What it is and where it fits
The Siemens 3RH1911-1HA13-ZW95 is a SIRIUS auxiliary switch block with 1 normally open and 3 normally closed contacts, rated for a maximum of 10 A and designed for use with contactor relays and power contactors. It snaps onto the contactor, so panel integration is straightforward — no separate DIN-rail footprint needed beyond the contactor itself.
Key ratings and what they mean for fit
The 10 A maximum is the thermal current (Ith); the real switching capacity depends on voltage and duty. At 24 V it handles 6 A, at 230 V it also handles 6 A, and at 400 V it drops to 3 A. For DC applications the derating is steeper — at 220 V DC it's only 0.3 A. The AC-15 rating at 690 V is 1 A, which covers solenoid and contactor coil switching in that voltage class. The insulation voltage is 690 V AC at pollution degree 3, and surge voltage resistance is 6 kV — both standard for industrial control panels. Mechanical service life is 10 million switching cycles typical, and contact reliability is rated at 1 faulty switching per 100 million operations at 17 V, 1 mA — that's a low-level signal reliability spec, important if you're switching PLC inputs or sensor signals rather than power loads.
Mounting and wiring
Snap-on mounting means it clips directly onto the contactor — no tools, no extra DIN rail. 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. IP20 on the front means finger-safe in the panel but not for wet or dusty environments. Operating temperature is -25 to +60 °C; storage range is -55 to +80 °C.