The Siemens SIRIUS 3RH2911-4NF11 is a front-mounted auxiliary switch block designed specifically for the 3RT2 power contactor and 3RH2 contactor relay series. It snaps onto the front of contactors in sizes S00, S0, S2, and S3, adding one normally-open and one normally-closed instantaneous auxiliary contact to the assembly. The contacts are rated as solid-state compatible, meaning they are designed for reliable low-level switching — the spec calls out one incorrect switching operation per 100 million operations at 5 V and 1 mA. This makes the block suitable for directly driving PLC inputs or solid-state logic without intermediate relays.
These values confirm it is rated for the same voltage class as the SIRIUS contactor line it mounts to — no derating needed when used on 400 V or 690 V distribution. The contacts are rated for 0.3 A at 24 V, 48 V, and 60 V. This is the continuous current rating for the auxiliary circuit — adequate for signaling and control loads, not for power switching. The block is a mirror contact per IEC 60947-4-1 when used with specific 3RT2 contactor variants. This means the NC contact mechanically mirrors the main contact position — critical for safety circuits where you need positive confirmation that the main contacts are open before allowing access.
Physical Integration and Wiring
The block measures 36 mm wide, 37.5 mm high, and 43.7 mm deep — it adds roughly 44 mm to the front projection of the contactor. It snaps onto the contactor front without tools and does not increase the DIN-rail footprint. Termination is via ring cable lug connection — the wire is crimped to a ring terminal and bolted to the contact screw. This is a vibration-resistant connection typical for panel builds where maintenance access is infrequent. The front protection class is IP00, so the block is intended for installation inside an enclosure — not for exposed or washdown environments.
No adapter or wiring change is needed — it drops into the existing front slot.