What it is and what it does
The Siemens 3RT5044-1AC20 is a SIRIUS power contactor in the S3 frame size, designed for switching motor loads and resistive loads in industrial control panels. It carries a rated insulation voltage of 1000 V, which means it can be used in 400 V and 690 V systems with headroom for transient overvoltages (pollution degree 3). The screw-type main circuit terminals accept 2x (2.5 to 16 mm²) solid or stranded copper, or 2x (10 to 1/0 AWG).
Mounting and integration
Mounts on 35 mm or 75 mm DIN rail via screw and snap-on. The 70 mm width and 139 mm depth fit standard panel layouts — no oversize cutouts needed. Side-by-side mounting is allowed, so you can gang multiple contactors without spacing. The mounting position allows ±180° rotation on a vertical surface and ±22.5° tilt forward/backward, which helps in tight enclosures where the rail is angled.
Environmental limits
Rated for operation from -25 to +60 °C ambient, with storage from -55 to +80 °C. The operating range covers most indoor industrial environments; if the panel internal temperature exceeds 60 °C, derating applies per the manufacturer's thermal curve.