What this contactor is and where it fits
The Siemens 3RT1316-1BG40 is a SIRIUS power contactor in frame size S00 — the smallest in the series, designed for switching motor loads and resistive loads in control panels up to 4 kW at AC-2 duty on a 400 V line. It carries four normally-open main contacts rated 10 A in AC-12 (control-circuit duty), so it can also serve as a high-current interposing relay in PLC output circuits. The 24 VDC coil draws 3.3 W both on pickup and hold, which simplifies the DC supply budget — no inrush spike to size for. Mounting is screw-fix or snap-on onto 35 mm DIN rail per EN 50022, and the 45 mm width means it occupies one standard modular device pitch. Front and terminal faces are rated IP20, so it is suited for enclosed panel installation where accidental finger contact is the concern.
Key ratings and what they mean for your circuit
The AC-2 rating of 4 kW at 400 V is the motor-switching figure that governs real use — AC-2 covers starting and plugging of slip-ring motors, where the contactor must handle both the starting current and the breaking of the rotor circuit. For resistive or lightly inductive loads, the AC-12 rating of 10 A gives headroom. The main contacts are screw-type terminals accepting 2x 0.75 to 4 mm² solid or stranded, or 2x 20 to 14 AWG, with a single 12 AWG also allowed. Short-circuit coordination is specified with gL/gG fuses: 20 A for Type 2 coordination (no damage to the contactor after a fault) and 35 A for Type 1 (contactor may need replacement but the installation is safe). The pollution degree 3 rating means it is designed for industrial environments with conductive pollution — typical for panels without climate control. Operating temperature spans -25 to +60 °C, and the maximum altitude is 2 000 m without derating. The auxiliary contact ratings cover 10 A at 24 V down to 0.3 A at 220 V DC, which covers most DC control circuits in industrial panels.
Panel integration notes
At 72 mm deep, 57.5 mm tall, and 45 mm wide, the S00 frame fits standard 45 mm pitch DIN-rail layouts. Side-by-side mounting is permitted with a 6 mm gap to adjacent devices for heat dissipation. The screw terminals are accessible from the front, so wiring in a dense row is straightforward. The coil holding power is the same as the closing power — 3.3 W DC — which means no additional heat sink or derating for continuous energization. For a 24 VDC supply, that is about 137 mA continuous draw per contactor.