What it is and where it fits
The Siemens 3RH2911-1FC30 is a front-mounted auxiliary switch block in the SIRIUS family, carrying three normally-open (3 NO) contacts with screw-type terminals. It snaps onto the front of 3RT2 power contactors and 3RH2 contactor relays, adding auxiliary switching capacity without expanding the DIN-rail footprint.
Switching ratings — what the numbers mean
Rated 10 A maximum, but the real-world switching capacity depends on the circuit voltage. At 24 V it handles 6 A; at 125 V also 6 A; at 230/250 V still 6 A. At 400 V the rating drops to 3 A, and at 220 V DC it manages only 0.3 A. For AC-15 inductive loads at 690 V — typical for pilot-duty control circuits — the rated value is 1 A. The DC switching curve is steep: 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, down to 0.26 A at 600 V. Match the voltage and load type to the correct column; the AC-15 rating at 690 V is the one that governs for most contactor-coil switching applications.
Mounting and wiring
Snap-on mounting to the contactor front — no tools, no DIN-rail space consumed. Dimensions are 43.7 mm deep, 36 mm wide, 37.5 mm high. Screw terminals accept 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) with core-end processing, or 2x (20 to 16) and 2x (18 to 14) AWG. The contact sequence is 1 NO leading, 1 NO leading, 1 NO leading — all three close simultaneously, no lagging or instantaneous contacts on this variant. IP20 front protection keeps fingers out of the terminal area.