What it is and what it does
The Siemens 3RT2015-2QB42 is a SIRIUS coupling contactor in the compact S00 frame size, designed for switching loads in control circuits where the coil and main contacts share a common 24 VDC supply. It uses spring-type terminals for the magnet coil, which means no screw tightening — strip, insert, and the cage clamps the wire. The 24 V rated coil holds reliably, and the DC-13 breaking current at 24 V is 10 A, so it handles inductive DC loads like relay coils or solenoid valves without welded contacts.
Mounting and integration
Mounts via screw or snap-on onto a 35 mm DIN rail per DIN EN 60715. The mounting position is flexible: +/-180° rotation on a vertical surface, and can be tilted forward/backward by +/-22.5° on that same surface. Clearance requirements are tight: 10 mm upwards, 10 mm forwards, 10 mm downwards, and 6 mm at the side — so it fits in crowded enclosures without needing extra breathing room. The 45 mm width and 70 mm height mean it occupies one standard DIN-rail module width.
Electrical ratings and switching performance
Rated control supply voltage is 24 VDC. For DC-13 duty (switching electromagnets), the contactor breaks 10 A at 24 V, 2 A at 48 V and 60 V, 1 A at 110 V, 0.9 A at 125 V, and 0.3 A at 220 V. At 400 V AC-3 motor duty, it switches 3 A. The arcing time is 10 to 15 ms, and DC switching takes 7 to 20 ms — the spread depends on the load inductance. Maximum switching frequency depends on duty: 1,000 operations per hour at AC-1 (resistive), 750 at AC-2 and AC-3 (motor start/run), and 250 at AC-4 (plugging/inching). The main contacts are rated for 20 to 12 million operating cycles, and the typical mechanical service life is 30 million operations.
Environmental and wiring
Operates from -25 to +60 °C, stores from -55 to +80 °C. Accepts solid or stranded conductors from 0.5 to 4 mm² (single wire) or 2x (0.5 to 4 mm²) for paralleled conductors. No auxiliary switch is included on this variant — the 2QB42 suffix indicates a basic coupling contactor without add-on blocks.