What this auxiliary switch block does
The Siemens 3RH2911-2NP22-0MC0 is a front-mounted auxiliary switch block for contactors, delivering 2 normally-open and 2 normally-closed contacts in a 36 mm wide housing that snaps onto the contactor without tools. It's designed for solid-state compatible switching — one NO and one NC contact are optimised for low-level signals, meaning a PLC input reading a 5 V, 1 mA signal won't see intermittent opens over the block's 5 million mechanical cycle life.
Wiring and termination reality
No screwdriver needed for termination; strip, push, and the cage holds. The contact arrangement is labelled 53/54 (NO), 61/62 (NC), 71/72 (NC), 83/84 (NO) on the block face, matching standard Siemens numbering. Leading and lagging contacts are both zero — all four switch simultaneously.
Where it mounts and what it tolerates
Snap-on mounting to the contactor front — no DIN rail required. The block fits Siemens 3RT102 and 3RT103 contactors via adapter kits 3RT2926-4NA00 or 3RT2936-4NA00 respectively. Rated insulation voltage 690 V at pollution degree 3, surge voltage resistance 6 kV.