What it is and where it fits
The Siemens 3RT2028-1DB40 is a SIRIUS power contactor in the Size S0 frame, built for switching motor loads and resistive circuits in control panels. It mounts on 35 mm DIN rail per DIN EN 60715, with screw and snap-on fastening, and accepts screw-type terminals for the magnet coil. The 24 VDC coil pulls in at 0.8 × rated voltage and holds across the -25 to +60 °C operating range. That's the temperature inside the enclosure — storage tolerance is wider at -55 to +80 °C, which matters if this sits in an unheated warehouse before commissioning.
Wire termination and panel clearances
Main contacts accept solid or stranded conductors from 1 to 10 mm². Auxiliary contacts take two conductors per clamp: 2 × (0.5 to 1.5 mm²) or 2 × (0.75 to 2.5 mm²). The contactor envelope is 45 mm wide, 102 mm tall, 107 mm deep. Clearance requirements: 10 mm upwards, 10 mm forwards, 10 mm downwards, and 6 mm at the sides. That 6 mm side gap is tight — if you're packing multiple contactors on a DIN rail, verify the combined heat dissipation won't exceed the derating curve. The mounting position allows ±180° rotation on a vertical surface and ±22.5° tilt forward/backward, so it fits in panels where the rail is angled.