What it is and what it does
The Siemens 3RT2018-2BB42-1AA0 is a SIRIUS power contactor in the Size S00 frame, designed for switching motor and resistive loads in control panels. The 24 V DC coil pulls in at 0.8 of rated voltage and drops out at 1.1 of rated voltage, per the datasheet figures. Spring-type terminals on the coil save a wiring step versus screw-clamp variants — no torquing, just strip and insert.
Ratings and what they mean for fit
Main contacts are rated for 20 A through 12 A depending on duty category — the AC-1 resistive load curve is the highest, while AC-3 motor switching and AC-4 inching/jogging draw lower continuous ratings. For DC-13 solenoid loads, the contactor breaks 10 A at 24 V, 2 A at 48 V, and 0.3 A at 220 V, so it handles small DC brake coils or control transformers within those limits. The mechanical life is 30 million operations, and the maximum switching frequency varies by duty: 1 000 cycles/hour at AC-1, 750 at AC-2/AC-3, and 250 at AC-4 — the AC-4 figure governs if the application includes plugging or inching.
Mounting and integration
The 45 mm wide body snaps onto a 35 mm DIN rail per DIN EN 60715, or can be screw-mounted. Mounting position is standing on a horizontal surface. Clearance distances: 10 mm upward, 10 mm forward, 10 mm downward, 6 mm at the sides. Wire range for main and auxiliary circuits is 0.5 to 4 mm² solid or stranded, with 2 x (0.5 to 4 mm²) permissible for looping. Operating temperature range is -25 to +60 °C; storage range is -55 to +80 °C.