The Siemens SIRIUS 3RH1911-1MA20 is an auxiliary switch block with 2 normally open contacts, designed for snap-on mounting onto size S00 contactor relays and power contactors. It carries a maximum thermal current of 10 A, with voltage-dependent ratings that define its real-world switching capability: 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. The AC-15 rating at 690 V is 1 A. This is not a generic accessory — the contact reliability spec (one faulty switching per 100 million operations at 17 V, 5 mA) tells you it's built for signal-level integrity in control circuits, not just power switching.
Panel integration and wiring
Snap-on mounting onto a 35 mm DIN rail or directly onto the S00 contactor body. The screw-type terminals accept 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. Depth is 41.5 mm, width 36.5 mm, height 37.5 mm — compact enough to fit alongside the contactor without crowding adjacent devices. IP20 on the front means it's protected against finger contact but not moisture; keep it inside a rated enclosure.
What the ratings mean for your circuit
The voltage-dependent current table is the key selection tool. At 24 VDC the contacts handle 6 A; at 125 VDC it's also 6 A, but at 220 VDC it drops to 0.3 A. The AC-15 rating of 1 A at 690 V governs solenoid and contactor coil switching in higher-voltage control circuits. The insulation voltage is rated 690 V with pollution degree 3, and surge voltage resistance is 6 kV — this block is designed for industrial environments with transient stress. Mechanical life is 10 million switching cycles typical; the contact reliability figure (one error per 100 million at 17 V, 5 mA) means it's trustworthy for PLC-level signals where a dry contact must close every time.