What it is and where it fits
The Siemens 3RH2911-1YA21-0MA0 is a front-mounted auxiliary switch block in the SIRIUS family, carrying 2 normally-open and 1 normally-closed contact set (31/32, 43/44, 53/54) with screw-type terminals. It snaps onto 3RT2 power contactors and 3RH2 contactor relays — no tools needed for mounting, just press it onto the front face of the device. Rated for a maximum of 10 A, the contacts are sized for control-circuit switching, not motor loads directly. The AC-15 rating at 690 V is 1 A — that's the inductive load curve for solenoid valves, contactor coils, and pilot lights in a 690 V control scheme. For DC switching, the rated values drop as voltage climbs: 10 A at 24 V DC, 6 A at 125 V DC, and 0.26 A at 600 V DC. The mechanical service life is a typical 10 million switching cycles, which outlasts most contactors it'll ride on. Contact reliability is spec'd at one faulty switching per 100 million operations at 17 V, 1 mA — important for PLC input circuits where dry switching can cause intermittent faults.
Panel fit and wiring
Snap-on mounting means it clips directly to the contactor front without extra hardware — no DIN rail needed for the switch itself, though the contactor it attaches to may be rail-mounted. Dimensions are compact: 36 mm wide, 37.5 mm high, 43.7 mm deep. The 43.7 mm depth includes the screw terminals, so account for that when planning enclosure depth. Screw 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 IP20 protection on the front means it's finger-safe but not washdown-rated — keep it inside the panel, not on the machine face. Rated insulation voltage is 690 V AC at pollution degree 3, with a surge voltage resistance of 6 kV. That covers standard 480 V and 600 V industrial panels with margin. Operating temperature range is -25 to +60 °C; storage range is -55 to +80 °C.