Auxiliary Switch Block for SIRIUS Contactors
The Siemens 3RH1911-2FA40-0MC0 is a SIRIUS auxiliary switch block that mounts on the front of 3RT101..-.K...-0LA0 contactors, adding four normally-open (4 NO) instantaneous contacts rated 10 A maximum. It snaps onto 35 mm DIN rail and connects via spring-loaded terminals — no screwdriver needed for the control wiring.
What the Ratings Mean for Fit
The 10 A maximum is a thermal (AC-1) rating; the real-world switching capacity depends on voltage and load type. At 24 V it handles 6 A, at 230 V it handles 6 A, and at 400 V it handles 3 A. For DC loads the derating is steeper: 6 A at 24 V, 2 A at 60 V, 0.3 A at 220 V. The AC-15 rating at 690 V is 1 A — that's the inductive pilot-duty limit for solenoid valves or contactor coils in a 690 V control circuit. Four NO contacts means this block provides four independent form-A (normally-open) switching channels. The contact reliability spec — one faulty switching per 100 million operations at 17 V, 1 mA — tells you it's designed for PLC-level dry circuits, not just power switching. Mechanical life is 10 million operating cycles typical. IP20 on the front means finger-safe from the panel face, but the rear is open to the contactor body — standard for auxiliary blocks that live inside an enclosed panel. The insulation voltage is 690 V at pollution degree 3, with a surge withstand of 6 kV, which covers most industrial control panels up to 480/690 V line-to-line.
Mounting and Wiring
Snap-on mounting onto 35 mm DIN rail. Dimensions are 46 mm deep, 36.5 mm wide, 37.5 mm high — it adds about 37 mm of height to the contactor stack. Spring-loaded terminals accept 2× (0.5 to 2.5 mm²) without ferrules, or 2× (0.5 to 1.5 mm²) with core-end processing. AWG range is 2× (20 to 14).