The Siemens 3RH2911-1LA20 is a front-mounted auxiliary switch block for the SIRIUS contactor family, specifically designed to snap onto 3RT2 power contactors and 3RH2 contactor relays. It adds two normally-open (NO) auxiliary contacts — wired as terminals 73/74 and 83/84 — with screw-type terminations and top cable entry. The real-world switching capacity depends on the voltage and duty: at 24 V it's rated 6 A in AC-15, at 110 V it drops to 1 A, and at 690 V AC-15 it's still good for 1 A. That 690 V figure matters for panels running 690 V line supplies — common in heavy industrial and mining installations. The mechanical life is 10 million cycles, so this block outlasts most contactor bodies it rides on.
Snap-on mounting to the contactor front face — no tools needed, no DIN rail space consumed. The block measures 36 mm wide by 37.5 mm tall by 43.7 mm deep, which keeps the overall contactor-plus-block envelope compact for dense panel layouts. Wiring acceptance: screw terminals take 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) with core end processing, or 2x (20 to 16 AWG) and 2x (18 to 14 AWG) for stranded. IP20 on the front face means finger-safe when installed in a closed panel — standard for control cabinets.
Current ratings by voltage — the full picture
The block carries two sets of current ratings: one for general switching and one for AC-15 duty (solenoid/contactor coil loads). For general use: 10 A at 24 V, 6 A at 60 V, 1 A at 110 V, 0.3 A at 220 V, 3 A at 400 V. For AC-15 at 690 V, it's rated 1 A — that's the inductive load curve for pilot duty. That PD3 rating means it's suitable for the conductive environment inside an industrial control panel without conformal coating.