What it is and where it fits
The Siemens SIRIUS 3RH2911-2HA20-ZW97 is an auxiliary switch block that mounts on the front of 3RT2 contactors and 3RH2 contactor relays. It provides two normally open (2 NO) instantaneous contacts, wired via spring-loaded terminals that accept 2x (0.5 to 1.5 mm²) with ferrule or 2x (0.5 to 2.5 mm²) solid, or 2x (20 to 14 AWG). The snap-on fastening method means it clips directly onto the contactor front without tools, adding no extra DIN-rail width — useful when panel fill factor is tight.
What the ratings mean for the panel
The headline ratings here are the contact current values across different voltages and duty categories. At 24 V the contacts are rated 10 A, dropping to 6 A at 230/250 V AC and 3 A at 400 V — these are the thermal current limits for general-purpose switching. For inductive loads under AC-15 duty (solenoid valves, contactor coils), the rating is 1 A at 690 V, which is the figure that governs most control-circuit applications in 400/480 V panels. 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 the typical industrial panel environment without needing extra creepage distance. Mechanical life is 10 million switching cycles typical, and contact reliability is specified as 1 faulty switching per 100 million operations at 17 V, 1 mA — that's the gold-plated low-level signal reliability figure, important if this switch carries PLC inputs or safety circuit feedback at low voltage.
Deployment context
This block snaps onto the front of a SIRIUS 3RT2 contactor or 3RH2 contactor relay, so it adds no additional panel width — the existing contactor's DIN-rail footprint stays unchanged. The spring-loaded terminals save wiring time compared to screw terminals, and the IP20 front protection means it's suitable for enclosed panels where no one touches live parts. Operating temperature range is -25 to +60 °C, storage -55 to +80 °C.