What it is and what it does
The Siemens SIRIUS 3RT1316-2BF40 is a size S00 power contactor with four normally-open main contacts and a 110 V DC coil. It is designed for switching motor loads in control panels, with an AC-2 rating of 4 kW at 400 V — the duty class for slip-ring motors, where the contactor makes and breaks the rotor circuit under load. The 3.3 W DC holding power means the coil stays cool in continuous duty, and the 30 million mechanical cycles typical life gives it a long service interval in high-cycle applications like conveyor or pump stations.
Mounting and integration
Mounts via screw or snap-on onto 35 mm DIN rail per EN 50022. The 45 mm width and 72 mm depth fit standard enclosure layouts — side-by-side mounting is permitted, with a 6 mm air gap to adjacent devices for heat dissipation. Spring-loaded terminals on the main circuit accept 2x (0.25... 2.5 mm²) solid or stranded wire, or 2x (0.25... 1.5 mm²) finely stranded with ferrules. No screw torque to verify; strip and push. The IP20 finger-safe front terminals mean the panel cover can be open for commissioning without exposed live parts.
Coordination and protection
For Type 1 coordination (no damage to the contactor after a short circuit, but it may need replacement), the required upstream fuse is gL/gG 35 A. For Type 2 coordination (contactor remains operational after a fault), use gL/gG 20 A. This is the fusing spec for the main circuit; the contactor itself has no integral overload relay — pair it with a separate SIRIUS overload (e.g., 3RU series) for motor protection. Pollution degree 3 (conductive pollution or dry non-conductive that becomes conductive) means it is suited for industrial control panels, not clean-room or sealed environments.