What it is and what it does
The Siemens SIRIUS 3RT2015-1SB42 is a Size S00 coupling contactor — a 24 VDC coil, screw-type terminal block with a 45 mm wide footprint that wires up clean on a 35 mm DIN rail. This is the part you reach for when you need to switch a DC load in a control panel and the coil voltage is fixed at 24 VDC. The contactor is rated for 10 A at 24 VDC, 2 A at 48 VDC, and 0.75 hp at 230 V, so it handles small motors, solenoid valves, and signal-level loads within a compact envelope.
What the ratings mean for fit
The 45 mm width on the DIN rail is the first fit check — it occupies one standard module. The screw terminals accept solid or stranded wire from 0.5 to 4 mm², and can take two conductors per clamp (2x 0.5-1.5 mm², 2x 0.75-2.5 mm², or 2x 4 mm²). That means you can daisy-chain a feed-through without an extra terminal block, which keeps the wiring channel clean. The contactor has no built-in auxiliary switch, so if you need a feedback signal to a PLC input, you add a separate auxiliary contact block.
Switching performance and thermal limits
The mechanical life is rated at 30,000,000 cycles typical, so this contactor will outlast most panels. The maximum switching frequency depends on the duty class: 1,000 cycles per hour for AC-1 resistive loads, 750 cycles per hour for AC-2 and AC-3 motor starts, and 250 cycles per hour for AC-4 plugging or inching duty. The operating temperature range is -25 to +60 °C, with storage from -55 to +80 °C. The coil pick-up voltage is 0.85 x rated (20.4 VDC) and drop-out is 1.85 x rated (44.4 VDC), so it holds in during a brownout but drops cleanly when the control voltage disappears.
Mounting and clearance
Mounts via screw or snap-on onto 35 mm DIN rail per DIN EN 60715. The mounting position is flexible — the contactor can be rotated ±180° on a vertical surface, and tilted forward/backward ±22.5°. For heat dissipation, maintain at least 10 mm clearance upward, downward, and forward, and 6 mm at the sides. The depth is 73 mm, which fits standard 80 mm deep enclosures with room for wiring.