What it is and what it does
The Siemens SIRIUS 3RT2018-2KB42-0LA0 is a size S00 power contactor with a 24 VDC coil and spring-type terminals on the magnet coil. It is designed for switching motor loads and resistive loads in control panels, with a 45 mm width that fits standard DIN-rail enclosures.
Key ratings and what they mean for your panel
The 24 VDC coil holds at nominal voltage; dropout characteristics follow the DC curve typical of SIRIUS contactors. The spring-type terminals accept a range of conductor cross-sections: 2x (0.5... 1.5 mm²), 2x (0.75... 2.5 mm²), and 2x 4 mm², which covers most control-circuit wiring in a standard panel. Size S00 means a compact footprint — 45 mm wide, 70 mm high, 121 mm deep — that leaves room for auxiliary contact blocks and overload relays on the same DIN rail. Mounting position is flexible: +/-180° rotation on a vertical surface, plus +/-22.5° tilt forward/backward, so it fits into tight enclosures without rework. Clearance distances are specified: 10 mm upwards, 10 mm forwards, 10 mm downwards, and 6 mm at the side. These matter for arc flash and heat dissipation — respect them in your layout.
Mounting and integration
Fastening is by screw and snap-on mounting onto 35 mm DIN rail per DIN EN 60715. No adapter plate needed — it clips directly onto the rail and secures with the screw for vibration resistance. The spring-type terminals reduce wiring time: strip to the required length, push in, done.