What it is and where it fits
The Siemens SIRIUS 3RT2518-1AH00 is a size S00 contactor, part of the SIRIUS family, designed for switching motor loads and resistive loads in control panels. It mounts on a 35 mm DIN rail per DIN EN 50022 using the integrated snap-on mechanism, with screw-type terminals for the coil and main circuits. The 45 mm width and 73 mm depth fit standard enclosure cutouts, and the 57.5 mm height leaves room for busbars or wiring ducts above. Side-by-side mounting is permitted, with a 6 mm lateral clearance required for thermal derating when not ganged.
Key ratings and what they mean for your circuit
The contactor carries a 24 V DC rated switching current of 10 A, dropping to 2 A at 48 V and 60 V, 1 A at 110 V, and 0.3 A at 220 V. At 230 V DC it returns to 10 A, then 3 A at 400 V, 0.8 A at 440 V, and 0.1 A at 600 V. These are the DC-1 resistive load ratings — for inductive DC loads (DC-3/DC-5) you typically derate by 50-70%, so the 24 V 10 A figure is for heaters or lamps, not solenoids or DC motors. The AC operating time is 4 to 15 ms, with an arcing time of 10 to 15 ms. The mechanical service life is rated at 30,000,000 operations typical, and the maximum switching frequency at AC-1 duty is 1,000 operations per hour. At DC the maximum switching frequency is 10,000 operations per hour. Operating temperature range is -25 to +60 °C, storage from -55 to +80 °C. The contactor can be mounted in any orientation, including +/-180° rotation on a vertical surface and +/-22.5° tilt forward/backward.
Wiring and conductor sizing
The screw-type terminals accept solid or stranded conductors: 2x 0.5 to 1.5 mm², 2x 0.75 to 2.5 mm², or 2x 4 mm². This covers most control-circuit wiring (1.5 mm² for coil leads) and main power wiring up to 4 mm² for the load circuit.