What it is and where it fits
The Siemens 3RT2035-1SB30 is a SIRIUS power contactor in frame size S2, designed for switching motor loads and resistive loads in industrial control panels. It mounts on 35 mm DIN rail per DIN EN 60715 via screw or snap-on fastening, and the mounting position allows +/-180° rotation on a vertical surface plus +/-22.5° tilt forward and backward — handy when you're squeezing it into a tight enclosure. Rated coil voltage is 21-33 V DC, with a pickup threshold of 0.8 x rated value (about 16.8 V) and a dropout around 0.1 x rated value (roughly 2.1 V). Inrush current peaks at 2.2 A, holding power at 2 VA on 50/60 Hz. That's a standard DC coil draw — plan your 24 VDC supply to handle the inrush if you're ganging several contactors.
Key ratings and what they mean for your panel
This contactor is rated for continuous duty across a wide ambient temperature range: -25 to +60 °C during operation, with storage from -55 to +80 °C. That covers most indoor panel environments, including non-conditioned electrical rooms. The 55 mm width and 130 mm depth are standard for the S2 frame — check your DIN-rail clearance and door swing before committing. Mechanical life is typical at 5 million operations, and the listed MTBF is 52 years — a reliability figure that assumes proper derating and clean power. For a contactor in a pump panel cycling a few times an hour, that's a solid baseline. The main contacts are rated for switching frequencies up to 1000 cycles/hour under AC-1, AC-3, and AC-3e duty, 750 cycles/hour under AC-2, and 300 cycles/hour under AC-4. That means it's comfortable in conveyor and fan duty (AC-3) but you'll want to derate for heavy jogging or inching (AC-4). Auxiliary contacts are built in — the main contact block carries 1 NO + 1 NC configuration (18 to 1). That's enough for a feedback signal or a holding circuit without an add-on block.
Integration notes for the panel builder
Screw-type terminals on the magnet coil accept 2 x (0.5 to 1.5 mm²) or 2 x (0.75 to 2.5 mm²) solid or stranded wire. That's typical for control wiring — no special crimp tool needed, but use ferrules on stranded for a reliable connection. Clearance requirements: 10 mm upwards, 10 mm forwards, 10 mm downwards, 6 mm at the side. Those are the minimum air gaps for arc flash and heat dissipation.