What the ratings mean for fit
The Siemens 3RT2325-2BF40 is a SIRIUS contactor in the S0 frame size, designed for switching motor loads and resistive circuits in industrial control panels. Its 110 V DC coil pulls in at 80% of rated voltage and drops out at 110% — the DC coil holds steady without the hum of an AC coil, but the operating time of 15–18 ms and arcing time of 10 ms mean the contactor's switching speed is fixed; if your application needs faster break, you'd look at a DC-rated semiconductor switch instead. The spring-type terminals accept 2x 0.5–2.5 mm² solid or 1–10 mm² stranded — that covers most control-wiring gauges, but if you're paralleling heavy power feeds, the 10 mm² stranded limit is the ceiling.
Mounting and integration
Mounts via screw or snap-on onto 35 mm DIN rail per DIN EN 60715. The S0 footprint is 60 mm wide, 102 mm tall, 107 mm deep. Clearance requirements: 10 mm upwards, 10 mm forwards, 10 mm downwards, 6 mm at the side. Mounting position allows ±180° rotation on a vertical surface and ±22.5° tilt forward/backward — useful when the panel layout forces an unconventional orientation. The contactor accepts up to two attachable auxiliary switch blocks; the base unit already carries one auxiliary switch.
Switching capacity and thermal limits
Main contacts rated for AC-3 duty at 18 A — that's the motor-switching current at 400 V. DC switching ratings are given per voltage: 10 A at 24 V, 2 A at 48 V, 6 A at 60 V, 1 A at 110 V, 0.9 A at 125 V, 0.3 A at 220 V, 0.1 A at 600 V, 1 A at 690 V. For AC loads: 10 A at 230 V, 3 A at 400 V, 2 A at 500 V. Mechanical life is 10 million operations typical. Operating temperature range -25 to +60 °C; storage -55 to +80 °C.