The Siemens 3RH2122-1BF40 is a SIRIUS auxiliary contactor in the S00 frame size, built for control-circuit switching in motor starter and panel applications. It carries 2 NO and 2 NC instantaneous contacts, rated for a 110 V AC coil. At 24 V AC the contacts handle 10 A resistive; at 110 V AC they switch 3 A, and at 230 V AC they hold 10 A — the 110 V AC rating is the one that governs the coil circuit, while the 230 V AC figure covers the load side for common line voltages.
Mounting and Integration
Mounts via screw fixing or snap-on onto 35 mm DIN rail — the S00 frame width is 45 mm, depth 73 mm, height 57.5 mm. That keeps the panel footprint tight; you can fit several side by side on a standard rail section. The mounting position is flexible: +/-180° rotation on a vertical surface, plus +/-22.5° tilt forward or backward, so it adapts to tight enclosures or angled sub-panels. Spacing clearances: 10 mm upward, 10 mm forward, 10 mm downward, 6 mm at the side — these matter for heat dissipation and arc flash clearance.
Environmental and Compliance
Operating temperature range is -25 to +60 °C, storage -55 to +80 °C — takes the heat near a motor starter stack or inside a non-ventilated cabinet. Pollution degree 3 rating means it's suitable for industrial environments with conductive pollution or dry non-conductive pollution that becomes conductive due to condensation. The lifecycle status is current production; it's a standard catalog item from the SIRIUS line, not a phase-out or NRND part. RoHS compliance date is October 1, 2009, covering the EU substance prohibitions.
Wiring and Contact Ratings
Terminals accept 2x (0.5 to 1.5 mm²), 2x (0.75 to 2.5 mm²), or 2x 4 mm² solid or stranded wire — spring-cage or screw terminals are typical for this series, though the evidence specifies screw and snap-on mounting. The instantaneous contacts are rated for 10 A at 24 V AC and 230 V AC, 4.7 A at 60 V, 3 A at 110 V, 1.2 A at 220 V, and derated at higher voltages: 0.5 A at 440 V, 0.26 A at 600 V, 1 A at 690 V. The arcing time is 10 to 15 ms; mechanical life is 30 million operations typical.