The Siemens SIRIUS 3RH2911-2NF20 is an auxiliary switch block designed to snap onto the front of 3RT2.2/3/4 contactors and 3RH2 contactor relays. It adds two normally-open (NO) auxiliary contacts that are explicitly rated as solid-state compatible — meaning they handle the low-energy switching demands of PLC inputs and electronic control modules without the contact wetting issues standard silver-cadmium contacts can exhibit at milliampere levels.
Contact reliability and switching performance
The solid-state-compatible NO contacts are rated for one incorrect switching operation per 100 million cycles at 5 V, 1 mA — a figure that tells you these contacts are designed for the dry-switching environment of a digital input card, not just power contactor mirror contacts.
Spring-loaded terminals accept 2x (0.5... 1.5 mm²) with ferrule or 2x (0.5... 2.5 mm²) solid/stranded without. AWG equivalent is 2x (20... 14). The 47.7 mm depth, 36 mm width, and 41.5 mm height keep the block within the contactor's own envelope — no extra DIN-rail space consumed. Snap-on mounting onto the contactor front means no tools for installation or removal; the block clips into the same slots as the standard auxiliary switch.
Environmental and electrical ratings
Front protection is IP20 — finger-safe from the front, but the contactor body itself provides the enclosure-level IP rating. The block carries no leading or lagging contact timing (both are 0), so all NO contacts close simultaneously.