What it is and what it fits
The Siemens SIRIUS 3RH1921-1FE13 is an auxiliary switch block that mounts onto a contactor relay or power contactor — specifically noted for use with the 3RT1 series. It snaps onto the front of the contactor, adding one normally-open and one normally-closed contact, plus two normally-closed contacts that are rated solid-state-compatible for switching low-energy signals like PLC inputs or solid-state relay coils. The front IP20 protection keeps fingers out of the terminal area inside a control panel.
Key ratings — what they mean for fit
The switch block is rated 0.3 A at both 24 V and 60 V — that is the continuous thermal current for the auxiliary contacts, not a motor-switching figure. It means the contacts are sized for control-circuit loads: relay coils, indicator lamps, or PLC digital inputs. For higher-current auxiliary switching you would step up to the standard 10 A contacts on a larger block. The contact reliability spec — one faulty switching per 100 million operations at 17 V, 1 mA — confirms these are designed for dry-circuit logic signals where oxide films on standard contacts cause intermittent faults.
Panel integration — snap-on, screw terminals
Mounting is snap-on onto the contactor front — no tools, no DIN rail required for the block itself. The screw-type terminals accept 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) with core-end processing, or the AWG equivalents 2x (20 to 16) and 2x (18 to 14). Dimensions are 44 mm wide, 38 mm tall, 51 mm deep — the depth is the critical dimension for clearance between the contactor front and the enclosure door or busbar. Operating temperature range is -25 to +60 °C; storage range is -55 to +80 °C. Surge voltage resistance is 6 kV, and insulation voltage is 690 V AC at pollution degree 3.