What it is and what it fits
The Siemens 3RT2025-2KC80 is a SIRIUS S0 coupling contactor — a compact DC-switching device with a 24 VDC coil and spring-type terminals on the magnet coil. It's sized for control circuits that need to switch DC loads up to 10 A at 24 V, 2 A at 48 V, 2 A at 60 V, 1 A at 110 V, 0.9 A at 125 V, 0.3 A at 220 V, and 3 A at 400 V. The S0 frame keeps the footprint tight at 45 mm wide, 102 mm tall, and 107 mm deep — a standard slot on a 35 mm DIN rail per DIN EN 60715.
Mounting and wiring
Mounts via screw or snap-on onto 35 mm standard mounting rail per DIN EN 60715. The mounting position is flexible: +/-180° rotation on a vertical surface, and can be tilted forward/backward by +/- 22.5° on a vertical surface. Clearance distances: 10 mm upwards, 10 mm forwards, 10 mm downwards, and 6 mm at the side. Solid conductors from 1 to 10 mm², stranded from 1 to 10 mm², and 2x (0.5 to 2.5 mm²) for solid or stranded. Spring-type terminals on the magnet coil — no screw torque to check, just strip and push.
Switching frequency by duty class
Maximum switching frequency varies by duty: 1,000 1/h for AC-1, AC-2, AC-3, and AC-3e; drops to 300 1/h for AC-4. The AC-4 limit is the one that bites on reversing or inching applications — if your cycle rate pushes past 300 per hour, this contactor will overheat. Mechanical life is typical 10,000,000 operations.
Environmental limits
Operating temperature range -25 to +60 °C; storage range -55 to +80 °C. The storage limit is for handling and shelf life, not running — don't let a panel sit in a freezing warehouse and expect the contactor to pull in at -30 °C without pre-heating the coil.