What It Is and Where It Fits
The Siemens 3RT2526-1BP40 is a SIRIUS contactor in the S0 frame size, designed for switching motor loads and resistive loads in industrial control panels. It mounts via screw and snap-on onto 35 mm DIN rail per DIN EN 50022, and the mounting position allows +/-180° rotation on a vertical surface plus +/-22.5° tilt forward and backward — useful when you're squeezing it into a crowded enclosure and the busbars run an odd angle.
Key Ratings and What They Mean for Your Panel
The coil is rated 230 V AC, with a pickup threshold of 0.8 x rated value (184 V) and a drop-out of 0.55 x rated value (126.5 V) — so if your control transformer sags under load, this contactor stays pulled in until the voltage drops below 126 V. The coil's full-scale value is 1.1 x rated (253 V), which is the maximum continuous overvoltage it can take without cooking the winding. The auxiliary switch (built-in, screw-type terminals) handles 10 A at 24 V and 230 V AC, but derates significantly at higher voltages: 3 A at 400 V, 1 A at 690 V. That 10 A at 230 V is the number you'll use most — it's enough to drive a PLC input or a small relay coil directly, but if you're switching a 690 V motor contactor's aux, you're limited to 1 A. The mechanical endurance is rated at 10,000,000 operations typical, so this contactor will outlast most panels if the switching frequency stays under 5,000 cycles per hour (AC load) or 1,000 cycles per hour at AC-1 maximum. The arcing time is 10 ms, and the DC operating time (closing + opening) is 15 to 18 ms — fast enough for most sequencing, but if you're coordinating with a fast semiconductor output, you'll want to account for that 10 ms arc extinction window.
Physical Fit and Wiring
Dimensions: 85 mm high, 61 mm wide, 107 mm deep — the S0 footprint is compact enough for a 4-wide section on a DIN rail, but the 107 mm depth means you need at least 120 mm clearance from the backplane to the enclosure door. The screw terminals accept 2x (0.5 to 1.5 mm²) solid or stranded on the smaller pair, and 2x (0.75 to 2.5 mm²) on the larger pair — standard for control wiring up to 14 AWG. Clearance distances: 0 mm on all sides except 6 mm at the side, so you can butt multiple contactors side-by-side without extra spacing, which saves rail space.
Environmental Limits
Operating temperature range is -25 to +60 °C, storage range is -55 to +80 °C. The storage range is wider because the contactor isn't switching under load — it's just sitting on a shelf. If your panel is in a non-climate-controlled warehouse that hits -30 °C, this contactor will still work, but the coil might pull a bit more inrush current until it warms up.