What it is and what fits
The Siemens SIRIUS 3RT2027-2BB40-0CC0 is a size S0 power contactor with a 24 VDC coil and spring-type terminals on the magnet coil. It's rated for 24 VDC at 10 A on the main contacts and includes an auxiliary switch. The coil pickup threshold is 0.8 x rated value — so at 19.2 VDC it pulls in cleanly. Mounting is screw or snap-on onto 35 mm DIN rail per DIN EN 60715. The mounting position is flexible — ±180° rotation on a vertical surface, and can be tilted forward/backward ±22.5°. That's handy when you're shoehorning it into a crowded panel and the rail isn't perfectly level.
Clearances and wiring
Keep these minimum clearances to adjacent metalwork: 10 mm upwards, 10 mm forwards, 10 mm downwards, and 6 mm at the sides. The contactor is 45 mm wide, 102 mm tall, and 107 mm deep — standard S0 footprint, so it'll drop into any panel laid out for that frame size. Main contact wiring accepts solid or stranded conductors from 1 to 10 mm². For auxiliary circuits, two conductors of 0.5 to 2.5 mm² each fit the same terminal. Spring terminals mean no screw tightening — strip, push, done. That saves time on a line-down swap.
Duty cycles and thermal limits
Maximum switching rates: 1000 operations per hour at AC-1, 750/h at AC-2 and AC-3, and 250/h at AC-4. The AC-3e rating matches the AC-3 rate at 750/h. Operating temperature range is -25 to +60 °C; storage range is -55 to +80 °C. Mechanical life is typical 10 million operations.