The Siemens SIRIUS 3RH2911-1NF02 is a front-mounted auxiliary switch designed for contactor relays and power contactors in the S00, S0, S2, and S3 frame sizes. It provides two normally-closed (NC) contacts that are solid-state compatible, meaning they switch reliably at the low voltage and current levels typical of PLC inputs and electronic control circuits — rated at 0.3 A across 24 V, 48 V, and 60 V. The contact reliability spec backs this up: one incorrect switching operation per 100 million cycles at 5 V, 1 mA. That is the rating that matters for a line-side PLC input that sees a dry contact closure.
Snaps onto the front of the contactor — no DIN rail required, no screws. The 36 mm width matches the contactor body, so it does not add panel width. Screw terminals accept 2x (0.5 to 1.5 mm²) solid or stranded, or 2x (0.75 to 2.5 mm²) with ferruled ends; AWG 20 to 14. Strip length is standard for screw clamps.
Electrical ratings and compliance
Rated insulation voltage 690 V at pollution degree 3, surge voltage resistance 6 kV — standard for industrial control panels up to 480/600 V line-to-line. The mirror contact feature per IEC 60947-4-1 is present when used with 3RT2.2/3/4 contactors, which means the NC position is mechanically linked to the main contacts for safety-related feedback. RoHS compliance date 2009-10-01.