What it is and where it fits
The Siemens 3RT2025-1AC20-ZW96 is a SIRIUS power contactor in the Size S0 frame, 45 mm wide, with a 24 V coil and screw-type terminals on both main and auxiliary circuits. It carries a built-in auxiliary switch (1 NO + 1 NC) so you don't need a separate side-mount block for basic feedback or interlock wiring. Mounting is straightforward — screw-fix or snap onto a 35 mm DIN rail per DIN EN 60715. The mounting position is flexible: ±180° rotation on a vertical surface, plus ±22.5° tilt forward/backward, which helps in tight enclosures where you're routing wires around other gear. Operating temperature range is -25 to +60 °C, storage from -55 to +80 °C, so it handles a control panel in an unheated warehouse or a rooftop unit in summer without derating concerns at the coil.
Key ratings for motor and resistive loads
For switching motor loads, the contactor is rated 10 A at 24 V and 3 hp at 230 V, which covers a standard 3 hp single-phase motor or a small three-phase motor through a contactor block. At 400 V it's rated 3 A, so it'll handle a 1.5 kW motor on a 400 V line — typical for a small conveyor or pump. Maximum mechanical switching frequency is 1 000 operations per hour for AC-1, AC-2, and AC-3 duty; AC-4 (plugging/inching) is limited to 300 operations per hour. Mechanical life is rated at 10 000 000 operations typical, so it's built for high-cycle applications like packaging lines or machine tools. Wire termination accepts solid or stranded conductors from 1 to 10 mm², or two conductors per terminal from 0.5 to 2.5 mm². That covers most panel wiring from 14 AWG to 8 AWG without needing ferrule adapters.
Sourcing and lifecycle
For BOM freeze or long-term planning, the SIRIUS 3RT2 series is a mature platform with broad installed base. If you're sourcing for a new panel design, the 45 mm width and Size S0 footprint match the standard DIN-rail grid, and the screw terminals are field-serviceable without special tools.
Panel integration notes
Clearance distances: 10 mm upwards, 10 mm forwards, 10 mm downwards, 6 mm at the side. That's tight enough to pack contactors side-by-side on a DIN rail in a 600 mm wide enclosure. Depth is 97 mm, so it fits a standard 200 mm deep panel with room for wiring ducts. Arcing time is 10 ms, and the contactor is rated for AC switching with a 4 to 16 ms operating time. The screw terminals on the magnet coil are standard M3.5 or similar, so a Pozidriv #2 or flathead is all you need for field replacement.