What it is and what it does
The Siemens 3RH2911-2XB22-0MA0 is a front-mounted auxiliary switch block in the SIRIUS family, designed to snap onto 3RT2 power contactors and 3RH2 contactor relays. It provides 2 normally-open and 2 normally-closed auxiliary contacts — one NO is leading, one NC is lagging — giving you sequenced signal feedback for interlocking or status indication in a control panel. Rated for a maximum of 10 A, the switching capacity depends heavily on the circuit voltage. At 24 V it handles 6 A (AC-15 at 690 V is rated 1 A). The insulation voltage is 690 V with pollution degree 3, and the contacts are surge-tested to 6 kV — so it's built for industrial environments where voltage transients are common. The spring-loaded terminals accept 2x (0.5 to 1.5 mm²) with ferrule, or 2x (0.5 to 2.5 mm²) solid, or 2x AWG 20–14. That means you can land two conductors per terminal without a screwdriver — useful when daisy-chaining auxiliary supply or signal loops.
Mounting and integration
Snap-on mounting directly onto the front of the 3RT2 or 3RH2 base unit — no tools, no DIN rail. The block is 36 mm wide, 47.7 mm deep, and 41.5 mm high, so it stays within the contactor envelope. IP20 on the front means it's protected against finger contact but not washdown; keep it inside a closed panel. Two instantaneous contacts plus one leading NO and one lagging NC let you wire a feedback path that closes before the main poles or opens after — useful for safety interlock sequences or to signal a 'ready' state ahead of the power circuit.
Switching capacity breakdown
The auxiliary contacts are rated for resistive and inductive loads across a wide voltage range. At 24 V DC: 6 A. At 60 V DC: 2 A. At 110 V DC: 1 A. At 125 V DC: 6 A. At 220 V DC: 0.3 A. At 230 V AC: 6 A. At 250 V AC: 6 A. At 400 V AC: 3 A. The AC-15 rating at 690 V is 1 A — that's the inductive contactor-coil switching duty at the highest voltage. Contact reliability is specified at 1 faulty switching per 100 million operations at 17 V, 1 mA — a dry-circuit rating that matters for PLC-level signals where oxide films on silver contacts can cause intermittent opens. Mechanical life is 10 million switching cycles typical.