What it is and where it fits
The Siemens 3RT2518-2AF00 is a SIRIUS contactor in the S00 frame size, designed for switching auxiliary and control circuits up to 10 A at 24 V. It mounts via screw or snap-on onto 35 mm DIN rail per DIN EN 50022, with a width of 45 mm and depth of 73 mm, so it fits standard panel layouts without crowding adjacent devices.
Auxiliary contact ratings — what they mean for your circuit
The auxiliary switch is rated 10 A at 24 V and 230 V, 2 A at 48 V, 60 V, and 125 V, 1 A at 110 V, 3 A at 400 V, 0.8 A at 440 V, and 0.1 A at 600 V. These are the maximum continuous currents the contacts can make and break at each voltage level — so at 24 VDC you get the full 10 A, but at 600 VAC you're limited to 0.1 A. For a 24 VDC PLC output driving a contactor coil, the 10 A rating gives plenty of headroom.
Mounting and wiring details
The coil connection uses spring-type terminals, accepting 2x (0.5 to 4 mm²) solid or stranded wire. The mounting position allows ±180° rotation on a vertical surface and ±22.5° tilt forward/backward, so you can orient it for tight panel access. Side-by-side mounting is supported with a clearance of 6 mm at the side, and zero clearance upwards, forwards, backwards, and downwards.