What it is and where it fits
The Siemens 3RT2015-2WB42 is a SIRIUS coupling contactor in the compact Size S00 frame, designed to switch loads on a 24 VDC coil. It's built for control-panel duty — screws or snaps onto a 35 mm DIN rail per DIN EN 60715, and the mounting position is flexible: you can rotate it ±180° on a vertical surface or tilt it ±22.5° forward or back. The coil pulls in at 85% of rated voltage (20.4 VDC) and holds steady across a -25 to +60 °C operating range — fine for most industrial enclosures, though you'll want to keep it out of direct heat plumes. Spring-type terminals accept solid or stranded wire from 0.5 to 4 mm², and you can double up two conductors of the same size in one clamp.
Key ratings and what they mean for your circuit
The main contacts are rated for 10 A at 24 V, 3 A at 400 V, and the AC-1 resistive load curve goes to 20 A across the 20–12 AWG range. For motor switching, the AC-3 duty cycle tops out at 750 operations per hour — enough for a conveyor or pump start, but not for frequent jogging. The AC-4 rating drops to 250 ops/hour, which tells you this contactor isn't built for heavy inching or plugging. Mechanical life is rated at 30 million operations typical — that's a long, quiet run in a standard panel. Arcing time runs 10 to 15 ms, and the DC dropout range is 5 to 20 ms, so you get a clean break without excessive chatter. Clearance around the contactor matters: allow 10 mm above and below, 6 mm to the side, and 10 mm forward for arc dissipation and airflow. Depth is 121 mm, width 45 mm, height 70 mm — it tucks into a tight DIN-rail row.