What it is and where it fits
The Siemens SIRIUS 3RH1431-1BF40 is an auxiliary contactor — a switching device that extends the contact set of a main contactor or provides interlocking in a control circuit. It carries 3 normally open and 1 normally closed instantaneous contacts, with a 110 VDC coil. Sized to the S00 frame, it mates directly with S00 contactors like the 3RT1 series for a compact, ganged assembly on a DIN rail or screw panel.
What the ratings mean for your circuit
The coil pulls in at 110 VDC, consuming 3.2 W both during pick-up and hold — no economizer circuit needed. The contacts are rated for switching at different voltages: 10 A at 24 V, 6 A at 230 V, 3 A at 400 V, and 1 A at 690 V. These are the maximum continuous currents the contacts can make and break under resistive (AC-1) duty. For motor or inductive loads, derate per the AC-15 utilization category typical for auxiliary contacts. The surge voltage resistance is 6 kV, which means the contactor handles transient overvoltages common in industrial control panels without flashover.
Mounting and wiring
Mounts by screw or snap-on to a 35 mm DIN rail. The mounting position is flexible: +/-180° rotation on a vertical surface, plus +/-22.5° tilt forward/backward. Wire terminals accept solid conductors: 2x 0.5...1.5 mm², 2x 0.75...2.5 mm², or 2x 4 mm². The front face is IP20, so it's protected against finger contact but not against moisture — keep it inside a rated enclosure.