S00 Auxiliary Switch for Safety-Circuit Integration
The Siemens SIRIUS 3RH1911-1HA01-ZW95 is an auxiliary switch block sized for the S00 contactor frame, snapping onto the front of the contactor relay or power contactor without tools. It carries a mirror contact per IEC 60947-4-1 when paired with a 3RT1 contactor, meaning the normally-closed (NC) contact position is mechanically linked to the main contacts — a requirement for safety-related feedback circuits that must detect contact welding. The front face is IP20, so the switch can sit on a panel door or enclosure cutout without additional finger protection. Rated operational current at AC-12 (resistive load) is 10 A maximum, with AC-15 (inductive, solenoid/contactor coil) ratings stepping down across the voltage range: 6 A at 24 V, 6 A at 230 V, 3 A at 400 V, and 1 A at 690 V. The 24 V and 230 V AC-15 ratings are identical at 6 A, which is unusual — verify the coil inrush if switching a large contactor bank at 230 V, as the 6 A figure is the steady-state rating. Contact reliability is specified at 1 faulty switching per 100 million operations at 17 V, 1 mA, confirming dry-circuit capability for PLC-level signals.
Mounting and Wiring Constraints
Snap-on front mounting onto the S00 contactor — no DIN rail required, no screws. The block adds 36.5 mm width, 41.5 mm depth, and 37.5 mm height to the assembly. Terminals accept 2 x (0.5 to 1.5 mm²) solid or 2 x (0.75 to 2.5 mm²) stranded with ferrules, or AWG 20–16 and 18–14. Wire both conductors in parallel for loop-through without a separate terminal strip. The IP20 front face means the switch can be mounted on a panel door that opens to the energized contactor — no additional cover required.