What it is and what it does
The Siemens 3RH1911-2HA12 is a 4-pole auxiliary switch block from the SIRIUS family, configured as 1 normally open and 2 normally closed contacts (the fourth pole is unused in this variant). It snaps onto a DIN rail and connects via spring-loaded terminals, accepting 2x (0.5... 2.5 mm²) stranded without ferrules or 2x (0.5... 1.5 mm²) with core-end processing. The block is rated for use with contactor relays and power contactors in the same series. The contact reliability specification — one faulty switching per 100 million operations at 17 V, 1 mA — means this block is suitable for low-level logic signals in PLC or safety circuits, not just power switching. Mechanical service life is rated at 10 million switching cycles typical.
Ratings and what they mean for fit
The maximum continuous current is 10 A, but the real load capability depends on voltage and duty. For AC-15 control-circuit duty at 690 V, the rated value is 1 A — that is the figure to use when switching contactor coils or solenoid valves on a 690 V line. At lower voltages the block carries more: 6 A at 24 V, 3 A at 400 V. The DC ratings follow a similar derating curve: 10 A at 24 V DC, dropping to 0.26 A at 600 V DC. Surge voltage resistance is rated at 6 kV, and insulation voltage at 690 V AC with pollution degree 3. The IP20 protection on the front means it is protected against finger contact but not against moisture — suitable for enclosed panels only.
Panel integration notes
Snap-on mounting to a DIN rail (EN 50012 profile). Dimensions: 46 mm depth, 36.5 mm width, 37.5 mm height. The spring-loaded terminals accept AWG 20–14 for auxiliary circuits. The block is designed to mount directly alongside SIRIUS contactors and contactor relays, sharing the same rail and wiring plane.