What it is and where it fits
The Siemens 3RT2028-1BB44 is a SIRIUS power contactor in the S0 frame size, rated for a 24 VDC coil with screw-type terminals. It mounts via screw or snap-on onto 35 mm DIN rail per DIN EN 60715, making it a direct drop-in for standard panel layouts — no need to gut the whole line if you're swapping into an existing S0 footprint.
What the ratings mean for your circuit
The coil pulls 6 A at 24 VDC inrush, then holds at a lower sealed current; the contactor switches motor loads in AC-3 duty up to 750 cycles per hour, with a maximum of 1 000 cycles/h in AC-1 resistive loads. For heavy AC-4 reversing or inching, the rate drops to 250 cycles/h — plan your duty cycle accordingly. The main contacts accept solid or stranded wire from 1 to 10 mm², and auxiliary circuits can be doubled up with 2x (0.5... 1.5 mm²) or 2x (0.75... 2.5 mm²).
Mounting and environment
The S0 contactor measures 85 mm high, 45 mm wide, and 151 mm deep. It can be mounted in any orientation on a vertical surface, including ±180° rotation and ±22.5° tilt forward/backward. Clearance requirements: 10 mm upwards, 10 mm forwards, 10 mm downwards, and 6 mm at the side. Operating temperature range is -25 to +60 °C; storage range is -55 to +80 °C.