty at 690 V, the rating drops to 1 A, which is the figure to check when switching contactor coils or solenoid valves on a 690 V line.
Mounting and wiring — panel fit
Snap-on mounting to the contactor front face — no tools, no DIN rail. The block measures 36 mm wide by 41.5 mm high by 47.7 mm deep, adding about 48 mm to the contactor depth. Spring-loaded terminals accept 2x (0.5 to 1.5 mm²) with ferruled ends or 2x (0.5 to 2.5 mm²) without; AWG equivalents are 2x (20 to 14). Strip length is standard for cage-clamp style — 8 to 10 mm. The front face carries IP20 protection, meaning the terminals are finger-safe but the block is not sealed against dust or moisture — keep it inside the enclosure, not on the panel door. Operating temperature range is -25 to +60 °C; storage from -55 to +80 °C.
Contact reliability and service life
Mechanical service life is rated at 10 million switching cycles typical. Contact reliability is specified as 1 faulty switching per 100 million operations at 17 V and 1 mA — relevant for low-energy signal circuits where oxide films on silver contacts can cause intermittent opens. The 6 kV surge voltage resistance (rated) covers transient overvoltages common in industrial control panels.