The Siemens 3RH2911-2FC22 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 contacts — the NO contacts are leading (close first), the NC contacts are lagging (open last), which matters when sequencing control signals during contactor pick-up and drop-out. The leading/lagging arrangement prevents momentary bridging between NO and NC circuits on the same contactor. Rated for a maximum of 10 A, with AC-15 utilization at 690 V carrying 1 A. Snap-on mounting means it clips directly to the contactor front without tools, occupying a 36 mm wide footprint and projecting 47.7 mm forward from the contactor face. The spring-loaded terminals accept 2x 0.5–2.5 mm² stranded without ferrules, or 2x 0.5–1.5 mm² with ferruled ends — no screwdriver needed for termination, which speeds panel wiring.
Switching capacity across voltage ranges
For DC switching at 24 V, the contacts handle 6 A; at 60 V, 2 A; at 110 V, 1 A; at 220 V, 0.3 A. For AC loads at 230/250 V, the rating is 6 A; at 400 V, 3 A. These derating curves reflect arc extinction limits — a buyer selecting this block for a 24 VDC pilot circuit gets full 6 A capacity, but the same block on a 220 VDC solenoid drops to 0.3 A. A second set of rated values (likely at a different duty cycle or temperature) shows 10 A at 24 V, 4.7 A at 60 V, 3 A at 110 V, 1.2 A at 220 V, 0.5 A at 440 V, and 0.26 A at 600 V. The higher 24 V figure matches the 10 A maximum, but the 60 V and 110 V figures are lower than the first set — the lower numbers likely apply at elevated ambient temperature or higher switching frequency. Always verify the specific duty cycle for your application.
For a critical spare holding on a line using 3RT2 contactors, this block is the correct front-mounted auxiliary. The spring-loaded terminal version (2FC22 suffix) is the tool-less wiring variant — if your existing install uses screw terminals, the 2FC22 is a direct mechanical fit but requires a different termination method. Ordering the spring-clamp version for a screw-terminal panel is fine; just ensure your wire ferrules or solid conductors match the 0.5–2.5 mm² range.
Surge voltage resistance is rated at 6 kV, and insulation voltage at 690 V AC with pollution degree 3.