What this part is and what it does
The Siemens SIRIUS 3RH1911-1HA12 is a 4-pole auxiliary switch block with 1 normally open and 2 normally closed contacts, designed for snap-on mounting onto contactor relays and power contactors in the SIRIUS family. Rated for a maximum of 10 A, the switching current varies significantly with voltage: 6 A at 24 V, 6 A at 125 V, 6 A at 230 V, 6 A at 250 V, 3 A at 400 V, and 0.3 A at 220 V. At AC-15 duty up to 690 V it is rated at 1 A. The block uses screw-type terminals accepting 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) with core end processing, or 2x (20 to 16) and 2x (18 to 14) AWG for auxiliary circuits.
Key ratings and what they mean for fit
The 10 A maximum rating governs the resistive load curve; the voltage-specific ratings (6 A at 24 V, 3 A at 400 V, etc.) define the inductive switching capability at each control voltage level. For a 24 VDC control circuit, the 6 A rating is the one that determines whether this block handles the inrush of downstream contactor coils. With an insulation voltage of 690 V AC (degree of pollution 3) and a surge voltage resistance of 6 kV, the block is suitable for 400 V line-to-line panels common in European industrial installations. The IP20 front protection means it is safe for finger contact inside an enclosed panel but not for washdown environments. Mechanical service life is rated at 10 million operating cycles typical, with contact reliability of one faulty switching per 100 million operations at 17 V, 1 mA — a figure that matters for PLC-level signal switching where dry-contact reliability is critical.
Panel integration and wiring
Snap-on mounting onto 35 mm DIN rail or directly onto the contactor relay. Dimensions are 36.5 mm wide, 41.5 mm deep, and 37.5 mm high — a compact footprint that fits standard SIRIUS contactor relay envelopes without consuming additional DIN rail space. Operating temperature range is -25 to +60 °C; storage range is -55 to +80 °C. The storage limit governs handling and transport, not running conditions.