What this part is and what it does
The Siemens SIRIUS 3RH1911-1FA40-ZW95 is an auxiliary switch block with four normally open (NO) contacts, rated for 10 A maximum, designed for use with contactor relays and power contactors in the SIRIUS family. It snaps onto the contactor via the standard mounting interface — no tools needed for installation, but verify the latch is fully engaged before energizing. The screw-type terminals on this block accept 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) conductors with core end processing, or 2x (20 to 16) and 2x (18 to 14) AWG for auxiliary wiring. The contact reliability rating — one faulty switching per 100 million operations at 17 V and 1 mA — tells you this block handles low-energy signal circuits without the intermittent failures that plague lesser contacts. That matters when the auxiliary contact feeds a PLC input or a safety relay: you want it to close every time, not just most times. Mechanical service life is rated at 10 million switching cycles typical. The operating temperature range is -25 to +60 °C, with storage from -55 to +80 °C. Surge voltage resistance is 6 kV, and the insulation voltage is rated at 690 V AC with pollution degree 3.
Mounting and integration
Snap-on mounting onto the contactor. The block measures 36.5 mm wide, 37.5 mm high, and 41.5 mm deep. IP20 on the front protects against finger contact.
Contact ratings across voltages
The maximum continuous current is 10 A, but the switching capacity varies significantly with voltage. At 24 V DC the block is rated for 6 A, dropping to 0.3 A at 220 V DC. For AC loads at 230 V it handles 6 A, and at 400 V it is rated for 3 A. At AC-15 duty (inductive loads typical for contactor coils and solenoid valves) at 690 V it is rated for 1 A. Always verify the switching current at your specific operating voltage — the 10 A maximum is only achievable at low voltages.