What it is and what it does
The Siemens 3RH1911-1FA20-ZX95 is a SIRIUS auxiliary switch block that adds two normally-open (NO) instantaneous contacts to a contactor relay or power contactor in the S00 frame size. It snaps onto the front of the base device, giving you extra signaling or interlocking without additional wiring space on the rail. Rated for a maximum of 10 A, with contact reliability specified at one incorrect switching operation per 100 million cycles at 17 V and 5 mA — meaning it handles both power-level pilot duty and low-level logic signals without nuisance failures.
Key ratings and what they mean for fit
The 2 NO contacts are rated across multiple voltage levels: 6 A at 24 V, 6 A at 125 V, 6 A at 230 V, and 3 A at 400 V. These are the AC-15 / utilization-category figures that govern inductive pilot-duty loads like contactor coils and solenoid valves. The 0.3 A rating at 220 V and 1.2 A at 220 V (two separate entries) reflect different duty curves — the lower figure likely applies to DC switching, the higher to AC. For DC loads, the 24 V rating of 10 A and the 60 V rating of 4.7 A give you the practical break capacity. The block is IP20 on the front. Surge voltage resistance is 6 kV. Operating temperature spans -25 to +60 °C, storage from -55 to +80 °C. The mechanical service life is 10 million switching cycles typical, which is the contactor's own mechanical endurance with this block attached.
Mounting and wiring
Snap-on mounting onto the contactor front, no DIN rail space consumed. 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. The block dimensions are 36.5 mm wide, 37.5 mm high, and 41.5 mm deep — it adds minimal projection beyond the contactor face.