The Siemens 3RU1146-4LB0 is a SIRIUS thermal overload relay, size S3, designed for motor protection in a control panel. The IP20 front protection means it is safe for finger contact inside an enclosure but not for washdown environments.
The 140 mm depth and 70 mm width are the critical panel-space numbers — this relay occupies a standard S3 footprint, so verify your DIN-rail clearance against the 120 mm height and the 140 mm projection. The screw-type terminals on both the main and auxiliary circuits accept stranded conductors up to 70 mm² on the main circuit and 2.5 mm² on the auxiliary side, which covers most motor branch circuits up to 160 A gG fuse coordination. The auxiliary contact ratings span 24 V to 400 V AC/DC (, –), so the N/C trip alarm can drive a PLC input or a panel lamp at the same voltage as the control circuit.
Deployment context and approvals
This relay carries ATEX approval (DMT 98 ATEX G 001,), so it is suitable for use in potentially explosive atmospheres when paired with an appropriate contactor and enclosure. The surge voltage resistance of 8 kV gives it solid margin for industrial mains transients. The mounting position is flexible — vertical surface with ±135° rotation and ±45° tilt — which helps when panel layout is tight. Per-pole power dissipation of 7 W means the relay contributes about 21 W total heat in a three-phase circuit; factor that into your enclosure thermal calculation. Shock resistance is 8g for 10 ms.
Coordination and selectivity notes
For type 1 coordination (starter may be damaged but no hazard to personnel), the limit is 250 A gG. These figures matter when you are sizing the branch circuit protection upstream of this relay and its contactor.